Enphase microinverter branch max circuit size?

[wwhitney]

Right, and while that diagram shows just one daisy chain of the EnGroovy (or whatever they call it) cable going to the junction box, you could have multiple daisy chains all going to the junction box, as long as you meet the count limit on microinverter output current per 20A OCPD.

Cheers, Wayne

 

[Solar Guy]

Well, if you (correctly) need a 20A OCPD per string of 11, and you have more than one of such strings, I think your J-box just turned into a combining panel.

 

[jsherwin]

Sorry guys - still not what I am asking. How about this... Enphase makes the q aggregator - where you can combine three strings - that device includes 20 amp fuses for each of the three strings going into the aggregator. Are those fuses required by code? or could I skip their device and use a power block in a junction box that takes me from the three to a single home run to the service panel?

 

[wwhitney]

Sorry guys - still not what I am asking. How about this... Enphase makes the q aggregator - where you can combine three strings - that device includes 20 amp fuses for each of the three strings going into the aggregator. Are those fuses required by code? or could I skip their device and use a power block in a junction box that takes me from the three to a single home run to the service panel?

Those fuses are required by the manufacturer's specs if you'd otherwise have more than 16A (continuous) worth of inverters on an OCPD. So in that sense they are at least required by 110.3(B).

Cheers, Wayne

 

[Solar Guy]

Endphase's "aggregator" is a combining panel with a monitor card. Each string has a 20A breaker, or a fuse. If you don't want to buy an aggregator, just buy a 240V 60A 6-space panel like the ones in a motel kitchenette and use that.
If you try to take, for instance, three strings of 10 micros and lug them together on a terminal strip, you essentially have 30 micros in parallel. That violates the product's installation manual. You would need a 55A backfeed breaker at the service panel and max-out that #8 Romex from the t-strip, but the PV pigtails and the micros themselves won't be protected.

 

[jaggedben]

Sorry guys - still not what I am asking. How about this... Enphase makes the q aggregator - where you can combine three strings - that device includes 20 amp fuses for each of the three strings going into the aggregator. Are those fuses required by code? or could I skip their device and use a power block in a junction box that takes me from the three to a single home run to the service panel?

The fuses are required by code.
Strictly, we can say that's because the manufacturer says so, and the code always requires you to follow manufacturer instructions. (110.3(B)). But even if the manufacturer were vague on this point, the code would still require the fuses, because the wire size used to connect the inverters requires overcurrent protection. 240 requires it on general and 705 lays out specific requirements for inverter outputs.

 

[jaggedben]

Endphase's "aggregator" is a combining panel with a monitor card. ...

The aggregator is a different product from the combiner. It's designed for roof, and still combines circuits, but doesn't have a monitoring unit and isn't a panel.

 

[Solar Guy]

Jagged Ben, you're right; I was thinking about the Enphase IQ unit which does have a monitor board and does combine parallel strings. But neither the IQ nor the aggregator is a "panel" in the sense that you cannot take a branch load off it with another breaker. I should not have called it a panel. But it is a solar circuit combining thingy with OCPDs.

 

[ggunn]

A string of microinverters is always connected in parallel. You can have as many on a string as the spec sheet allows--typically, as in the OP, the spec sheet listed a maximum 20A OCPD and that determines the maximum count.

Cheers, Wayne

The limit of 20A per microinverter circuit is dictated by the size of the conductors in the trunk cable.

 

[wwhitney]

The limit of 20A per microinverter circuit is dictated by the size of the conductors in the trunk cable.

Are you suggesting that if you made your own trunk cables with #10 AWG instead of #12 AWG, you'd be allowed to use 30A circuits for the microinverters? Despite the 20A limit being codified on the spec sheet?

Cheers, Wayne

 

[pv_n00b]

The limit of 20A per microinverter circuit is dictated by the size of the conductors in the trunk cable.

It's limited by Enphase to 20A. Put as big a conductor on it as you want, still needs to be protected at 20A.

 

[Solar Guy]

The Enphase IQ series of microinverters come with modular connectors and plug-and-play cabling that is no larger than #12AWG, so that limits things to 20A. You can't open the unit to change the wiring and still keep the UL listing, and you would probably break it trying to carve into the module anyway. Not to mention the labor cost.

 

[jaggedben]

Are you suggesting that if you made your own trunk cables with #10 AWG instead of #12 AWG, you'd be allowed to use 30A circuits for the microinverters? Despite the 20A limit being codified on the spec sheet?

Cheers, Wayne

You couldn't spec your own trunk cable size if the manufacturer's design allowed it, although I haven't seen one that does. There is one manufacturer with 10awg trunk cable that allows 24A per circuit. I think the point is that the manufacturer and 110.3(B) place constraints, while the code only requires an OCPD that protects the wire size used.

