Power Jack grid tie inverters

[rama]

Hi there,
I've been hearing a lot about these Power Jack grid tie inverters that are sold on eBay. It's really strange to me to see their so-called "grid tied" is defined by simply plugging a typical AC power cord into your household AC socket, and somehow this will feed electricity back to the grid??

I did some research on eBay and saw that these GT inverters are not UL certified either... not to mention they are quite cheap, so I have doubts whether it'll even work. Any thoughts?

Here are some examples-
http://cgi.ebay.com/NEW-300-WATT-GRID-TIE-INVERTER-14-28VDC-110-VAC-/220745392045?pt=LH_DefaultDomain_0&hash=item3365735fad
http://cgi.ebay.com/350W-Grid-Tie-Inverter-Solar-Panel-14V-28V-DC-CA-/280656205465?pt=LH_DefaultDomain_2&hash=item415869d699
http://cgi.ebay.com/600W-GRID-TIE-INVERTER-12V-DC-110V-AC-INVERTER-600W-/250801401322?pt=LH_DefaultDomain_0&hash=item3a64edadea

Thanks,
-Rama

[niel]

until the federal government for this country, or any other country for that matter, makes it illegal for these inverters to be sold then they are free to sell to an unsuspecting public that it is illegal for them to use them as they are meant to be used. to sum this up is that it is not illegal to sell or own such inverters, but to use it as it is intended is. that is because they can bypass safety factors and other safety parameters that can make these gt inverters dangerous to use by simply plugging them into the wall.

[BB.]

Oh... They can work. They may even work well...

Just not safe per code.

-Bill

[dgsloan]

You will find that in the end they are not as cheap as you think. By the time you buy all the connectors and remote breakers and spare parts etc you will find that it is actually much cheaper to buy an enphase converter (for comparison only) - If you really want to plug it in = even though it is not safe - take an enphase and plug it into a dryer or stove outlet - I have heard of this being done to test out the electronics until a proper underground cable was installed. The other problem with the Power Jack is that they fail quite regularily. If you search on the internet you will find lots of different fixes (failures) and even eBay sites that sell parts for them. Their rating is way over specified - a 300watt inverter will only handle 175watts continuous.

[oil pan 4]

Saying they work well is giving them way too much credit.
They like to over heat and shut down. They are noisy.
In factory configuration a 300w unit might be able to run at 100 watts for extended time with out problem.
There are not really any saftys on them.
To make them use able you have to install a much larger fan, a breaker or fuse on the high voltage side, a push button power isolation relay and an over volt disconnect to get you started.
Unless you have a collection of these items just sitting around, you might want to go with the higher end inverters.

[SteveK]

Yep they work but not very well. A side by side with the SUN-500g model of these gorilla GTI's and a set of Enphase's show 20% production gain from the Enphases. This is using the best of the breed (SUN) and not Power Jack too. PJ is the worst of them.

We used a pair of Sun's for about a month last year. They do work but not very well. Had a hard time leaving the home in fear of fire. The Sun's will put out 72% efficiency but the power factor is pretty low ~ .7 until they are well loaded.

Still have the pair, never wil use them again.

[oil pan 4]

That is why to put them out side, away from your house.

[solar_dave]

That is why to put them out side, away from your house.

In the garbage can! ;)

[russ]

Ask the neighbor - maybe he will let you install them in his garage. Might not be too happy if it burns down but then---

[silvertop]

I dinked with a Power Jack, but to be honest when I have excess power ,Ill just run my inverter for my refrig. I dont think I would leave the house with the Power jack running for fear of fire....

[SteveK]

Heh, I like it.

So, talk the neighbors into letting me install them in the garbage pail in their garage then? Well, it beats the pants off of selling them to some unsuspecting ebayer and wondering if I burned their house down. This way I'll know for sure if I did.....

[XRinger]

The outside shell seems to be constructed much like the 12v automotive type
inverters that have been around for many years. It's 95% enclosed in aluminum.
Not like the PJs are made out of pine wood, soaked in fuel oil..

What's going to burn with any large amount of fire??
1200w PJ GTI
http://i46.photobucket.com/albums/f147/Xringer/Solar/n009.jpg

I've heard the FETs burn out and you might get a blown fuse,
but these PJs look like they are made like a lot of other inverters..

2.5kw (5kw peak) Stackable 48vdc - 120vac inverter.
http://i46.photobucket.com/albums/f147/Xringer/Solar/8tranformers.jpg
I think this one got up to about 72F when tested with a 1500w space heater.

All of four Chinese inverters I've looked at, (I have 2 more smaller 12v units)
all seem to have fuses on the DC input and AC output.

I've seen boards in PCs and PC power supplies go bad, but I've never
actually seen any make smoke and flames for more than a few seconds..

[solar_dave]

I don't think it was an issue with the unit burning but using a plug in to existing 15 AMP house circuit and overloading the line between the PJ and the circuit break in the panel.

[SteveK]

I don't think it was an issue with the unit burning but using a plug in to existing 15 AMP house circuit and overloading the line between the PJ and the circuit break in the panel.

That and, insurance problems, no UL, illegal to use, being charged for what you produce just to name a few.

I'd go on a limb and say that anyone installing them in their home is being a tad bit "shady" and underground about things. You know...like that rush that came from smoking in the boysroom in high school. That's how I felt anyways....

[XRinger]

I don't think it was an issue with the unit burning but using a plug in to existing 15 AMP house circuit and overloading the line between the PJ and the circuit break in the panel.

Humm, I guess if you exceeded the rating and the safety margin of your home's branch circuit.
15a * 120v = 1800w.. I guess mine is okay, since it's 1200w max. :roll:

I saw a Youtube of a guy (I think in Europe) using a bunch of PJs.
He had one connected to each of his panels. Maybe 15 or 20 panels.?.
He was getting pretty good results out of his system.
I'll bet he didn't have them all plugged into the same branch circuit.

The reason I got this 1200w PJ was to see if I could connect it to
a PWM or pure-sine-wave inverter and get it to sync up and work.
Wanted to see if it could be done. I was also wondering if it would
be possible to use the 1200w PJ with my gasoline generator.

If the PJ & 500w-800w of PV contributed power to the load connected
to the generator, perhaps the PV could help save gasoline during a long power failure..?.
Maybe the PJ would allow the generator to run at idle,
while the PV fed the basic house 300-600w load.?.

[XRinger]

That and, insurance problems, no UL, illegal to use, being charged for what you produce just to name a few.

I'd go on a limb and say that anyone installing them in their home is being a tad bit "shady" and underground about things. You know...like that rush that came from smoking in the boysroom in high school. That's how I felt anyways....


I think that a lot of the guys who buy PJs are hackers or Hams etc..
It's just another toy. I would not use one because of the insurance issue.
But, I will play around with mine outdoors.. (someday).
Maybe like this.. http://youtu.be/ESvL-Nc-pRk

[SteveK]

Xringer I've recently begun remodeling our 60 year old and have pulled the covers off the outlets in several rooms. What I found in there was more belly button lint and dust that appeared to be a great tinder box. Upon further inspection I found that the wire nut juntions (untaped) contained so much oxidation it was hard to tell if it would even conduct.

I looked into this and found this was a source of ignition in many house fires. I would imagine that the increased resistance at that point would create heat and sparks that Bear Grylls would be proud of.

This in an otherwise fully code-compliant home.

[XRinger]

Xringer I've recently begun remodeling our 60 year old and have pulled the covers off the outlets in several rooms. What I found in there was more belly button lint and dust that appeared to be a great tinder box. Upon further inspection I found that the wire nut junctions (untaped) contained so much oxidation it was hard to tell if it would even conduct.

I looked into this and found this was a source of ignition in many house fires. I would imagine that the increased resistance at that point would create heat and sparks that Bear Grylls would be proud of.

This in an otherwise fully code-compliant home.

My home was assembled in 1956, so I've replaced all the ungrounded outlets over the years.
And we had the service upgraded and added a breaker box (glass fuses gone! :grr )

The existing wiring still looks good. No squirrels have been at it yet..
All the runs seem to be end-to-end without any patches.
They used the outlet screws to daisy-chain to the next connection.
I don't know if they used any wire nuts. I've added some over the years.

Here in Woburn, the inspectors allows requesting homeowners to do their own work,
if it's not too complicated. (like changing the cable from the meter etc).
So far, all my work has passed inspection.

The cables in the attic are exposed to a lot of heat during the summer.
That's a bit worrisome. And now, they are buried deep under FG insulation.
I just hope the rodents don't dig them up and find them tasty..
I have fire sensors up there. I hope they never get used..

[BB.]

And then there where the aluminum wired homes and buildings (http://www.inspectapedia.com/aluminum/aluminum.htm) of the late 60's and early 70's...

About the only practical repair method I have seen is the Alumiconn connector (http://www.alcopstore.com/order/)... Basically a small bus bar setup to connect both aluminum and copper wiring together (hopefully) safely.

They probably are even better than wire nuts for copper to copper connections--but there is only one size and they are not cheap.

-Bill

[SteveK]

Seems once you start digging it is to no end. Every outlet box has a length of wire added to extend from a mass of wires in a wire nut. Everything is highly daisy chained for lack of a better term. The only way to connect the outlet itself is to add a single conductor in order to keep the other circuits complete.

