Intermittent Voltage Dropout Xantrex 4048 plus

[muirhouse]

I am having a voltage dropout problem. Two Xantrex inverters, SW4048,4048plus stacked mode, Genset is Hardy Diesel 15kw, 60A. 16 Surrette batteries, 48V setup, series, parallel.

I have called Xantrex, they say they have never seen this problem. We are going to check to see if perhaps we have two neutral-to-ground bonds that could be causing this, it is the only thing we can think of, but nothing else is acting up. We first noticed this on an outlet one away from a GFI. The radio there kept turning on and off. During DX of this, if I plugged a light into the same outlet, the problem routinely disappeared. So, a resistive charge stabilizes it. Does that tell us anything?

On the Inverter side: The Invert Light on the 4048 plus pulses and buzzes every few seconds, while the voltage readout goes from 119 to 0 and back. HZ levels stay constant. The problem corrects itself, but is chronic, keeps happening. Does not seem to be related to where we are in the cycle of charge, recharge.

Anyone had a problem like this? Not sure what to do!

[BB.]

It sounds like Search Mode is turned on (inverter off, turn on and see if >6watt load, turn off for a bit if less than 6watts and wait, turn back on look for >6watt load, etc).

How is the Search Mode programmed...

What are the other loads at the time (radio only, or other loads running too). Is it the branch circuit behind the GFI outlet that "fails" or is it everything on that inverter?

Has it worked before (months/years) or is this a new/upgraded/modified install?

Is this a grid tied system, or completely off-grid?

-Bill "lots of questions, few answers" B.

PS: Are you having any problems with the GFI outlets that you can see? I am not a big fan of placing GFI receptacles everywhere--just where needed (near water).

[muirhouse]

BB-

Inverters are in SRCH mode, instead of ON, as this uses less power. I can see if this goes away if I set inverters to ON. The 4048 itself, that controls generator is not doing this.

This is a new-ish problem. I think SRCH watts set to 48, the default. Can I set one inverter to SRCH, one to on?

GFIs are only at water points. It is sensitive electronics on that 4048 Plus inverter (radio, fluorescent light, Rinnai propane heater, fire alarm monitors.) Non grid tie.

[BB.]

I know next to nothing about the details of these inverters... So, somebody else will have to help you there.

I agree that search mode saves lots of power... If set to 48 watts--Do you need it that high? It sounds like you have lots of "small loads" (water heater, fire alarm, etc.)...

Perhaps, moving these small loads to a small inverter that you can leave on 100% of the time--if needed (hopefully with less losses at low power levels)--would be a help?

Have you changed/added any loads recently? Any of them behaving "strangely"?

Any recent nearby lightning strikes/power surges (genset going crazy, etc.) that may have damaged some electronics?

-Bill

[muirhouse]

OK, good idea, lower search watts. And try with SRCH off. That will give more informaton. But any idea why the resistive load makes the dropout stabilize? The only new load is a ceramic kiln, but we never run this without the generator on.

[BB.]

A lot of your loads are "electronic" and may have poor power factor ("current spikes" only at the crest of the sine wave).

If you have a well pump (240 VAC stacked operation?)--The stray inductance plus the poor power factor of some of your loads can actually set your system up to "ring" (oscillate) from all of these non-linear loads. Adding a resistive load adds "damping" (like shock absorbers on a car) to your system and, may, be helping reduce the oscillating effects.

If you have 240 VAC inductive loads--try switching them off (even is one of the inverters is in standby/search mode) and see if current down long wire runs/inductive loads help resolve the issue.

Just guessing here.

-Bill

[muirhouse]

Yes, 240 is for well pump, and now for kiln also.

Let's see if my lowering the search to 16 from 48 does the trick. It may be that I set the mode to SRCH from ON around the time I began noticing this problem. For the longest time I just thought it was that one outlet and it was the radio that was defective and didn't go looking for anything else.

If that doesn't do it, I will look further at your last suggestion. I will let you know tomorrow! Thank for the input, didn't even think of SRCH setting.

[RCinFLA]

Couple of details not included in your post.

Are you on generator or grid when problem occurs?

Approximately how often does it occur? Any alarms show up?

Have you noticed which 120v side dropout occurs, or both. Is the buzzing dominated by one of the units?

The two inverters operate pretty much independently. There is a control to enable/disable both when turning off and on units and when without grid or generator there is a sync line that keeps the two 180 degrees out of phase to produce net 240 vac across the two ACout terminals. ( still 120v to neutral).

Do you have both temp sensors attached? Might remove them for a while to see if issue goes away. If one sensor goes bad it can cause heavy charge or discharge (within setting of max AC input and max AC charging settings). This only applied to when gen or grid active.

Lastly, and most gloom, it may be a MOSFET going bad causing excessive current draw. There are three sets of MOSFET H-bridges, one for each power transformer. (Pappa bear, Moma bear, and baby bear). Total of 42 power MOSFET's A bad wiring connection to these MOSFET's or transformer has the same effect.

I had a SW5548 plus do a similar thing. (two units series stacked) After about a week of intermittant buzzes it finally blew. See attached picture of MOSFET board.

[solar_dave]

I sense the release of the magic blue smoke in that picture!

[muirhouse]

Dear RCinFLA,

Checking in to check old posts and beg for help on the new one I find (of course!) everything is connected to everything else. The 'excessive current draw' of your October4 MOSFET blowups leapt of the page! But first things first.

To answer your questions: I am not on the grid at all. The voltage dropouts happened when the generator was NOT charging, and so my conclusion to the problem has for the last two weeks been, the SEARCH mode was set too high. This really does not make sense actually, but lowering it to 16 does keep it from happening. I tried upping it to 32, but it happened at 32 also. 16 is what it is happy with.

It was happening several times a day, no rhyme or reason, and no alarms, just appliances going off, and YES, all of this was on one inverter, the SW plus, the non gen controlling one, and yes, it was buzzing with each flash of the invert light.

I love the "most gloom". What the heck is a MOSFET, do I have one somewhere in there?

Here's the reason the 'excessive draw' jumped out at me: I am here in the 11th hour, with my $6K new hampshire state rebate having been approved, trying to decide if I should plunk down money to add the approved 2.7KW 12 Schott panel PV system with charge controller. At a cost of $14,500. And then turn around and have the mosfet blow, or the generator finally give up the ghost (is is a HARDY SOLAR shanghai diesel and I have spend bucket on repairs. It has been a good girl for months now, but that has been unusual).

What really threw me today was my installer telling me that I would save $100 a month on my diesel bill. I realized that I was really expecting the solar to cut my bill by way more than only $3 a day! When I sat down and worked it backwards (the gen is coming on every 12 hours, runs for 3 hours or so to get up to 58 before going to float). Diesel is $3.20 delivered here in NH, so at 3 gallons per run and two runs that is almost $19 a day, $570 a month, very steep, but getting the grid up here is impossible. I am just stuck. But now I am just sure that this generator shouldn't be running this much, and and the possibility of some phantom energy suck becomes reality with your MOSFET debacle. There is a twisted story behind this system, and chasing all this stuff down is about to be the end of my psychic endurance!

Help.