Subpanel - it can minimize rewiring in the future if you expand, also subpanels can be a cheap way to adapt different wire sizes and ampacity. For instance, you could provision that disconnect to its full rating (let's call it 100A) (can be cost-efficient if you use Al SER or individual conductors) on feeder breaker, feeder wire, into a subpanel. And then have 30A branch circuits in the subpanel. It also reserves space on the wall for feeding in more circuits.
There's a bunch of typos on page 4
- you're not using enphase, so you don't have a Q cable. It's a 10/2 with ground TC-ER (tray cable, exposed run) for Hoymiles. They got this right in one part of the diagram
- 3/4" Romex Run - not a thing. Also #8 THWN - is this a local code compliance thing? If it is, everything has to be in conduit since 10/2 Romex with ground has #10 EGC.
- I think most places, it means Conduit. But they didn't specify the type.
- Ah, the #8 might be because you have 20A circuit but #10 AWG wire, and there's a rule that requires you to upsize EGC in cases vaguely like this
- Load center has 20A backfeed branch breaker, PV breaker is 20A. This is probably easier for reviewers to understand, but it's forcing you to have #8 EGC (if I remember that clause correctly)
Do you want the roof runs to be in Romex, or in conduit? If in Romex you need to address the EGC sizing issue. If you want it in conduit (allows switching to DC more readily, looks better? I used conduit for my microinverters. The conduit also can let you scale to more than 4 HM 1500 microinverters if you want to add more) then it doesn't matter since #8 EGC vs #10 EGC is marginal difference. Note that putting more than 1 #30 circuit in a conduit in a hot Texas attic may require enough CCC + temp derating that you have to go down to 3 HM-1500 per branch circuit.
Single cable -> 4 HM1500
Conduit: 3, 6, or 9 (3 per circuit)
Or increase to #8 circuit (but this will not fit 3 circuits in 3/4 conduit, you can fit 2 circuits which is 8 HM-1500)
Random points about the design
- Looks like this rail-less is more roof penetrations than a rail system.
- Looks like you could easily put WAY more panels on this roof plane. When I installed with EZ solar on 4 roof planes, I found that the most efficient install were when I slapped down bunch of panels for a single junction box. That said, putting them in two columns is efficient since you only have to find 4 rafters.
- How much is it to go up to a 100A VLLD, in case you expand the system later? (This could raise some questions during review since it's oversized, but you could probably make up some excuses like preferring the physical design or wanting the headroom).