So when I looked at this I couldn't help but think fire hazard. By adding the ChiTie inverter I felt it to be even more dangerous unless you ran a direct line from the breaker panel dedicated to it. Just the opposite intention of the unit itself. They claim plug and play, I see it as plug and possibly pay for it in loss of property. Or hire an electrician in many cases to provide for it.

[XRinger]

I'm running my PC and a few other loads off an inverter (MSW) right now,

http://i46.photobucket.com/albums/f147/Xringer/Solar/panel.jpg

I'm trying to do it as safely as possible. Just about everything is UL
approved parts and should be to code.. (or close :p)..

That little black box on the left side of the pic is a TED transmitter.
It's UL listed, but it's little power supply is likely more of a risk
than anything else I've got hanging off my wiring..

[solar_dave]

I think this has been covered pretty extensively before. if you place six 5 amp load on a #14 gauge line which is electrical code for 15 amps it is possible the breaker in the power panel will not trip if a plug in Inverter rated at 15 amps is added at the end of the line. This is way over the capacity of a 15 amp line, yet the 15 amp breaker in the panel will not trip because the source of power is from 2 locations, 15 amps from the breaker and 15 amps from the inverter. The aggregate power sources are well over the line rating.

This is certainly a huge fire risk on the 14 gauge wire, and I can't see how any of these plug in inverters would pass UL listings.

[XRinger]

I think this has been covered pretty extensively before. if you place six 5 amp load on a #14 gauge line which is electrical code for 15 amps it is possible the breaker in the power panel will not trip if a plug in Inverter rated at 15 amps is added at the end of the line. This is way over the capacity of a 15 amp line, yet the 15 amp breaker in the panel will not trip because the source of power is from 2 locations, 15 amps from the breaker and 15 amps from the inverter. The aggregate power sources are well over the line rating.

This is certainly a huge fire risk on the 14 gauge wire, and I can't see how any of these plug in inverters would pass UL listings.

Wouldn't that 3.6kw (30A) load (six 5A loads) trip the 15A breaker the second the clouds showed up? :D

I can see the danger you are pointing out. I can imagine there are people
out there, that would plug in a dozen 300w PJs on extension cords,
and then start adding waffle irons.

You are right, there is no way this type of device is ever going to be deemed safe.


A smarter design would be an island inverter that didn't put anything on the grid,
but could switch the load back to the grid. (when it got dark out).
A bit like the UPS Power Backup units people use on their PCs, but with solar PV charging the batteries.
http://2.imimg.com/data2/RW/WI/MY-/solar-ups-system-250x250.jpg

Have to make it look cute.. And smaller than this thing! :roll:
Or this one.. http://i46.photobucket.com/albums/f147/Xringer/Solar/z203.jpg

[TheBackRoads]

This guy likes his Power Jacks!


http://www.youtube.com/watch?v=t3Yi5tohQfU&NR=1

hehehe

JP

[solar_dave]

scary, he doesn't show the AC side of all that. Hope he doesn't live next to me!

[XRinger]

He's in the UK..

http://www.youtube.com/user/1R7E7B

[TheBackRoads]

I should have known from the music in the videos :p



TBR

[XRinger]

I should have known from the music in the videos :p



TBR

More PJs.. Check out this music..

http://youtu.be/f2BTNJQNUnk

Name that country! :p

[solar_dave]

one big plug strip????? oh so scary! 1.4Kw into that plug strip has to be not up to even the local code, but who knows about those overseas folks.

[XRinger]

I'm thinking that's a pretty large strip, so it might actually be rated for higher power, then our USA strips are rated for (1800w?).

The switching and monitoring work isn't bad. I'll bet these guys are running
a dedicated 220ac line into their home's breaker panels..
A line with no load outlets on it.

[stephendv]

Most multi-plug strips are 13A, so at 230V that's 2990W.

[TheBackRoads]

More PJs.. Check out this music..

http://youtu.be/f2BTNJQNUnk

Name that country! :p


hahhaa I was gonna say the UK and....... BINGO! lol :p

[XRinger]

Most multi-plug strips are 13A, so at 230V that's 2990W.

Only a kilowatt more than USA strips. :blush:
But still, those multi-PJ installations probably have their on cable running back to the breaker box.
Just like you would want, if you had a 230v 5kw gasoline back-up generator.

http://i46.photobucket.com/albums/f147/Xringer/Green%20slot/generator.jpg
Have never used mine.. Yet.. :cool:

[russ]

They claim the inspectors are tough there from what I have seen on other sites.

That wouldn't get by the janitor would it?

Panels flat on and close to the roof -

Looks like ____ engineering at it's best - you can fill in the blank with whatever ethnic slur first comes to mind.

Russ

[XRinger]

They claim the inspectors are tough there from what I have seen on other sites.

That wouldn't get by the janitor would it?

Panels flat on and close to the roof -

Looks like ____ engineering at it's best - you can fill in the blank with whatever ethnic slur first comes to mind.

Russ

Looks like he put the panels on the flat roof of a garage.

http://solarhope.co.uk/Solar%20PV/Solar%20PV.htm

http://solarhope.co.uk/Solar%20PV/18%20Solar%20Panel%20on%20Roof.jpg
Must be a real pain when it snows..


And, it looks like he had some hotwater collectors up there a few years ago.(2007 & 2008 ).

http://solarhope.co.uk/Solar%20Hot%20Water/Solar%20Hot%20Water.htm

He has also done an EV conversion (in 1992).. Seems like he's an experimenter.. :cool:

[TheBackRoads]

I wish I had that kind of money to spend on cool projects.....

[mkennedy]

Trust me when I say this, the powerjack grid tie inverters are useless and a scam. It goes with that old saying when its to good to be true it normally is. I know this because I purchased (5) 1200 w units and within the first 30 days (3) of them stopped working. I have tried numerous times to get a hold of the company to get this problem resolved and get my system back up and running but no one will contact me back. When I purchased the inverters they said it came with a 2 year warranty which is completly false because I have no way other than email (which they dont answer) to contact them. Save your money and by something from the USA so that when you do have an issue with the unit you will at least be able to contact someone.

[XRinger]

I've had a few Ebay Email exchanges with the PJ dealers,
it was a very frustrating experience. They sent me a
model that I didn't order (or want), and tried to convince
me it was better than the model I had ordered.
It took months to get them to take back the LCD 1200w PJ and send me a new unit.
But, it was all a waste of time, since they just took one
of their same LCD units and took out the LCD and mailed the unit to me.
They never got the order right and I finally gave up.

Months later, when I placed a bid on a cheap PJ product, my bid was rejected,
because I'm now banned from buying from their product line! :p

Anyways, I purchased my PJ for some experiments, to see if it was
possible to use them off-the-grid (with a non-grid AC source).

If I wanted to install a grid-tie system, it would be completely legal and safe
as I could make it. I think Enphase would be my GTI of choice.

Cheers,
Rich

[SolarGoth]

I've tested one of these awful little things. My observations:

1) It never worked. The unit just shines a brilliant red LED "FAULT" light. :p

2) The DC side wiring, on easily touchable binding post connectors, appears to not be isolated from AC line!

3) The inverter's internal components are totally janky. The inductor used in the voltage converter section is wound with suspiciously thin wire, there's no way this thing could have actually been pushing its rated 300 watts.

4) There are typos on the silkscreen on the PCB.

5) I begged my coworker to please take it home and get it out of my sight forever.

[XRinger]

I've tested one of these awful little things. My observations:

1) It never worked. The unit just shines a brilliant red LED "FAULT" light. :p

2) The DC side wiring, on easily touchable binding post connectors, appears to not be isolated from AC line!

3) The inverter's internal components are totally janky. The inductor used in the voltage converter section is wound with suspiciously thin wire, there's no way this thing could have actually been pushing its rated 300 watts.

4) There are typos on the silkscreen on the PCB.

5) I begged my coworker to please take it home and get it out of my sight forever.

1. That's very common, when there is no PV connected, or the PV voltage is out of range.
Did your coworker say, "It was working fine for months, until the smoke came out"? ;)

2. Not isolated from the AC line? That's wild! Was it both sides of the AC wired to the DC terminals? Or was it just one side of the line?

3. Everything is underrated, but transformer failure does not seem to be a (reported) problem. It's mostly the FETs that burn out.

4. Yeah, the manuals have typos too. You do realize that good English spelling is a problem when you're using a Chinese language computer? :D
(No English Spell-Check).


I have seen crazy AC grounding on a few Chinese made inverters.
But, I've checked out 4 different models and none had the DC shorted to AC.
That does seem like a transformer wiring problem..
Where the primary is shorted to the secondary.

There is a new breed of GTI (HERIC-topology) that does not use transformers..
http://www2.electronicproducts.com/Optimizing_photovoltaic_systems-article-fapo_Avnet_apr2010-html.aspx

http://www.solarnovus.com/index.php?option=com_content&view=article&id=2886

Seems like that's gona be a UL problem..

[Renewable Ray]

Trust me when I say this, the powerjack grid tie inverters are useless and a scam. It goes with that old saying when its to good to be true it normally is. I know this because I purchased (5) 1200 w units and within the first 30 days (3) of them stopped working. I have tried numerous times to get a hold of the company to get this problem resolved and get my system back up and running but no one will contact me back. When I purchased the inverters they said it came with a 2 year warranty which is completly false because I have no way other than email (which they dont answer) to contact them. Save your money and by something from the USA so that when you do have an issue with the unit you will at least be able to contact someone.


