How to add more PV? 200 Amp Mains panel with 4.6KW PV on circuit breaker

[Bill SEPA]

I want to add 6.6KW of additional panels to a grid tie set up that already has 4.6KW connected through the Main panel (200amp) via a 40amp circuit breaker. One installer proposed connecting on the Load side or line side, which he explained would not be in the panel box or have a circuit breaker? Is this safe? What are the down sides? how do I learn more about this type of set up.

[solar pete]

I want to add 6.6KW of additional panels to a grid tie set up that already has 4.6KW connected through the Main panel (200amp) via a 40amp circuit breaker. One installer proposed connecting on the Load side or line side, which he explained would not be in the panel box or have a circuit breaker? Is this safe? What are the down sides? how do I learn more about this type of set up.

Hello Bill and welcome to Solar Panel Talk.

What you are saying doesnt sound right, (but I am in Australia and rules and regs are different) at the very least I would ask your local POCO, as I think unless you got approval for the larger system at the start, I think there will be additional paperwork and processes to go through. Someone should pop in that knows a bit more at some stage. I think we will need more info from you like where are you and maybe more specs of the system. We have had some technical issues so it may be a bit longer than usual, cheers

[bcroe]

I want to add 6.6KW of additional panels to a grid tie set up that already has 4.6KW connected through the Main panel (200amp) via a 40amp circuit breaker. One installer proposed connecting on the Load side or line side, which he explained would not be in the panel box or have a circuit breaker? Is this safe? What are the down sides? how do I learn more about this type of set up.

What inverters might you use for 6.6 + 4.6KW? String or micros? Does your PoCo contract
cover the situation?

There is a belt & suspenders rule that the inverter feed in breaker can't be more than 20%
of the main breaker, so the total current can't overheat a section of busbars by ADDING
TOGETHER with a heavy load applied. AND that the inverter feed in breaker must be at the
opposite end of the bus bars from the main breaker, so that the 2 sources CAN'T ADD
TOGETHER feeding heavy loads. Bruce Roe

[solarix]

To do a standard load-side tap, the backfeed rule in the NEC says your solar backfeed cannot be more than 20% of the busbar size plus whatever difference there may be between the busbar size and the main breaker. For a 200A service (usually the size of the main breaker and the busbar), this means your backfeed breaker is a maximum of 40A and the inverter max output current is 40 x 80% = 32A (or 7.7kW). To go more than this you have four options:
1) Upgrade the panel to 400A (which is really two 200A busbars - one of which you would dedicate to solar).
2) Do a line-side tap before the main breaker. (which very few service panels are listed for and requires a separate permit to get the utility out to interrupt the service)
3) Install a new meter socket product that backfeeds the solar power through it. (very new, and I'm not sure its available yet)
4) Derate the panel by putting in a smaller main breaker. (many panels don't have main breakers in say a 175A size, you need to prove to your AHJ that it can handle your loads by doing a code approved load analysis and it requires a separate permit to shut your power down while it is installed). A 175A main gives you 25A more backfeed. 25A + 40A = 65A x 80% = 52A x 240Vac = 12.5kW of inverters.

You need a competent installer to not muck this up.

[peakbagger]

The local utility in my area got burned by solar installers making line sized taps inside the meter enclosure. They insist that the line size tap be installed in a completely separate enclosure downstream of the meter.

A competent electrician apparently should know better but shortcuts get taken.

[Naptown]

A line side tsp is very common.
Also as others have said defeating the main breaker also works.

[skipro3]

Just derate the panel from 200 watt to 150 watt by replacing the main breaker with a 150 amp breaker. It will pass code inspection and most important, it is safe.

[foo1bar]

Also as others have said defeating the main breaker also works.

derating the main breaker is what Naptown meant.
I'm sure it was a typo/autocorrect.

(Hopefully no one read that and thought it really should be "defeating" - because defeating a main breaker is obviously just a bad idea.)

[bcroe]

derating the main breaker is what Naptown meant.
I'm sure it was a typo/autocorrect.

(Hopefully no one read that and thought it really should be "defeating" - because defeating a main breaker is obviously just a bad idea.)

I would certainly like to know how to DEFEAT this thing that keeps changing what I type
without my permission. Bruce Roe

[Bill SEPA]

WOW. Thanks for the information everybody.

To answer the question about the inverters. The 4.6KW system uses an SMA Sunny Boy 5000 and has been working great for 5 years so far. The proposed 6.6 system will use an SMA Sunny Boy 7000.

The more I read here the more I learn. I just don't want to burn down the house by overloading what I already have. I will talk to the installer again to be sure there is an understanding about that.

SO, the question becomes......Would you upgrade to a 400 amp panel or do a line side connection? I will start a new thread with that question to comply with standard forum protocal.

Thanks again everybody.

[Naptown]

A line side tsp is very common.
Also as others have said defeating the main breaker also works.

Yes I meant de rate
Dam autocorrect