Upsizing my main breaker to 200A -- solar says do not upsize

125mph

I got my panels installed in 2014... right now I'm in the middle of constructing an addition.. My contractor looked at my electrical panel and it there's text that says "Main breaker has been downsized to 150A. No up-sizing permitted".

I think the solar installers downsized my 200A to 150A due to inverter overcurrent... how do I get 200A? My new addition is planned to bring in 100A from the current house to the new addition, but that leaves only 50A in the old house. My contractor says he needs to upsize the main breaker to 200A to satisify the inspector but he isnt familar with what that will do to the solar. I just contacted my solar installers but wana see what you all knew!

THanks,

solar_dave

How much solar do you have?  A 200 amp panel should be able to take up to a 40amp back feed without downsizing.

I just had to roll with a device entrance upgrade to 400 amps (dual 200 amp on a 400 amp metering bus bar) because to the loads on my 200 amp load center would not allow the needed downsizing to 175 amps per the code dude.  I took a $4000 hit on that one but because it was determined to be part of the solar install I got the 30% tax credit. They retrofitted the wiring all the way back to the transformer.

I didn't holler too loud cause I knew in a year of so I would add a 60 amp sub in the garage for the electric cars and a 125 amp sub in my new workshop/man cave!

125mph

Its just a 6.3kW system.... 30 kyocera panels with two inverters.

So basically, what will happen if my contractor upsizes the main breakers back to 200? I'm not sure why the text by the panel says "Main breaker has been downsized to 150A. No up-sizing permitted".

solar_dave

SO that would be about 27 amps, the code has been that the solar connected to the opposite end of the buss bar can be up to 20% of the buss bar rating while not having to down size the main breaker.  So a 200 amp buss bar should be able have a 200 amp main and a 40 amp back feed simultaneously. You will have to go to the local agency having authority over the code and get them to agree however. 

BTW what is the breaker size on your back feed, if your inverter is rated for more than 40 amps then "boom" a down size for sure as they rate the breaker by the device size not the solar output.

You could try and make it part of the permit on the new building.

125mph

I'm not an electrician so I have no idea what you're saying hehe.. But basically, if my contractor can get the inspector to okay upsizing to 200A, will there be any issues with the solar not working? What are the ramifications of this modification other then local agency and permit stuff?

Basically, here's what happen.. The architect wrote on the plan that the new construction will have 100amps taken from the main breaker... But the main breaker is 150amps so they think 50 for the current house isn't enough. So they were planning on upsizing to 200 but they didnt realize the tag saying not to upsize per the solar installer.

BB.

Your solar does not care about the size of the main panel/main panel breakers--The system will work.

What the worry is that with two power sources (your AC mains and your Solar Branch circuits) is that you could get more current "stuffed" into the box than the bus bars can manage.

So, the 150 Main Breaker (per your original installer) is maximum for the 200 Amp main box + solar array branch circuits totaling ~90 amps.

If your Solar Branch Circuits (total of breakers) was only 40 amps, then, it should be "legal" to bump the Main Panel Breaker back up to 200 Amps (you are allowed 120% of main panel rating for AC mains + Solar Branch Circuit Breakers).

In my area, I think that 125 Amp main service is probably the minimum per code.

Ignore the solar breakers for load planning... Is 150 Amps enough for your home?

Is 90 amp total breakers enough for your present and planned GT solar system?

-Bill

125mph

Gotcha! That makes sense.

So the new addition is calling for 100 amps and the older part of the house is probably going to need 100 amps.. My contractor will try to ask inspector to allow 50 amps in the older part of the house for total of 150 amps. But if not, then we need to get 200 amps on the main breaker.. 

I'll check the solar backfeed tonight when I get home... I think they're 20 amps each.

BB.

Remember the "Box" (main panel) is what carries the maximum rating. The breakers installed are no larger than the box rating.

If you need >150 Amps, and have "significant" amount of solar, then you are looking at a larger AC Main Panel and very possibly a new utility drop--And in some cases a new utility transformer (your utility will want their engineers to look at a >200 Amp main breaker most likely).

-Bill

125mph

So I just checked my panel box.. it looks like my solar breakers are 20, 50, 50, 20.. does that mean its using 70 or 140? If its 140, I'm not sure how my main breaker is using 150.

Here's the image:



Also, I got a response from my solar installers.. The guy said one option would be to upgrade the service box to 225 amps, which would allow me to upsize my main breaker to 200. At 225 amps, with 20% over, so that would be 270 maximum?

Ethan Brush

First you would need to know what the total of the solar breakers are.  That is a quad breaker which was likely used because they needed more spaces.  I would guess based on what you said about the system size, that the 50A breaker is for the PV and the 20's are for non solar stuff.  The solar installer was correct in downsizing the pv breaker since, as has been mentioned, with a 200 amp main and 200 amp bus, the max pv breaker is 40.  That said, I am not sure why he installed a 50 and not a 40 - if its a 6.3K system 40 would be fine so you could replace that 50 will a 40 and put the 200 main back in if you want.

That said, Regarding the loads for the addition, I would generally have no problem at all with installing a 100 amp subfeed of a 150 amp panel.  The 100 amp subfeed wont use 100 amps.  The typical home wont ever draw more than 70 amps.  Obviously there are exceptions like lots of air conditioning in a big house, a ton of electric heat, etc.  Perhaps you can turn everything on and meter the mains and that will make the inspector happy (that is not a NEC approved way to determine loading, but it may appease him).  Another way is for the electrician to do a formal article 220 load calculation and see what that comes up with. 

Finally, where is the subfeed breaker going to go, looks like you are pretty full.....