100 amp service panel upgrade for PV install

browayjr

So getting ready to purchase 13kw solar w/ 2 x 7.6 sokaredge.
We need 2 x 40 amp breakers = 80 amps.
Here's my issue. The property has 100 amp service. With 100 amp panel. We want to replace the old zinco 100 amp panel anyways.
My thought was to purchase a 200 amp panel and downgrade the main to 100 amps. With this setup my solar will not exceed the 120 rule for the bus bar rating.
So I just wanted to open up a discussion and see if anyone with experience has any reason this shouldn't pass inspection!
Is that anything in nec guidelines that won't allow this?

Ethan Brush

That is a common solution and likely what i would do. Note that a 100 amp breaker is a different frame size than a 200 so most likely you will buy a main lug panel and buy a 100 amp 2 pole and backfeed it as your main. Dont forget the hold down screw for the backfed main.

BB.

Make sure your building department/permit folks will sign off on this... And your utility may have some issues too (make take them some time to "approve" your planed changes).

And you may think about a 150 Amp main breaker... That would should allow you an 80 amp GT array branch circuit and still be under the 120% rating of a 200 amp box--Plus give you some additional main service capacity over your existing box.

-Bill

Ethan Brush

BB. said:

Make sure your building department/permit folks will sign off on this... And your utility may have some issues too (make take them some time to "approve" your planed changes).

And you may think about a 150 Amp main breaker... That would should allow you an 80 amp GT array branch circuit and still be under the 120% rating of a 200 amp box--Plus give you some additional main service capacity over your existing box.

-Bill

I was originally going to suggest using a 125 breaker for the main.  125 is the max 2 space breaker you can get, above that they take up 4 spaces and there is a HUGE price jump.  The best way to go with a 150 if deemed necessary would be to buy a 200 amp main breaker panel and a 150 main breaker (same frame), swap the breakers and throw out the guts of the 150.  Or just use the 150 and say you swapped the breaker if asked since its the same bus on both panels anyway.  But note that he would have to then upgrade the service entrance and probably the meter socket and I wasnt sure if that was part of the plan.

Note: response is considering square D equipment.  I am not as familiar with other brands.

ARTsolar

You have a lot of inverter for your 13 kw of solar. What I might do is knock your 7.6 inverters to a couple of 6's. Then if you look at your max current connected to your AC panel we would be talking about 62.5A (25+25)*1.25. With your service upgrade go with a panel that has a 200A main breaker and a bus rating of 225A, install your PV breakers at the opposite end of the bus and you are good up to 70A of PV inverter output.

solar_dave

ARTsolar said:

You have a lot of inverter for your 13 kw of solar. What I might do is knock your 7.6 inverters to a couple of 6's. Then if you look at your max current connected to your AC panel we would be talking about 62.5A (25+25)*1.25. With your service upgrade go with a panel that has a 200A main breaker and a bus rating of 225A, install your PV breakers at the opposite end of the bus and you are good up to 70A of PV inverter output.

Yep ART is right.  Your panels will only put out about 80% of the face value or 10400 watts.  I have my 12.5 Kw system on a pair of 5200 inverters and have only seen it clip the output for about 30 minutes once on a cool clear day in the spring when the panels were pretty lined up with the sun.

sub3marathonman

solar_dave said:

ARTsolar said:

You have a lot of inverter for your 13 kw of solar. What I might do is knock your 7.6 inverters to a couple of 6's. Then if you look at your max current connected to your AC panel we would be talking about 62.5A (25+25)*1.25. With your service upgrade go with a panel that has a 200A main breaker and a bus rating of 225A, install your PV breakers at the opposite end of the bus and you are good up to 70A of PV inverter output.

Yep ART is right.  Your panels will only put out about 80% of the face value or 10400 watts.  I have my 12.5 Kw system on a pair of 5200 inverters and have only seen it clip the output for about 30 minutes once on a cool clear day in the spring when the panels were pretty lined up with the sun.

I'm not sure that 80% is right.  I've seen many, many times where mine, here in Florida, are doing 100%, and on a few rare occasions even about 105% to 107%.  Yes, it has to be a cool/cold day here in Florida, but they do happen.  By chance, there was another topic recently about PV panel output, so I decided to check and that was one of the times it was over 5kw for a 4.7kw system.  Now yes, during the hot summer, spring, fall, and part of the winter  the panels are putting out around 80% instantaneous maximum for the day.