7.7kW LG/Enphase System in San Diego

[71SoCal]

Well- The M215 saturates at 225W where the M250 saturates at 250W.

I have one client with 260W Solarworld modules that saturate the M215 at 225W for 50% of the day.
Another system with M250 and SW270's barely saturates (Also 240 Az). SW280 will saturate the M250 at 180 Az.

At 28 inverters, it's an extra 700W of headroom.

You can install upto 15 M250's per trunk line, or 17 M215's. Since the system is 28 inverters nothing extra is required changing from M215 to M250 (i.e. vs a 34 invertor system - changing to M250 would need another set of trunk line / breakers, etc), so worth a deep dive, IMO.

It would be about $500 more to go to M250 (before federal credit). I ran the PVWatts calculator and from reading several threads, I'm under the impression that rarely, if at all, I would clip during the summer for maybe an hour-ish each day. I'm hoping someone will chime in with some data that validates/invalidates my hypothesis.

Thanks for bringing up the topic. I would definitely consider bumping up to M250's if it could be justified

[NVEnergyLLC]

saturation

Well- The M215 saturates at 225W where the M250 saturates at 250W.

I have one client with 260W Solarworld modules that saturate the M215 at 225W for 50% of the day.
Another system with M250 and SW270's barely saturates (Also 240 Az). SW280 will saturate the M250 at 180 Az.

At 28 inverters, it's an extra 700W of headroom.

You can install upto 15 M250's per trunk line, or 17 M215's. Since the system is 28 inverters nothing extra is required changing from M215 to M250 (i.e. vs a 34 invertor system - changing to M250 would need another set of trunk line / breakers, etc), so worth a deep dive, IMO.

[71SoCal]

I believe it's about $18 more per inverter. From what I've read, the 275w panels will almost never clip with the M215's. My azimuth is 240 degrees, so I don't anticipate pegging the M215 very often, if at all.

[logdin]

how much are you saving by going with m215's vs m250's, especially with 275w panels?

[71SoCal]

I’m moving forward with my PV system. I’m able to fit 28 LG275w panels on my largest roof plane.

I’m putting together my permit package now and wanted to get some feedback on my single line electrical plan. I know AHJ’s differ, but especially if anyone is familiar with the City of San Diego, any feedback would be appreciated.

Here’s what I’m putting in my single line:

Equipment

• 28 - LG 275w Modules
• 28 - Enphase M215 Inverters (wired in 2 strings of 14 each)
• 1 - AC Combiner box on the roof with disconnect.
• 1 - 40amp AC disconnect next to main service panel. (SDG&E RMA Device: Supply-Side Tap)
• Existing 200amp main service panel with center-fed breaker. (this is why I have the RMA device)

Wiring Details

• 2 separate wiring systems:

o Power Generation System: AC wires from inverters, combined in roof disconnect, run to ground ac disconnect in conduit. Wires will be #8 THWN-2 in ¾” EMT. (4 wires: H1, H2, N, G).
o Grounding System: Dedicated ground rod tied to #6 bare wire (special bonding requirements?). #6 wire is run in the ¾” EMT. Will pass through roof combiner box (should it bond here?) then bond via lugs to each rack segment and each inverter body (Enphase supports this, I believe). Modules will bond to racks with WEEBs. Rack segments will be bonded together. #6 picks it all up.

Wire Calcs

• Amp calcs per string: (14 x 0.9 x 1.25) = 15.75 amps.
• Combined strings: (15.75 x 2) = 31.5 amps. Use #8 THWN-2 for Power Gen System and 40 amp breaker in ground ac disconnect.
• #6 ground wire will be single strand.
• 5 wires total in ¾” conduit running up side of house, into attic, and out through flashing to AC combiner/disconnect box.

Am I missing anything? Thanks for taking a look…