OK, so I read a lot about these cheapy grid tie inverters like the Power Jacks. But I am dying to know what US built units have people bought and had good luck with?

[MiamiSunrise]

1. That's very common, when there is no PV connected, or the PV voltage is out of range.
Did your coworker say, "It was working fine for months, until the smoke came out"? ;)

2. Not isolated from the AC line? That's wild! Was it both sides of the AC wired to the DC terminals? Or was it just one side of the line?



It worked for about three days, then started getting really intermittent on him. I'm sure the PV input voltage was in range, the thing just wouldn't wake up. Tiny red LED nightlight. 8)

As for the lack of isolation, there was solid continuity between AC neutral, chassis, and the DC side, with an open ground. Not entirely unlike the old StatPower and Xantrex (after buying StatPower) mobile inverters where the AC outlet ground prong went to nothing inside. Of course, guess what inverter design the Chinese copied en masse... BLEH!

[computerpc101]

I would like to update on Power jack GTI, I though that it should improve.

I bought 2 PJ 600W ver3.3, I opened its case, It looked better inside, All parts was solder fine and no lose heatsink mounting, All coils are glued.

I tested it with 200W solar panel, It worked well with one panel, However, After 1 week, One GTI stop working, AC side MosFET Q8 burn out, it is still not fix this problem yet.

Stay away from Power jack GTI.

[computerpc101]

I would like to update on Power jack 600W GTI that it burn out, I was testing my Ver 3.3 PJ600W version 3.3 dated Jan/2012, I find the problem that why it burn out, It has a Big red tag on power cord to remind me but I didn't pay attention to it, it was my fault, You have to remove DC first before AC. It was burned out because I plug/uplug power and Toggle AC swith while DC still connecting.

I replaced AC MosFET Q8, It works fine again, I load it with 450W testing for all day long without problem.

When I emailed to my Ebay's dealer, They seemed to care very much, I told them I fixed it, Anyway, They send me a free New one as replacement.

Once Replacement come, It looks slightly different, It is Power Jack 600W Ver 3.4 dated March 2012
It is upgrade then Ver3.3 as below, Better AC switch with reset button build in, Better power cord, Higher Power DC side MosFET , it should be no problem to handle 600W while Older version seem underrated power.

I paid $129 for my Ver 3.3, now they are selling the new one ver 3.4 for $148, I guess that you paid what you get.

China has Fit program now, Some building come with solar panels, There are market, That's why Power jack improves their products for better quality.

Anyway, Bigger problem is that it doesn't really come with a good User Manual, UL, Etc.

[solar_dave]

Removing the AC blew it up? Sounds like junk, what happens if it is running and the utility bumps the power? POOF? That is just ugly.


Hopefully you do know that in the USA plug in inverters are illegal.

[computerpc101]

If I buy a 1kW to 3KW system, I will buy Enphase GTI system, Made in USA, inexpensive, and it works well on cloudy day as well as Sunny day with highest overall efficiency.
If I buy a 3KW and Up system, I will go for String high voltage GTI.

Power jack GTI just fit low budget low power GTI system, My buddy has low price SWEA? GTI few year back, It was the worse GTI I ever seen, If there are other good inexpensive USA made good GTI similar, Power jack will be gone.

If you plug/unplug AC line while GTI pumping DC power, It will have very high surge voltage while MPU take time to detect this loading situation, If you do it many times, Even good GTI will burn out, That's why most of them hardwired to 220V power box not allowing fooling around.

I am glad that I didn't start a big project using those expensive Legal High power inverter because nobody will buy those GTI here, With Small price of power jack, I am able to test and measure real world daily production of solar power, It takes 40+ years to pay back, I will wait for incentive in my area with Fit program with detail power company requirement for a legal system.

My buddy and me, We both Laborer making small income, 2 years ago, He told me that he can get legalize marijuana grower license by paying $500 doctor, He did it and in short time, not sure how much money he made, he bought a new house 2 million dollars paying by cash, few months ago, I saw him on news, He was shot to dead on street.

My other Germery buddy, due to high gas price, we made a wine distiller using copper pipes, by using rotten fruits plus 10 day, we made almost free drinking Alcohol which we can mix 15% in gas to save up money, However, He drank too much of it and stroke and end up staying hospital for 3 months, Now we know that wine distiller is illegal worldwide.

Sorry for off topic, I am just confuse in life about legal and ill-legal as much as some State in USA allowing high power gun weapons for sale.

[BB.]

Yea, with the marijuana laws, there can be a lot of money made, at high risk, trying the thread the legal system(s) in states like California (where I live).

In any case, since we are a forum sponsored (i.e., hosting fees and system administration paid for) by Northern Arizona Wind & Sun--We try to avoid "non-solar" politics and keep the discussions focused on the practical side conservation and renewable energy (which is hard for me too--I really do enjoy a friendly political discussion with people who have different ideas than mine8)).

-Bill

[jagec]

My other Germery buddy, due to high gas price, we made a wine distiller using copper pipes, by using rotten fruits plus 10 day, we made almost free drinking Alcohol which we can mix 15% in gas to save up money, However, He drank too much of it and stroke and end up staying hospital for 3 months, Now we know that wine distiller is illegal worldwide.

Sorry for off topic, I am just confuse in life about legal and ill-legal as much as some State in USA allowing high power gun weapons for sale.

That's why I stick to brewing beer...legal most everywhere except for the Middle East, pretty simple equipment-wise, and no chances of poisoning yourself. Of course, you can't burn it in your car.

I believe that making bio-diesel is legal in the US. Not sure about (fuel-grade) ethanol.

And I think that people from both extremes of the political spectrum can agree that the US legal system is dysfunctional, banning fairly innocent things in the name of public welfare while allowing much more potentially dangerous things in the name of individual freedom.

[niel]

i don't think i have to say that this has veered too far off the subject and, even though i agree with what's said, it is starting to go political.

[Sparkletron]

Here's one (http://www.amazon.com/gp/product/B005N29SGM/ref=ox_sc_act_title_1?ie=UTF8&m=A1H80H5UHTLXX) I reviewed on Amazon. It has a higher max input (52VDC) compared to the ones I've seen on ebay, which are typically around 30VDC regardless of the wattage rating.

[icarus]

Do we have to go down this road AGAIN?

Tony

[Sparkletron]

I'm sorry--did I do something wrong?

[Cariboocoot]

Do we have to go down this road AGAIN?

Tony

Maybe we could just carve some of the dicta into stone and place them in a conspicuous place on the forum? :roll:

[icarus]

I'm sorry--did I do something wrong?

You didn't do anything wrong per we,, it is just that we don't encourage (in your own words on you amazon review) illegal, non code approved installtion. We have had threads ad infinitum regarding power jack and other non UL listed (illegal) grid tie inverters.

Tony

[Sparkletron]

Please don't construe my post as either encouraging or discouraging the use of these devices. I'm simply providing information on a class of products--SGPVs--that is increasingly gaining interest among solar hobbyists. I certainly don't believe we should ignore this interest, or that we should censor all discussion of these devices and reflexively bash them and say things that aren't true. People are going to get information one way or another; better they get it here from an established and authoritative forum.

The fact is that if these products didn't work, no one would be interested in them, and the market would vanquish them without any help from us. But they do work and they're by far cheaper and easier to implement than anything else on the market. Indeed, SGPVs don't really belong in the "hype and scam" forum because they're neither. Granted they're illegal to use in the USA. But even here, efforts are being made (http://www.scientificamerican.com/article.cfm?id=solar-power-in-a-box-sunfish) to legitimize this technology. Like it or not, there's a growing market for SGPVs, and they'll continue to evolve and improve over time. My post demonstrates such improvements: new safety features and higher max input voltage. In this way, I feel that my post contributes to the discussion without crossing any liability lines. These are just my opinions; as moddies you make the rules and can do what you wish.

[Cariboocoot]

Work they do. Legal they should never be. The reason being the method of install.

Once again: the problem is that any quantity of these may be plugged in to a non-dedicated circuit leading to the potential of putting more current on wiring inside your walls than it can handle.

Because of this there is no way to eliminate the safety concerns of these products. They just make it too easy for people to add a potential fire hazard to their home.

[Sparkletron]

Your concerns are certainly legitimate. Yet this is an international forum; what the USA feels is too dangerous may be considered an acceptable risk elsewhere given proper safeguards. As with many products that we use, this one is not without risk, and must be used properly, responsibly, and in accordance with law.

I am curious why you believe that the safety features built into this device (fuses, thermistors, etc.) would do nothing to stop overcurrent. Let's say someone were to feed ten of these into a single 15A branch, each contributing about 4 amps--not to mention the amps coming from the grid. Why do you believe this would absolutely result in disaster?

[solar_dave]

Your concerns are certainly legitimate. Yet this is an international forum; what the USA feels is too dangerous may be considered an acceptable risk elsewhere given proper safeguards. As with many products that we use, this one is not without risk, and must be used properly, responsibly, and in accordance with law.

I am curious why you believe that the safety features built into this device (fuses, thermistors, etc.) would do nothing to stop overcurrent. Let's say someone were to feed ten of these into a single 15A branch, each contributing about 4 amps--not to mention the amps coming from the grid. Why do you believe this would absolutely result in disaster?

