Multiple PV interconnections points on one service.

[pkhosravani]

Has anyone interconnected enphase in two different locations on one electric service? Like one in the main panel and one in the sub panel in the detached garage that is 50ish feet away? I believe the NEC is silent on the number of interconnections on one service, so long as you maintain the 120% rule, which I will. One major concern is whether I need an extra gateway/envoy or will the PLC be strong enough to capture the micros on the detached garage sub panel. (No other solar in the neighborhood.) Trenching in the yard will be very expensive in this situation.


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[pkhosravani]

Red dot on the main house is where the meter and exterior main service panel & disco is located and the red dot on the detached garage is where the sub panel is located.


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[ggunn]

Has anyone interconnected enphase in two different locations on one electric service? Like one in the main panel and one in the sub panel in the detached garage that is 50ish feet away? I believe the NEC is silent on the number of interconnections on one service, so long as you maintain the 120% rule, which I will.

There is nothing in the NEC which would prohibit this arrangement, although some AHJs will not allow it.

A point that some seem to miss is that in a situation like you describe, 705.12 must be complied with in the main panel as well as in the sub panel. If the sub panel is energized through a breaker in the main panel, the PV current into the sub panel also counts toward the maximum allowed in the main panel along with whatever is connected in the main. The sub panel breaker must be at the opposite end of the bus from the utility feed and the PV interconnection breaker in the main must be adjacent to it (no loads between them).

 

[jaggedben]

I've done this sort of thing several times. But our main local utility doesn't require a PV disconnect for single phase services 320A or under, so that helps.

You probably won't need a separate gateway/envoy but you might want to budget for it just in case. There's really no way to find out ahead of time.

 

[pkhosravani]

I forgot the fact that the Enphase gateways have production CT's for the solar. So if I only used only one gateway and the included P-CTs to just monitor the main house PV, I would lose out on the production of the PV on the detached garage. Now I also heard that the gateway allows for an additional set of PV production CTs to be installed on it, so couldn't I technically run a shielded communication wire like 6" deep hand-dug, direct burial between the house and garage to capture the PV at the detached garage? Which is less than 60-feet distance. Otherwise, I would need an additional gateway out at the detached garage and hope that the home Wifi reaches it. Now if the Wifi is weak, couldn't I use some PLC wall adapters (Enphase EN-EPLC-01 Powerline Carrier for Envoy - Pack Of 2) install one on an outlet in the detached garage, then another in the house next to their internet router?

 

[jaggedben]

If it’s only solar (no energy storage) you can set the system display to use microinverter data for production and then not having all production go through the production CT doesn't matter that much. You lose some precision if the PLC is bad, but it might be worth the money saved.

Enphase does not support extended or paralleling production CTs. Although, it might work decently enough, I suspect they are just worried about the accuracy standard being met. (That is, if the data is just for the customer benefit then probably who cares, but it it's being used for SREC credits or something then someone might have a bigger issue with it.)

(If you have energy storage then the production CT is a bigger issue. But I've at least one system where the solar on the outlying building is just missed for that purpose. It works okay because those batteries are mainly there for backup.)