I have an inspector in CT that is looking to have our breakers inside the envoy that protect each string be sized to the amount of panels that the string has. We have never put anything but 2p20a breakers to land our strings and only info I can find is that it’s a 20a max. He said the code article is in 690. I can again find nothing saying backing it up. I’m waiting for him to post the issue in the permit portal so I can dive deeper into what he is saying. Anyone have any input on this?
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Envoy breaker sizing
- Thread starter Tlehane3
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Carultch
Senior Member
- Location
- Massachusetts
There is no requirement to use a lower-than-20A breakers on Enphase branch circuits, just because you have fewer inverters on them. Each inverter branch is meant for a 20A circuit, whether the current adds up to 16A (the maximum allowed on a 20A circuit), or considerably less.
Suppose the current among the microinverters on the branch in question add up to 12A. This means the breaker size could be as low as 15A, but it doesn't necessarily need to be 15A. The microinverter cabling uses #12 Cu wiring, and is protected by the 20A circuit either way. If an individual microinverter can be on a 20A breaker for the largest circuit in your system, it is no issue to be on a 20A circuit on an underloaded branch (provided the circuit uses 20A worth of wiring, of course).
Suppose the current among the microinverters on the branch in question add up to 12A. This means the breaker size could be as low as 15A, but it doesn't necessarily need to be 15A. The microinverter cabling uses #12 Cu wiring, and is protected by the 20A circuit either way. If an individual microinverter can be on a 20A breaker for the largest circuit in your system, it is no issue to be on a 20A circuit on an underloaded branch (provided the circuit uses 20A worth of wiring, of course).
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
The inspector is wrong. Good luck.
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
<hot button alert>
We have an inspector here who takes the same position; it's a real pain. The NEC clearly prescribes the minimum OCPD for all parts of a PV system on the AC side. As long as your conductors are adequately sized you can within reason make your OCPD rating as high as you wish*. The OCPD on the AC side is there to limit the feeding of a fault from the utility side; it has nothing whatsoever to do with the output current capacity of the inverter(s). But as a professional in the PV industry you know all that; an inspector who takes the position you describe is ignorant of PV system functionality and basic electrical theory.
I feel your pain. Does the inspector have a superior in his organization who understands how electricity works? If so appeal to him for a correction to his inspector's ignorant position. We are not so lucky.
*Yes, I know that some inverters specify a maximum AC OCPD, but it is always much higher than the maximum output current from the inverter and has nothing to do with this issue.
We have an inspector here who takes the same position; it's a real pain. The NEC clearly prescribes the minimum OCPD for all parts of a PV system on the AC side. As long as your conductors are adequately sized you can within reason make your OCPD rating as high as you wish*. The OCPD on the AC side is there to limit the feeding of a fault from the utility side; it has nothing whatsoever to do with the output current capacity of the inverter(s). But as a professional in the PV industry you know all that; an inspector who takes the position you describe is ignorant of PV system functionality and basic electrical theory.
I feel your pain. Does the inspector have a superior in his organization who understands how electricity works? If so appeal to him for a correction to his inspector's ignorant position. We are not so lucky.
*Yes, I know that some inverters specify a maximum AC OCPD, but it is always much higher than the maximum output current from the inverter and has nothing to do with this issue.
farmantenna
Senior Member
- Location
- mass
their combiner box with integral Envoy, I believe comes with the 20 amp CBs
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