OK so you have 4 of these on a line, now you plug in 25 amps of load on the line, the 15 amp mains breaker will not trip as the power is sourced from 2 locations now (15 amps from the mains and whatever from the 4 plugins 16 amps?) but certainly the 14 gauge wire is overloaded.

I would hope the mains breaker would trip if someone tried to hook 10 of these on a 15 amp line but with any loads also on the line as they ramp up the output it too could cause a heating event on the 14 gauge house wire. Hopefully the homeowner would not do something stupid like swap the mains breaker for a larger one.

[Cariboocoot]

Your concerns are certainly legitimate. Yet this is an international forum; what the USA feels is too dangerous may be considered an acceptable risk elsewhere given proper safeguards. As with many products that we use, this one is not without risk, and must be used properly, responsibly, and in accordance with law.

Not really a matter of law so much as of physics.


I am curious why you believe that the safety features built into this device (fuses, thermistors, etc.) would do nothing to stop overcurrent. Let's say someone were to feed ten of these into a single 15A branch, each contributing about 4 amps--not to mention the amps coming from the grid. Why do you believe this would absolutely result in disaster?

The problem is not the current coming from the micro-inverter, it's the potential total current on the wire. If there is only the inverter on the line, it is safe. But here is a likely scenario which is the basis for the concerns:

You have a 15 Amp duplex outlet that is convenient to the inverter. Why stop at one? Use a power bar and plug in several of them, totally 600 Watts. No worries as that's only 10 Amps and the 14 AWG wire in the wall can handle that. Providing nothing else is plugged in to the same circuit, it is "dedicated" to conducting current from the inverters to the breaker panel.

Now most wiring has more than one outlet on it. Plug something into another outlet on the same circuit. As long as that draw is no more than 10 Amps everything is still fine, as regardless of the power source it will still only be 10 Amps on the wire.

But should the load on the wire exceed the wiring's limit of 20 Amps ... you have 15 Amps available from the breaker box and another 10 from the inverters. That's 25 Amps that can flow on wire designed not to exceed 20. No circuit protection on either end will trip; the wire will overheat and ignite.

Don't think this is unlikely to happen. One of the attractions of the plug-n-play is the ease of expandability, and it is likely that panels/inverters/plugs will all be located in the same spot and connect to the same circuit.

Did I mention the problem with unregistered GT systems causing some meters to spin forward instead of backward should production reach a surplus?

On the whole, this is equipment whose potential faults can not be avoided by any reasonable measure.

[Sparkletron]

To use my example, when ten SGPVs produce 40 amps of current on a branch designed for 15 amps max, I agree that an overcurrent condition exists. And when that happens, each fuse in each SGPV blows, removing the source of the overcurrent. It would be pointless for the grid breaker to trip since this would do nothing to address the source of the overcurrent--which is not the grid but the ten SGPVs. Are you saying that the fuses in the SGPVs will not blow? Or that they won't blow fast enough? Or that even if they blow, the overcurrent condition will remain?

[solar_dave]

To use my example, when ten SGPVs produce 40 amps of current on a branch designed for 15 amps max, I agree that an overcurrent condition exists. And when that happens, each fuse in each SGPV blows, removing the source of the overcurrent. It would be pointless for the grid breaker to trip since this would do nothing to address the source of the overcurrent--which is not the grid but the ten SGPVs. Are you saying that the fuses in the SGPVs will not blow? Or that they won't blow fast enough? Or that even if they blow, the overcurrent condition will remain?

How are each of the individual devices going to see the over current, all they know about is there internal amps out. The fuses will not trip in the devices but the mains most likely will once the the 10 devices in combination achieve 15 amps backfeed. The problem lies with non dedicated back feed, proper wire sizing, Grid tie interconnect agreements (which require UL approved devices) , permits to change your electric service( which in general are to NEC code), proper meters to detect the amount of back feed, etc, etc,

Edit:
BTW Burn your house down with one of these setups and try and collect from your insurance company.

[Cariboocoot]

To use my example, when ten SGPVs produce 40 amps of current on a branch designed for 15 amps max, I agree that an overcurrent condition exists. And when that happens, each fuse in each SGPV blows, removing the source of the overcurrent. It would be pointless for the grid breaker to trip since this would do nothing to address the source of the overcurrent--which is not the grid but the ten SGPVs. Are you saying that the fuses in the SGPVs will not blow? Or that they won't blow fast enough? Or that even if they blow, the overcurrent condition will remain?

No, it doesn't work like that.
Each SGPV sees only its own peak output, not the total current flowing through the wire. There's no way they can sense that in and of themselves.

Essentially you'd be powering the one wire from several different sources. Each source (including the main breaker panel) protects the wire against exceeding the individual source peak current, but there is absolutely no circuit protection on the total current in the wire.

[Sparkletron]

Not really a matter of law so much as of physics.

Oh there's quite a bit of law (politics) involved in electrical codes. For example, most homes do not have adequate grounding or protection from lightning, because such protection is immensely expensive. But we have something better than physics--we have actuarial tables. And so we perform the cost-to-benefit analysis and accept a certain amount of risk. But--again--what the USA considers an acceptable risk may differ from one locale to the next. Physics can give us the facts but it can't decide what an acceptable risk is.

[Sparkletron]

No, it doesn't work like that.
Each SGPV sees only its own peak output, not the total current flowing through the wire. There's no way they can sense that in and of themselves.

That's interesting, because these devices will not work unless they sense existing power on the line. That's one of the safety features. So you're saying that the SGPV can detect existing power on the line, but cannot know anything about the nature of this power? Neither the amps nor volts? How is this possible?

[solar_dave]

Oh there's quite a bit of law (politics) involved in electrical codes. For example, most homes do not have adequate grounding or protection from lightning, because such protection is immensely expensive. But we have something better than physics--we have actuarial tables. And so we perform the cost-to-benefit analysis and accept a certain amount of risk. But--again--what the USA considers an acceptable risk may differ from one locale to the next. Physics can give us the facts but it can't decide what an acceptable risk is.


And the physics are with 4 of these devices plugged in (16amps) and attached to a 15 amp house run mains breaker the possibility exists to have 31 amps of potential power on a 14 gauge wire which will burn if a large load is also placed on the line and no breakers or fuses will trip. It is as simple as that. Being non dedicated can cause a catastrophic wire failure. This is why there is NEC code for adding solar to your house. It is to protect you and your life & loved ones and your possessions.

I am not saying these device can not be made safe if done properly, they probably can if one designs the backfeed system with proper code in mind. But you will play hell to get the utility and the local permitting agency to buy off on it.

[solar_dave]

That's interesting, because these devices will not work unless they sense existing power on the line. That's one of the safety features. So you're saying that the SGPV can detect existing power on the line, but cannot know anything about the nature of this power? Neither the amps nor volts? How is this possible?



Generally they detect volts and line frequency, but they can know nothing about the loads (amps) placed on the line. How could they? the loads do not run through the device.

[Cariboocoot]

That's interesting, because these devices will not work unless they sense existing power on the line. That's one of the safety features. So you're saying that the SGPV can detect existing power on the line, but cannot know anything about the nature of this power? Neither the amps nor volts? How is this possible?

All grid tie systems shut down if they detect no AC power or power outside of acceptable parameters (too low, too high, wrong frequency). This is anti-islanding and prevents them from energizing the neighborhood in the event of an outage.

To each of these units the over-loaded wire would appear as correct for Voltage, maximum current, and frequency. They would not shut down. The only part of the circuit that will "see" something is wrong is the over-loaded 14 AWG right before it fries.

[Sparkletron]

To each of these units the over-loaded wire would appear as correct for Voltage, maximum current, and frequency. They would not shut down.

My understanding is that when a current is traveling along a wire and encounters a branch, the current divides evenly. If you have ten SGPVs all contributing current, each stream should divide upon encountering various branches--including the feed lines of all the other SGPVs. Since there are eleven branches (one for each SGVP plus the house branch), each SGPV's stream should encounter ten branches and contribute .4 amps to each branch. But since we have ten SGPVs all doing the same thing, then each branch ends up with 10 * .4 = 40 amps.

Now if my understanding of what you're saying is correct, then I'm wrong, and each branch, upon encountering ten other branches (nine SGPV branches plus the house branch), doesn't divide it's current evenly, but instead contributes all of its current to the house branch and ignores all the other branches. Can you explain a bit more how this selective process works?

[Cariboocoot]

My understanding is that when a current is traveling along a wire and encounters a branch, the current divides evenly. If you have ten SGPVs all contributing current, each stream should divide upon encountering various branches--including the feed lines of all the other SGPVs. Since there are eleven branches (one for each SGVP plus the house branch), each SGPV's stream should encounter ten branches and contribute .4 amps to each branch. But since we have ten SGPVs all doing the same thing, then each branch ends up with 10 * .4 = 40 amps.

Now if my understanding of what you're saying is correct, then I'm wrong, and each branch, upon encountering ten other branches (nine SGPV branches plus the house branch), doesn't divide it's current evenly, but instead contributes all of its current to the house branch and ignores all the other branches. Can you explain a bit more how this selective process works?

Current only divides evenly if it branches to a parallel path. There is no parallel path here. There are several separate sources feeding into one wire. The current available from each source is limited to its maximum, but the current along the common wire can be the sum and total from all sources.

It's like having a whole lot of on-ramps to the freeway: lots of cars coming in from all directions. Each ramp has light traffic on it, but when they all get on the common corridor you get grid lock: too much traffic trying to drive down too little road.

