We are adding more panels to an existing system. Currently there are (4) inverters, max ac output of 35a each. The MSP is 1200a, 208v. Is it allowable to add another inverter and feed the MSP with a second backfed breaker? The new inverter would have a max output of 60a
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2 systems, 1 MSP
- Thread starter Smarsh83
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jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
It's allowable to have two PV breakers in the MSP if other rules are met.
Your post is a little light on detail, but assuming you mean the MSP is 1200A with 1200A main breaker, and all the inverters are 3 phase, you meet the 120% rule if you can put both PV breakers at the opposite end. Or you can use the 'sum of all breakers' if the load breakers add up to no more than 1000A.
Your post is a little light on detail, but assuming you mean the MSP is 1200A with 1200A main breaker, and all the inverters are 3 phase, you meet the 120% rule if you can put both PV breakers at the opposite end. Or you can use the 'sum of all breakers' if the load breakers add up to no more than 1000A.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
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- Consulting Electrical Engineer - Photovoltaic Systems
Also, some AHJs will not allow more than one PV system interconnection point on a service irrespective of other compliances. Ask them as well as us.
Correct, the MSP and main breaker are both 1200a. The existing 4 inverter are 3 wire single phase. The new inverter we would like to add is 3ph 208v. And I have room for both PV breakers at the opposite end of the meterIt's allowable to have two PV breakers in the MSP if other rules are met.
Your post is a little light on detail, but assuming you mean the MSP is 1200A with 1200A main breaker, and all the inverters are 3 phase, you meet the 120% rule if you can put both PV breakers at the opposite end. Or you can use the 'sum of all breakers' if the load breakers add up to no more than 1000A.
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
So you have unbalanced line currents on the existing system, that makes it more complicated.
Are the existing inverters combined before going to the MSP? The 35A and 60A are before the 125% factor is added?
Regardless, there is no hard rule in the NEC against having two PV breakers in a panel, although individual AHJs might have local rules like ggunn mentioned.
Are the existing inverters combined before going to the MSP? The 35A and 60A are before the 125% factor is added?
Regardless, there is no hard rule in the NEC against having two PV breakers in a panel, although individual AHJs might have local rules like ggunn mentioned.
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