QueenBee wrote:So do they also disallow 125 amp panels that a 200 amp main breaker will fit into?! What if someone puts in a 200 amp breaker, think of the children!
They don't, or they don't care. If someone does it and home burns it won't be their problem, the fault will be clearly on the homeowners part. However if someone stays within the panel ampacity but burns underground cables and possibly the transformer, then at the very minimum it becomes their problem for repairs and possibly legal consequences if there is any damage to the property and worst case injuries or deaths as it is no longer all black and white as in the former case.
I disagree that the liability would be different in those scenarios. Just because the panels bus is rated at 200 amps does not mean that the wiring to the meter box, the meter box, the wires to the utility, the GECs, etc, etc. are all rated for that. AFAIC the utility has no more or less liability in those two scenarios. I actually think part of the problem is there doesn't seem to be any good way to know how many amps your service really is, at least around here, and there is nothing in place to protect the service wires. Your utility must be smaller and thus has the time to review panel upgrades and thus enforce this rule? My utility only did three things. Tested the voltage at the meter base and relocked the meter base after we opened it to cut power for the panel upgrade, reviewed the solar generation design, did the same test and installed the new production and net meters. Everything else they just assumed that because the inspector passed it was all fine.
QueenBee wrote:The funny thing is my 1969 house is it came with a split bus panel. The main breaker was 60 amps but the top of the bus allowed for 4 or 8 half breakers. So you could easily add more breakers than the service was rated for. No one cared when I had 30 amp for dryer, 30 amp for old water heater, and new 40 amp for the EVSE and the 60 amp main, all 240 volt.
There is no safety issue with having the sum of all individual breakers exceed the rating of the main breaker. As far as I understand it is fairly typical. The worst that can happen is your main breaker trips if you load several circuits at the same time, no harm is done.
No no, this was called a split bus panel. The main breaker was 60 amps and it only controlled the lower part of the panel. Then the top of the panel had 4 spaces (that could be doubled to control 8 lines, but would be against code as the limit is 5 throws to cut power). If you turned off the main breaker the top 4 circuits remained powered on.
But yes you are correct that the sum of all the breakers can exceed the service in a normal panel because the main breaker is there to trip and protect the main service, etc.
Do they make 125 amp panels with enough circuits to handle your house? Seems like you might need a sub panel to handle all the circuits.
How big of a system are you thinking? NEC/AHJ might not be happy with such a small main breaker but what about putting a 100 amp main breaker in a 125 amp panel? This would be safe and I doubt your house will ever have above an 80 amp draw. I turned on literally every thing in my entire house and barely got over 50 amp at 240 volt.
I've just realized that I may have misinterpreted what my electrician told me or he made a mistake. He said I can have a 4kW system with the 125A panel. Thinking about it, per the NEC's 120% rule I can back feed 25A of solar to a 125A panel with 125A breajer which translates to a 6kW array on 240V. Putting in a 100A breaker on the same panel would give me a total of 50A of solar current which is a 12kW array. I was shooting for a 7.2kW system, so I might be ok with a 100A breaker. Am I missing something?
So the math is like this:
125 *1.2-125=25 amp breaker for solar
125*1.2-100=50 amp breaker for solar
So depending on what kind of inverters you are looking at you could go into a sub panel powered by 25 amp/50 amp breakers. If you went with Enphase M215 microinverters:
25*.8 (continuous load derate factor): 20 amps
20/.9 (enphase amp rating): 22 M215s
50*.8 (continuous load derate factor): 40 amps
40/.9 (enphase amp rating): 44 M215s
If you were to connect your M215s up to 250 watt panels that would get you:
22*250: 5,500 watts DC
44*250: 11,000 watts DC
Basically you can have up to 20/40 amps of inverter output and then can add additional solar capacity above that. So a 4,800 watt central inverter or two of them. Then you'd add additional DC capacity to account for the conversion loss, wire loss, soiling loss, panel degradation, etc.
Note that the M215s are limited to 17 on a 20 amp circuit so to get 22 you would need a sub panel with two circuits.