Please don't take this the wrong way but your difficulty in understanding the problem is another problem with these plug-n-play devices: too many people assume that because it is sold and has a fuse in it it must be safe to use. so long as you don't do it wrong, it would be. But it's much too easy to do it wrong.

BTW, most of the houses that have inadequate wiring in any form do so because they were built before the code required the grounding, et cetera. Any house built to code these days will have adequate wiring, including grounds. But "built to code" is the key; you can cheat on any building code aspect - and thus make the house unsafe.

[Sparkletron]

I am not saying these device can not be made safe if done properly, they probably can if one designs the backfeed system with proper code in mind. But you will play hell to get the utility and the local permitting agency to buy off on it.

Exactly. And that's politics--not physics.

I honestly don't know the exact nature of the overcurrent protection on these devices, but you moddies seem absolutely certain that they won't work if you combine enough of them. I don't have multiple SGVPs upon which to test any of this, so I'm just thinking in terms of batteries and what happens when you add additional batteries. That is something I could test and measure on my end.

[Cariboocoot]

Exactly. And that's politics--not physics.

I honestly don't know the exact nature of the overcurrent protection on these devices, but you moddies seem absolutely certain that they won't work if you combine enough of them. I don't have multiple SGVPs upon which to test any of this, so I'm just thinking in terms of batteries and what happens when you add additional batteries. That is something I could test and measure on my end.

The problem isn't with the inverters themselves, it's with plugging enough of them into the same wire so that wire has the potential to be overloaded. Each inverter can only sense its own current, not the collective total. If the wire only feeds the breaker at the box (as with a dedicated GT circuit) then an excess output will trip that breaker before the wire is overloaded. When you're able to plug in as many current sources as you wish that will feed unknown loads between the inverters and the breaker connecting to the main grid you've got the potential for a problem.

[Sparkletron]

Current only divides evenly if it branches to a parallel path. There is no parallel path here.

So my house branch comes to a standard outlet. Let's say it has two sockets. You're telling me that each of those sockets is not connected to the house branch in parallel? Of course they are! And into each socket I plug in an SGVP. Now each SGVP is connected to the house branch in parallel. How could it be any other way? If the sockets of an outlet were connected in series, then neither socket would work unless they were both being used at the same time.


It's like having a whole lot of on-ramps to the freeway: lots of cars coming in from all directions. Each ramp has light traffic on it, but when they all get on the common corridor you get grid lock: too much traffic trying to drive down too little road.

I get the analogy. But electrons are not like cars eager to get on the freeway. They don't know which branch is the freeway. They encounter branches and divide--even if some of those branches are in fact "on-ramps" from other power sources.


Please don't take this the wrong way but your difficulty in understanding the problem is another problem with these plug-n-play devices: too many people assume that because it is sold and has a fuse in it it must be safe to use. so long as you don't do it wrong, it would be. But it's much too easy to do it wrong.

Believe me if I end up learning something it will make my day. And for what it's worth--I am listening and trying to give you moddies the benefit of the doubt.

[Sparkletron]

Each inverter can only sense its own current, not the collective total.

This is really the only point of contention. I understand all about wire gauges, overcurrent, etc. The only part of this I don't grasp is how all of the feed lines are not experiencing the exact same amperage as all the rest (including the house branch). Somehow, the current from all the SGVPs avoid every branch but the house branch. How? Maybe I need to see a diagram...

[Cariboocoot]

So my house branch comes to a standard outlet. Let's say it has two sockets. You're telling me that each of those sockets is not connected to the house branch in parallel? Of course they are! And into each socket I plug in an SGVP. Now each SGVP is connected to the house branch in parallel. How could it be any other way? If the sockets of an outlet were connected in series, then neither socket would work unless they were both being used at the same time.


Your separate inverters are not complete parallel circuits as with standard house wiring. They are individual circuits which interconnect at a common point; the potentially overloaded wiring.

If you have multiple charge controllers hooked up to the same battery bank, each controller and its wires only sees the current it is producing. If the connections are made to bus bars or other common connectors which then go to the battery, the wiring from the common point to the batteries sees the total from all charge controllers connected. Three controllers at 20 Amps each equals 60 Amps total going to the battery. But from the controller to the common point (on either polarity side) is still only 20 Amps. Only from the common points to the battery (on either polarity side) do you see the full 60 Amps. If each controller has a fuse capable of handling the 20 Amps the wiring from controller to common point is safe, but there is no circuit protection between the common point and the batteries.

With multiple plug-n-play inverters there is no circuit protection after the point where the sources come together. Thus it becomes possible to overload the wire after that point.

[Sparkletron]

Your separate inverters are not complete parallel circuits as with standard house wiring. They are individual circuits which interconnect at a common point.

OK let me see if I can grasp this. The reason the current from one SGPV can't flow into the feed line of another is because there's no path to complete the circuit, because these inverters are not electrical loads.

BTW, this means that charge controllers have the same issue, and all their overcurrent protections are for naught if not used properly.

[Cariboocoot]

OK let me see if I can grasp this. The reason the current from one SGPV can't flow into the feed line of another is because there's no path to complete the circuit, because these inverters are not electrical loads.

BTW, this means that charge controllers have the same issue, and all their overcurrent protections are for naught if not used properly.

Nope. Sorry. Still not right. The charge controller's circuit is through the battery and back the other side. But the only current it is "aware" of is what goes in and out of it specifically. Other controllers send their current through the common conductors (including battery) but not through the other controllers.

Let's try some word pictures:

Utility 15 Amp ==== OUTLET ==== OUTLET ==== OUTLET ==== OUTLET
Normal household circuit, right?

Utility 15 Amp ==== OUTLET ==== OUTLET ==== LOAD ==== OUTLET
Here we've added a load.

Utility 15 Amp ==== OUTLET ==== OUTLET ==== OUTLET ==== Inverters 10 Amp
Here we have the inverters back-feeding the utility.

Utility 15 Amp ==== OUTLET ==== OUTLET ==== LOAD ==== Inverters 10 Amp
Here the load can draw from both power sources. If it is 22 Amps theoretically 11 Amps will come from each source.

Utility 15 Amp ==== OUTLET ==== Inverters 10 Amp ==== OUTLET ==== LOAD 22 Amps
This one is the problem. Current from the utility to the Inverters can not exceed 15 Amps, but from that point to the LOAD it can. The power coming from the utility does not go through the Inverters, so they don't "know" about it.
Likewise the power coming from the inverters does not go through the Utility breaker. Thus from the point where the two power sources come together to where the LOAD is can be 22 Amps, but neither the circuit protection in the Utility box nor in the inverters sees this current.

[solar_dave]

Coot hit the nail on the head. This is why a dedicated back feed is required by code, it controls the amps traversing the wire. Also the size of the main panel buss bar must be considered for a similar reason.

Also an AC disconnect needs to be part of the circuit and usually a DC disconnect is also required before the inverters by code. These are there for fire department safety and be accessible from the outside of the house, clearly labeled.

[ggunn]

This is really the only point of contention. I understand all about wire gauges, overcurrent, etc. The only part of this I don't grasp is how all of the feed lines are not experiencing the exact same amperage as all the rest (including the house branch). Somehow, the current from all the SGVPs avoid every branch but the house branch. How? Maybe I need to see a diagram...
The problem is not the branch current(s) but the current in the, er, trunk, where they merge. Each unit monitors its own current but none of them can see the current in the conductors where they all come together. Nothing is monitoring that current when there is a load elsewhere on that circuit, so it is very possible (easy, even) to have an unprotected overcurrent situation with insulation melting and fires starting. You say that you "understand all about wire gauges, overcurrent, etc." With all due respect, I don't think that you do. The reason why "all of the feed lines are not experiencing the exact same amperage as all the rest (including the house branch)", which you admitted that you do not grasp, is that the "house branch" carries the sum of all the inverter currents plus whatever load demand may be presented to the circuit in excess of those currents, and no single OCPD sees that total current.

Code says that the total OCPD's feeding a conductor must not exceed 120% of the rated ampacity of that conductor. In this example, that is the sum of the breaker feeding the circuit from the service plus the sum of all the fuses or breakers in the renegade inverters plugged into that circuit. If the sum of all those exceeds 120% of the conductor's rating, then you are at risk of an overcurrent hot spot happening somewhere in that circuit. If it is a matter of law, then it's a good law, IMO. If it is an acceptable level of risk for you and you can get away with it, go for it, but if you start a fire your insurance company will (justifiably) deny the claim.

EDIT: Here's a simple example. Say you have a 15A service breaker feeding a two receptacle circuit with correspondingly rated conductors. In the receptacle closest to the service, you have a plug-in inverter rated/protected at 15A. In the other receptacle, you plug in a load that draws 30A. The house breaker doesn't have a problem; it only sees 15A. Neither does the inverter OCPD; it only sees 15A. But the conductors between the first and second receptacle are carrying 30A. Normally (without the inverter's contribution), the house breaker would trip and protect the conductors, but in this scenario you may have just burned your house down.

[Sparkletron]

Those diagrams are very helpful.

So even a single SGPV can create an uncontrollable overcurrent situation IF you locate it between the grid and the source (not at the end of a branch) and IF your load exceeds the max rated amps for the branch. And because of the difficulty in seeing through walls and knowing exactly which outlet is the last one on the branch, the average person is unlikely to implement the SGVP safely.

