service upgrade required?

[xiphias]

One potential installer has said I need to upgrade my existing electrical service from 100Amp to 200Amp in order to add a ~3kW grid-tie system (Evergreen panels, SunnyBoy inverter).

Another potential installer has not.

Thoughts as to why or why not, and whether/why an upgrade would be needed?

Thanks.

[niel]

i'm not seeing the need for a service upgrade based on just the service ratings as a 3kw solar can work on it. at best if it is a battery backed grid-tie then an added sub panel can be put in. the solar will not add to that which is passing into the house, but would rather subtract from it seeing as how it would cancel out that same amount of power would be needed going inward bound. if the installer is adding the solar current to the overall passing through the main breaker he is wrong and do not go with that installer as he doesn't seem to have enough of a grasp of the basic concepts of what solar is doing imho. 3000w/240v=12.5amps outbound from solar at max output. i think a 100a panel will take it just fine.

[xiphias]

Thanks. No battery backup. Just straight grid tie. This particular installer has done most of the installs in this region, including some pretty complex commercial stuff, wind/solar combos, thermal, PV, etc. He's been around for 20 years. I've seen several of his residential installs and they are quality pieces of work. Never did notice whether they all had 200Amp service, though. Might have to go back to him on this.

[niel]

yes, do ask him why that upgrade is needed as i'd like to know the reasoning he is using.

[crewzer]

Either installer could be correct. The answer lies in two areas:

(1) Is this a commercial or residential installation, and
(2) What size breaker(s) is/are planned between for the inverter feed(s) to the service panel?

Check this Code Corner article by John Wiles for the explanation: http://www.nmsu.edu/~tdi/pdf-resources/CC111.pdf

HTH,
Jim/crewzer

[Solar Guppy]

I would trust installer that has the local experiance, its most likey true due to local inspectors will requiring the upgrade to 200 amp service and what ever they want you have no choice but to comply.

When renovations are done to a structure, its common that services are required to be brought up to the current code standards. I've seen some commerical jobs where the costs to bring a structure to current code was 4X the cost of the actual addition/renovation.

[xiphias]

Thanks for the article. Will give it a read. Both installers are trusted, long-time locals with many installs under their belts. If anything, I think it's likely that the one who did not specify the service upgrade missed noting that we have 100Amp service, not 200Amp, if in fact 200Amp is required.

[niel]

it may be a case that you would need the 200amp service anyway be it from inspectors or that your service was too low in amps for your residence anyway. in actuality, as i had said before, solar does not increase the current flowing through the main breaker so it is not a valid reason for a higher rated service panel imho. however, if inspectors tell you to pick your nose to pass, you pick your nose no matter how unfair or assinine it is to do so. failure to do so may result in not only a failure, but he may require you to pick your seat too!
this is premature imo as this is coming from an installer so please ask him why the need.

[mike95490]

Thoughts as to why or why not, and whether/why an upgrade would be needed?

Profit, or code may require an upgrade when any electrical permit is pulled. Grid-Tie inverter would not matter till you get to about 50A output ( @ 240VAC ) THEN, a 100A panel may need to be upgraded.


Or

Your panel uses old breakers that can't be found anywhere, or has no more empty slots for 2 new breakers.

[crewzer]

solar does not increase the current flowing through the main breaker

niel,

Right. But, adding the output from an inverter can increase the total current flow in the bass bar(s), and that may cause its/their rating to be exceeded. Therein lies the potential problem.

HTH,
Jim / crewzer