 

[ggunn]

We have used #10 cabling with Enphase micros for voltage drop, but we still are limited to 20A breakers by the Enphase specs..

 

[danmark2002]

Greetings all I have only ever installed a dozen or so microinverter systems, and always have used 20 amp branch circuits and 12/2 wire (perhaps also 10/2 for voltage drop).
I have a job where another electrician roughed in a nice beefy 8/2 romex for the 'future solar' and now that the future is here and the solar is being installed I put it on a 30A breaker, just because I had it in the van, then I got to thinking I have never used a circuit larger than 20 Amps so I looked over the enphase documentation figuring I would see something saying I need a 20 Amp circuit max but instead it says:
5 "Limits may vary. Refer to local requirements to define the number of microinverters per branch in your area."

In my area its pretty much just the NEC, Is there anything in the NEC that limits the microinverters branch circuit to 20 amps?
For this particular system its tiny only 3.7 kVA, but I was thinking of larger systems in the future.
Thanks in advance and happy friday

I just got Certified to install Enphase micro inverters. The max breaker you can use is 20 amp since the interconnect cables is 12 gauge. Enphase say max 20 amp so you have to follow their instructions. That does not mean you cannot oversize the wire for VOLTAGE RISE as they call it when working on solar. You can take their course and get certified for free. It is really informative

 

[pkhosravani]

Is there a safety, code, or other reason holding Enphase back from increasing the size of their Q-cable? I just saw that APsystem's has a 10awg trunk cable that installs on a 30A CB. Anyways, this tweak would certainly lead to increased install times and a reduction in materials. Thoughts?

 

[jaggedben]

Is there a safety, code, or other reason holding Enphase back from increasing the size of their Q-cable? I just saw that APsystem's has a 10awg trunk cable that installs on a 30A CB. Anyways, this tweak would certainly lead to increased install times and a reduction in materials. Thoughts?

I don't think there's a code or saftey reason. Back in the day they increased it from 14awg to 12awg. Increasing the size more would make the trunk cable more expensive. More inverters per branch might possibly cause more issues with voltage rise.

Also the cost benefit of going to 10awg is spotty; it benefits systems between 3.84kW AC and 5.67kW (AC rating), but adds cost to systems under 3.8kW or between 5.76kW and 7.68kW. So the difference may be marginal or a bit negative when aggregated across lots of systems, depending on the mix of systems in any sample set you look at. Probably for this reason there just isn't much impetus to change.

 

[pkhosravani]

Let me rebuttal to keep things interesting. Firstly, I can’t speak on voltage drop, but my best guess would be that it’s an equal concern no matter the wire size. Of course 10awg costs more, but in many situations you’ll be able to eliminate an entire circuit, that equals less overall wire in the system, which means less field installed connectors, less CBs, less Romex, etc. Heck why not keep the 12awg option and make a 8awg version on a 40amp CB. That’s the sweat spot for most homes with a 200a bus/main. With one 8awg branch circuit you’d eliminate the need for the IQ combiner and the required breakers, now you just need (1) BF CB…but this does create the problem of how to power the IQ gateway and where to install it.


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[shortcircuit2]

Many AHJs required a .58 temp derating factor

.58 in table 310.15(B)(1)?

So the AHJ's in your area have determined an ambient temperature of 150-158 degrees F?

I agree it is very hot on the roof due to solar radiation. What data is used to determine this ambient?

 

[danmark2002]

Greetings all I have only ever installed a dozen or so microinverter systems, and always have used 20 amp branch circuits and 12/2 wire (perhaps also 10/2 for voltage drop).
I have a job where another electrician roughed in a nice beefy 8/2 romex for the 'future solar' and now that the future is here and the solar is being installed I put it on a 30A breaker, just because I had it in the van, then I got to thinking I have never used a circuit larger than 20 Amps so I looked over the enphase documentation figuring I would see something saying I need a 20 Amp circuit max but instead it says:
5 "Limits may vary. Refer to local requirements to define the number of microinverters per branch in your area."

In my area its pretty much just the NEC, Is there anything in the NEC that limits the microinverters branch circuit to 20 amps?
For this particular system its tiny only 3.7 kVA, but I was thinking of larger systems in the future.
Thanks in advance and happy friday

I installed a system recently and in the documentation from enphase they do not consider anything else than the max current for a 12 gauge wire. If the inverter says max fuse 20 amp then that is the maximum you can use. However the code has several reduction factors you have to consider including voltage drop ( actually voltage rise ), Enphase show in there online course the max inverters you can add to each string to avoid raising the voltage too much. Wire closer than 1 1/2 inch to the roof ( you have to add 60 degree to temperature correction ), continuous power add 25 % are those I can just think of out of my head.