Still, assuming that the load is a major appliance (it's drawing a ton of amps after all), it would almost certainly have its own overcurrent protection...

GRID ===== OUTLET WITH INVERTER ===== OUTLET WITH LOAD

Wouldn't this merely result in the load's fuse blowing?

-S

[Cariboocoot]

Still, assuming that the load is a major appliance (it's drawing a ton of amps after all), it would almost certainly have its own overcurrent protection...



In 50 years I've yet to see a major appliance with its own over-current protection.
They put fuses in TV's, radios, stereos, computers ... all pretty light-weight stuff. But space heaters? Nah! What could go wrong there? :p

One thing that has bugged me for years is the lack of circuit protection in extension cords. Easiest thing there is to overload, and they are one of the top causes of electrical fires.

But even if the appliance did have protection, it would only be for its draw; not the total load on the household wiring. So again you have the same problem of being able to supply a section of wiring with more current than it is able to handle.

[Sparkletron]

Well certainly an appliance that needs 20 amps and expects to be on a 20-amp-rated branch will not have a problem when it detects 20 amps even if that represents an overcurrent for the branch. But if we're talking about following the rules, that 20 amp appliance is going to have a 20 amp NEMA plug, which is keyed and won't fit into a NEMA 15. Furthermore, the appliance's own overcurrent protection (even if it's merely a lowly fuse) will save the day in the event of a short-circuit.

[Cariboocoot]

Well certainly an appliance that needs 20 amps and expects to be on a 20-amp-rated branch will not have a problem when it detects 20 amps even if that represents an overcurrent for the branch. But if we're talking about following the rules, that 20 amp appliance is going to have a 20 amp NEMA plug, which is keyed and won't fit into a NEMA 15. Furthermore, the appliance's own overcurrent protection (even if it's merely a lowly fuse) will save the day in the event of a short-circuit.

That only applies if a failure in the appliance itself is the cause of the overload.
The problem we're looking at here is being able to put too much cumulative power source at one end of a wire and too much cumulative load at the other. Essentially "rewiring" the circuit so that it contains what are now inadequately sized conductors.

[jeffkruse]

Still, assuming that the load is a major appliance (it's drawing a ton of amps after all), it would almost certainly have its own overcurrent protection...

GRID ===== OUTLET WITH INVERTER ===== OUTLET WITH LOAD

Wouldn't this merely result in the load's fuse blowing?

-S

What if you plug in two loads, three loads, and decide to make toast? You generally don't know whats connected to the circut. Can you do it safely, sure, if you (and everyone in the house) understand what you are doing.+

[Sparkletron]

In my area, building code requires that all switched receptacles be installed upside down. It's very convenient. Perhaps something similar could be done for SGPVs. For example, if they were sold with a special keyed plug that won't fit any standard NEMA, and then an electrician is required to install the matching receptacle at the end of a branch...

GRID ===== OUTLET WITH LOAD ===== OUTLET WITH INVERTER

This would create the safe implementation that you were talking about. Of course it would raise costs (special plug, electrician), but it would still be considerably cheaper than what's involved with standard grid-tie.

[Cariboocoot]

Or in other words make sure the GT inverter is connected via a dedicated line, which is what the NEC says now.
The whole point and problem with plug-in inverters is that it makes it just too easy to screw up and burn your house down.
Not that there aren't a million ways for Joe I. Dunno to do that already. :p

[Sparkletron]

Well it wouldn't be a dedicated line because it would share the branch with the grid. The point is that these SGPVs are subkilowatt solutions. Too small for their own dedicated line. Too small for traditional grid-tie. Power companies would laugh if you wanted to grid-tie a 250W panel.

[ggunn]

Well it wouldn't be a dedicated line because it would share the branch with the grid. Which is precisely the problem. If your renegade inverter is running at full capacity, a load or combination of loads on the circuit it is plugged into has that capacity plus the full rating of the service breaker available before the breaker will trip. If that summed current exceeds the ampacity of the conductors, the service breaker can't protect them.

[solar_dave]

Which is precisely the problem. If your renegade inverter is running at full capacity, a load or combination of loads on the circuit has that capacity plus the full rating of the service breaker available before the breaker will trip. If that summed current exceeds the ampacity of the conductors, the service breaker can't protect them.

That is why they will never get a UL rating.

[solar_dave]

. Power companies would laugh if you wanted to grid-tie a 250W panel.

Not really, they are done all the time with Enphase micro-inverters and a proper dedicated to code install. It is just poor economics to do just one, where the costs to permit and added the proper disconnect equipment are involved as they should be.

[Sparkletron]

I distinctly recall reading that some power companies require at least 1 kilowatt. But the fact is I just called my own utility and they confirmed that there is no limit with them. In any case, it's a lengthy and expensive process and I agree makes no sense in the subkilo range.

I thought the point of micro-inverters was not to facilitate subkilo grid-tie, but to use many redundant inverters in lieu of one large inverter. That way if one panel goes offline, it doesn't bring down the entire system. Likewise, if one micro-inverter has trouble, the other inverters are still working. At the end of the day, the sum of all the micro-inverters is typically in kilowatts.

[solar_dave]

I distinctly recall reading that some power companies require at least 1 kilowatt. But the fact is I just called my own utility and they confirmed that there is no limit with them. In any case, it's a lengthy and expensive process and I agree makes no sense in the subkilo range.

I thought the point of micro-inverters was not to facilitate subkilo grid-tie, but to use many redundant inverters in lieu of one large inverter. That way if one panel goes offline, it doesn't bring down the entire system. Likewise, if one micro-inverter has trouble, the other inverters are still working. At the end of the day, the sum of all the micro-inverters is typically in kilowatts.

Yes all of that is true plus installs where shading is a problem, just the point was that each panel has its own inverter but all the installation requirements exist and the overall system install does much better with scale.

[solarvic]

Probably true but the powerjack inverters are illegal to use. If you want to grid tie why not use approved equipment. This powerjack and other similar junk keeps getting new victims that want to justify using them and will be sorry if thier power co finds one in use and shuts off the power or your house burns down. Everytime the moderators and people that know more than I do tell you not to use this non approved equipment you want to justify using it is ok. The YOU in previous sentence isn,t specifically addressed to you only but to all that want to be illegaly using unaproved equipment. As far as I know this forum doesn,t approve garilla electrical equipment but new people buying this type of equipment keep writing to the forum about it. :Dsolarvic:D

[Sparkletron]

People are interested in SGPV because it's a cheap simple plug-and-play subkilo solution. Most of the time it works without issue and does not result in disaster. Yes it's illegal to use in the USA and probably most modern industrial nations. I doubt it's illegal to use everywhere. Discussing it as we are doing makes people aware of the specific dangers. I certainly learned a lot and I'm grateful to the forum and moddies for patiently explaining things in more detail.

[ggunn]

Most of the time it works without issue and does not result in disaster. Would you fly on a plane that doesn't crash "most of the time"? :D

[Sparkletron]

Funny you should pick that analogy because that's exactly what Chuck Yeager did for a living. Oh wait. Actually, the planes he flew in did explode most of the time...

As I stated before, science can give us the facts, but it can't tell us what an acceptable risk is.

There are areas on the planet that don't have clean running water and flush toilets, areas with spotty power service at best, and certainly not up to our electrical code standards. Would I use an SGPV in such a place. Certainly.

[ggunn]

Funny you should pick that analogy because that's exactly what Chuck Yeager did for a living. Oh wait. Actually, the planes he flew in did explode most of the time...

As I stated before, science can give us the facts, but it can't tell us what an acceptable risk is.

There are areas on the planet that don't have clean running water and flush toilets, areas with spotty power service at best, and certainly not up to our electrical code standards. Would I use an SGPV in such a place. Certainly.

Of course; everything is relative. If everything you have is crap, then yet another piece of crap may be acceptable. If you risk being shot every time you leave the house, risking burning down the house isn't that big a deal.

BTW, do those things shut off when the grid goes down? If so, then it won't help with the spotty power. If not, well, then there are other problems. The most commonly cited one is that you can potentially electrocute line workers trying to restore power, but one which is seldom mentioned though which seems to me a lot more likely is that if everyone around you still has their disconnects closed, then your system would be pretty much connected to a dead short.

Also BTW, the test flights that ended in disaster attracted a lot of attention, but most were successful. I still wouldn't do it, though.

[Sparkletron]

Some of them do; that's one of the safety features. It would help in a brownout.

[ggunn]

Some of them do; that's one of the safety features. It would help in a brownout.How so? Either it will just match the voltage it sees or it will try to raise the voltage of the grid. Either way, no help; you cannot boost the voltage in your house over the line voltage while you are connected, you cannot run a PV inverter offgrid without batteries, and 250 Watts isn't going to help the grid. Help me out here; I cannot envision a scenario whereby one of these things helps spotty power service.

[Sparkletron]

Depends how big your "grid" is. For a village generator in the middle of Africa, 250W may be just the ticket.

[BB.]

And if enough people on a village generator install GT inverters--They may damage the genset as it back feeds it (or they may take the voltage too high and/or take the frequency out of range fault the GT inverters (no damage, just 5 minute timeout)....

However, most "simple" gensets do not have stable enough frequency to support a GT inverter set to specifications (+/- about 1% frequency). Inverter-generators have very accurate frequency--Don't know how they would respond to being back-fed.

-Bill

[ggunn]

Depends how big your "grid" is. For a village generator in the middle of Africa, 250W may be just the ticket.Or maybe not. I remain skeptical. A power grid, large or small, is maintained through a balancing act between supply and demand. One thing that enables residential PV to work here in the US is that the grid is comparatively huge and a residential system going up or down doesn't measurably affect it. In a situation you describe where (if) 250W is a significant portion of the grid, that 250W turning off and on may be more a destabilizing factor than a help. Also, in a situation like that I would expect that most of the loading on the grid would be at night for lighting (I don't expect that there will be much air conditioning in that African village) when your system is off line.

[erikkiehle]

Would you fly on a plane that doesn't crash "most of the time"? :D

Sorry guys, have a compulsion to point out that as far as I know EVERY commercial aircraft model has crashed at some point. So if you fly at all, you're guaranteed to be flying in a plane that doesn't crash "most of the time". Acceptable risk and all that. You could say the same. Your favorite car doesn't crash "most of the time" but there's still that risk .

The Boeing 737 is the most successful commercial aircraft in the history of aviation. Something like 4000 have been built and flown extensively. If you want to get scared, just look at this list of fatal 737 crashes. Sure, it doesn't crash "most of the time", but.... http://airsafe.com/events/models/b737.htm

Ugh, sorry for the "Sheldon Cooper" moment!!!

[ggunn]

Sorry guys, have a compulsion to point out that as far as I know EVERY commercial aircraft model has crashed at some point. So if you fly at all, you're guaranteed to be flying in a plane that doesn't crash "most of the time". Acceptable risk and all that. You could say the same. Your favorite car doesn't crash "most of the time" but there's still that risk .

The Boeing 737 is the most successful commercial aircraft in the history of aviation. Something like 4000 have been built and flown extensively. If you want to get scared, just look at this list of fatal 737 crashes. Sure, it doesn't crash "most of the time", but.... http://airsafe.com/events/models/b737.htm

Ugh, sorry for the "Sheldon Cooper" moment!!!Allow me to rephrase my statement. Would you fly in a plane that doesn't crash on 95% of its flights? Better? :D

[Mike at Energy Commission]

Looks like "plug in to the wall socket" technology like the Chinese versions are now legal in Germany. http://cleantechnica.com/2012/12/20/plug-save-new-diy-solar-systems-from-germany/ I have heard they are legal in Australia as well, I haven't been able to verify that yet. Sure would be nice of they made these legal in the U.S. then apartment dwellers and low income folks could get in to the solar fun.

[BB.]

Plug in Solar will never be safe in the US/North America with our current electrical code.

Basically, you have 15 amp breaker from the utility, and up to 15 amps of power supplied by the "plug in" GT Solar system.... That is 30 amps continuous power available on a a 14 AWG wire. Enough to overheat and cause a fire.

if somebody put a 1,500 watt heater on the same circuit, one could pump >40 amps into that branch circuit and not pop a breaker or fuse.

That is why a building permit and inspection (along with its own NEC code section) is required.

And I could not see where these issues have been addressed in Germany either. Eventually, some bad stuff will happen.

Add mounting requirements (winds/hurricane/roof loading), lightning protection (don't want to bring strike energy into the apartment), etc... I could understand making the paperwork cheaper/easier, but it will never be plug and play unless new home are pre-wired with roof outlets and roof hard points. Certainly doable--But not likely to happen without more laws.

And given that the utility wants/needs to know who has solar (billing, meter, fraud prevention, insurance, code checks, infrastructure design, etc.), there still will be paper work requirements on the utility side too.

-Bill

[icarus]

You could "solve" it by plugging in to a dedicated circuit that has only one, dedicated receptical. For that trouble, use an conventional inverter.

Tony

[Mike at Energy Commission]

I haven't seen the schematics for he German plug and play, I assume the overload danger that is inherent in the current Chinese versions has been mitigated in the German version. If so it would be nice to see how they did, it circuit monitor of some type, maybe? I think plug and play would be boom to solar adoption if the risks could be worked out, the guy that patents the solution will do well. The beauty of plug and play is feeding into the grid without the soft costs and brings it all into a smaller scale, providing access to PV solar generation to a very large market. Possibly the grid operator could come up with an affordable documentation and commissioning program.

[Cariboocoot]

It is not possible to mitigate the overload danger because the danger is in the wiring, not the unit. As Tony said, the only way to alleviate it is with a single, dedicated circuit for the inverter - the same as any GT inverter requires. So where is the plug-n-play advantage then? There is none.

If a company wanted to develop a modular system that connected via a dedicated line and allowed inverters to be added as funds were available ... oh wait; they've already done that with microinverters.

If you want to get into it one small step at a time, go with the legit wired-in system.

[gww1]

I have had two of the gti's pluged in for over a year. (living dangerously "stupidly") I have never had a real system yet due to being in a differrent state due to work.

I must say I think they are the neatest thing if they could be made to work. I am probly paying to use it cause I don't know what my meter does. I will say the power through a kill-o-watt meter has been dismal for what the imput to the device says it should be. The fan runs alot but the air doesn't feel hot. It seems to be about a 30 % convertion rate, instead of the 95% percent they advertize.

I can't wait to install my signature system and hope it works better then the junk I have been playing with. If I don't go to jail, I have had some fun with my expensive toy.

I do wish more could be done to make solar and wind easier to play with and simpler to use in smaller incriments with out having to plan your all time system based on loads.

No batteries, If they converted at 95%, few fantom or inverter idle loads till needed.

Also, even though enphase has many atributes you still have to keep the system together in one spot rather then finding a hole here and a hole there to place panels.

I am not advocating the use of these devices even though I did do it. If I could and if they seemed to work better I would like to be able to.
Cheers
gww

PS I will say that even if you used ul approved equipment and installed it to code, you may still have the same problim with your electric company and insurance if you don't get the proper permission and jump through the proper hoops. The people with the money have the power in this free country. I like it here better then other countries I have been so don't take my statement out of context. Always room for improvement though.

[gww1]

Off subject but one thing I wish someone would invent is a grid tie system that would let you feed your house up to the loads you were using without sending extra back to the power company and without having to move your loads to sub-panels.
gww

[ggunn]

Off subject but one thing I wish someone would invent is a grid tie system that would let you feed your house up to the loads you were using without sending extra back to the power company and without having to move your loads to sub-panels.
gww
Xantrex has that but it's a battery system and it's not cheap. The problem is that without batteries a PV inverter is a current source device and must deliver the total output of the PV somewhere. If your loads are less than the inverter output, the excess goes to the grid. The other thing is that without using subpanels, the inverter has no way of knowing how much of the load it sees is local and how much is the grid.

[gww1]

ggunn
What does the Xantrex system do that is differrent then the outback that I have?

You mention also;

If your loads are less than the inverter output, the excess goes to the grid. The other thing is that without using subpanels, the inverter has no way of knowing how much of the load it sees is local and how much is the grid.

Does the Xantrax have this problim? How does it work?
Thanks
gww

[ggunn]

ggunn
What does the Xantrex system do that is differrent then the outback that I have?

You mention also;


Does the Xantrax have this problim? How does it work?
Thanks
gwwI am no Xantrex expert, but my understanding is that if you don't turn on the "sell" mode it will not export power from its AC1 port.

[inetdog]

The other thing is that without using subpanels, the inverter has no way of knowing how much of the load it sees is local and how much is the grid.
Does the Xantrex have this problem? How does it work?
Thanks
gww
If the inverter is connected to both the grid and local load at a single connection point (like a backfed breaker) it has no way of knowing where its output is going. The Xantrex forces you to wire the incoming grid connection onto one set of terminals (AC1 or AC2) and to connect the load to a different set of terminals (AC Out). That way it can use internal circuitry similar to that in a regular power meter to determine which direction (overall) the AC power is flowing.
One of the things that ggunn is referring to is that to do this either the Xantrex must be capable of handling the entire supply current to your home through its internal transfer switch and wiring (meaning a relatively small set of house loads and a small service panel) or you must split up your loads so that only a subset which is within the Xantrex transfer switch's rating is being powered from the AC inputs.
The former is usually not a problem for an off-grid home that has a generator, but is rarely if ever met with an on-grid home with conventional wiring.

[gww1]

ggunn
I am even less of a Xantrax expert as I did not understand the meaning of your answer. I guess I need to look up a Xantrax manual and read it. It sort of sounds like turning the sell off the outback system. It would be neat if you could set the outback to sell but put some kind of control at the meter that let none of the power go back but only forward. Then the grid could help support the load shortfalls but you would get full use of the pv power. I saw a disscussion on the outback technoligy forum where there was software getting close to doing this but not close enough that some power didn't slip through to the grid, there for, making a grid tie agreement with the power company still needed.
Thank you for your responce
gww

[gww1]

Inetdog
Basically it works just like the outback.
Thanks
gww

[DaveB]

ggunn
I am even less of a Xantrax expert as I did not understand the meaning of your answer. I guess I need to look up a Xantrax manual and read it. It sort of sounds like turning the sell off the outback system. It would be neat if you could set the outback to sell but put some kind of control at the meter that let none of the power go back but only forward.

This was originally considered years ago by Outback but they determined there was not enough interest in it by installers to add this feature. I sure would have liked this feature.

[tallgirl]

This was originally considered years ago by Outback but they determined there was not enough interest in it by installers to add this feature. I sure would have liked this feature.

I messed with adding a feature to do that a few years back. The greenMonitor software would calculate the 6 hour projected production and consumption and make DROP / USE decisions based on that. It even worked fairly well -- I greatly reduced the amount of energy I was selling to the PoCo. Then I got a Mate 3 and it didn't take commands at the time, so I stopped bothering.

I'm not sure it's worth it. It cycles the batteries almost as much as an off-grid home and that's not the easiest thing in the world on batteries. Since the spread between BUY and SELL is $0.033 / kWh for me, it's REALLY not worth it. It was especially hard in the Spring and Fall when consumption was closest to production. I was cycling to 80% SOC every day just so I'd have spare capacity in the batteries for what would get produced the next day.

[inetdog]

I'm not sure it's worth it. It cycles the batteries almost as much as an off-grid home and that's not the easiest thing in the world on batteries. Since the spread between BUY and SELL is $0.033 / kWh for me, it's REALLY not worth it. It was especially hard in the Spring and Fall when consumption was closest to production. I was cycling to 80% SOC every day just so I'd have spare capacity in the batteries for what would get produced the next day.
With some credible estimates of the combined cost of PV and battery cycling ranging from an absolute low of $.50/kWh up as high as $2.00/kWh, you really should believe that it is not worth it.

It seems best suited to people who not only cannot get Net Metering but are not allowed to push back power at all. Sort of a capped grid tie situation, with the idea of never actually cycling batteries if possible.

[gww1]

Tallgirl and inetdog
I still think it would be neat for someone who isn't going to be grid tied due to poco having rules against things like homemade wind turbins and such. Or for those who just don't want the hassel of jumping through all the hoops that poco puts out there. If I remember correctly tallgirl you did a little aurguing with the powers that be which is why you were inventing the software. If you are going to run as off grid but want to keep your grid backup I think it would still be neat. I don't know if the demand would justify it though.
gww

[tallgirl]

With some credible estimates of the combined cost of PV and battery cycling ranging from an absolute low of $.50/kWh up as high as $2.00/kWh, you really should believe that it is not worth it.

It seems best suited to people who not only cannot get Net Metering but are not allowed to push back power at all. Sort of a capped grid tie situation, with the idea of never actually cycling batteries if possible.

That absolute low value is entirely too high. I'd believe that for a pure off-grid environment where there's no choice but to cycle to a lower SOC or turn on a generator, but not for what I was doing.

The key cost drivers I see for this sort of application is buying "Cadillac" batteries (top of the line "solar" batteries) when "Chevy" batteries (the much maligned Sam's Club golf cart batteries, as an example) are more than sufficient.

For that matter, the key cost driver for solar power installs in a grid-tied environment is buying "solar" batteries and following the conventional wisdom about replacing batteries. Everyone that I know, without exception, who bought a bank of "cheap", "non-solar" batteries for whatever reason has found that they lasted far longer than expected and had a lower annualized cost than major brand "solar" batteries.

For off-grid installations I'd still recommend major brand batteries, but for grid-interactive, battery-backed systems I'd recommend something in a golf cart battery from Sam's Club or other golf cart supplier.

[BB.]

When I do the cost calculations, I also add the cost of the entire installation (including charge controllers, AC inverters, etc...) and assume that batteries have an X year (or YY year for "better batteries") replacement and "budget" a 10 year life for the charge controllers/inverters (may last longer, but not always).

Add that is is (for most people) to actually use 100% of an off grid system's available power (batteries are full, where does the "excess" charging power go) throughout the year (i.e., 66-75% of available power is used on average for a full time occupied off grid home0:confused:) also increases the $$$/kWH power costs.

Anyway--I just use those numbers as a starting point to see if an off grid system is practical for the application (and to suggest that conservation is also a very good investment for time and money too). As always, do the detailed design/calculations and figure out "your" $$$/kWH costs (or whatever number(s) make sense to you).

-Bill

[NorthGuy]

Cost per kWh only make sense when there's a linear depency of cost on number of kWh used. In off-grid system, you generally pay nearly the same regardless of what you use. If you conserve energy, you use less kWh and your price per kWh go up. Only if your system is undersized and every new kWh of usage comes from running a generator, then cost per kWh may make some sense.

If you want to compare to the grid, off-grid system has high "connection fee", small "monthly" fee and very little (or none) cost per kWh.

If electric company says you need to pay $100K upfrunt, then monthly connection fee, and, on top of this, $0.10 per kWh, then off grid would have much smaller upfront fees, much smaller connection fee, and almost no cost per kWh.

That said, my off-grid "price per kWh" is around $0.30. If I lump up the electric company monthly charges with energy charges and divide by the number of kWh used, it's more than $0.30 (and that doesn't include upfront fees!).

[BB.]

True, $$$/kWH is a bit artificial... And "all chargers" (i.e., distribution charges, taxes, billing charges, minimum billing, etc.) all need to wrapped together to give a "more real" number for utility charges (depends on your utility).

However, $$$/kWH still gives a good way to compare choices. For example, a desktop computer running 200 watts * 10 hours per day vs a laptop that uses 20 watts:

0.200 kW * 10 hours * 365 days a year * $1.00 per kWH = $730 per year power costs (desktop)
0.020 kW * 10 hours * 365 days a year * $1.00 per kWH = $73 per year power costs (laptop)

So--The extra $400 for a laptop computer to do the same work makes a lot of sense (off grid).

If you run the same numbers for on-grid usage at $0.20 per kWH:

0.200 kW * 10 hours * 365 days a year * $1.00 per kWH = $146 per year power costs (desktop)
0.020 kW * 10 hours * 365 days a year * $1.00 per kWH = $14.6 per year power costs (laptop)

That extra $400 laptop premium is going to take a lot longer to recover.

Again--just an example of how to do quick back of the envelope calculations and I why like to give a, very rough, estimate of off grid power costs (including battery/charge controller/inverter replacement costs every ~10 years or so--Batteries may last ~3 to 20+ years, depending on what you purchase).

And, there are those "murdered" battery banks when somebody or some hardware "goofs up"--A small battery bank costs less to replace after those events (not uncommon for the first time off-grid person--although it has been known to happen to experienced folks too:cry:).

-Bill

[NorthGuy]

However, $$$/kWH still gives a good way to compare choices. For example, a desktop computer running 200 watts * 10 hours per day vs a laptop that uses 20 watts

Only on grid, where you literally pay for the kWh used.

Off-grid is different. kWh usage by itself is not a dominant factor anymore.

If you already have a system big enough to run a desktop computer, replacing it with laptop will not bring you any savings.

Moreover, such a huge load as 2kW Air conditioner, if set up to run as a diversion load during summer excess, may cost you less than 2W night light which is on during long winter nights.

[BB.]

True---But a desktop computer (in this example) is no small load (can be more than 2 refrigerator loads).

Again--I was just showing how somebody can make "monetized" decisions. If the system can support a new desktop computer--then is possibly started out over sized.

I suggest 3.3 kWH per day (100 kWH per month) is a fair sized off grid system for a small energy efficient home... Throwing a desktop computer used 10+ hours per day can almost double the power usage.

In the end, power usage is a highly personal choice... I am not trying to suggest a "moral" or "green" way of living one's life--Just some different tools to help make those decisions.

-Bill

[NorthGuy]

I suggest 3.3 kWH per day (100 kWH per month) is a fair sized off grid system for a small energy efficient home... Throwing a desktop computer used 10+ hours per day can almost double the power usage.

There's another aspect to it. The smaller the system, the higher the cost of kWh it is capable of producing. Therefore, people who have larger system will have lower "per Kwh" cost and it is easier for them to beat the grid pricing.

[ggunn]

There's another aspect to it. The smaller the system, the higher the cost of kWh it is capable of producing. Therefore, people who have larger system will have lower "per Kwh" cost and it is easier for them to beat the grid pricing.By the same token, someone who buys too large a system for their needs will likewise be paying more per kWh than someone whose system size is well matched to their usage.

[NorthGuy]

By the same token, someone who buys too large a system for their needs will likewise be paying more per kWh than someone whose system size is well matched to their usage.

Sizing is everything. Whether you build it too small or too big, you will end up paying more. Easier said than done :D

The huge advantage of the grid is that you need to size anything except main breaker, which is easy to re-size.

[tallgirl]

That's why I replaced my old non Energy Star rated fridge with one that was and sold the old one. My current fridge draws about 130 watts on a 45 to 50% duty cycle. The old one was MUCH higher. The Energy Star "rating" was around 475kWh per year, but I set it colder than "economy" because I used to have two teenagers living here. The old one was something like 1,200kWh per year.

[NorthGuy]

That's why I replaced my old non Energy Star rated fridge with one that was and sold the old one. My current fridge draws about 130 watts on a 45 to 50% duty cycle. The old one was MUCH higher. The Energy Star "rating" was around 475kWh per year, but I set it colder than "economy" because I used to have two teenagers living here. The old one was something like 1,200kWh per year.

Yep. I bought a new efficient fridge. It is twice as big as the old one (30 years old), but consumes only about 1/2 of what the old did.

[tallgirl]

Yep. I bought a new efficient fridge. It is twice as big as the old one (30 years old), but consumes only about 1/2 of what the old did.

I wanted the one I bought because it has "French Doors" and will hold just about anything. My old fridge was a side-by-side and it was a tight squeeze for many larger items. That it sips electricity is an added bonus.