Location of AC Solar sub-panel

[bryankloos]

Hey Guys,

I'm curious what you think about housing the AC PV sub/combiner in the attic. This would allow me to combine all 5 sub arrays in the attic and run a single run of larger gauge wire to the AC disco and then to the line side connection. What are the pros/cons of doing this versus running the 5 sub-arrays down and then combining in the basement?

Thanks,

Bryan

[SunEagle]

It comes down to what your local inspector agrees to as well as meeting any safety codes that requires a easy access way to disconnect the power from the pv system. While it may cost you more it might be better to have the combiner box up on the roof close to the arrays.

[Eleceng1979]

As sun eagle said...consult your local inspector first... he/she has authority here and is the only one that matters. Most are good people that welcome conversations prior to inspections. You say 5 arrays but what is the panel count? If enphase you could combine panel strings to achieve maximum rated current/least amount of circuits. Your array grounding/bonding method/routing is not mentioned and needs considered.

Pros of pulling all down to basement... (assuming enphase micros)
1. You only need romex once trunk cable is in the attic/indoors x 5 circuits = easy and pretty cheap
2. New inverter sub panel closer to meter/supply side tap...in case of future expansion/ease of use, etc...
3. Simple and straight forward
4. You can't fall through a basement floor

Cons of pulling down to basement
1. More romex
2. Possible routing issues to attic

Pros of combining in the attic
1. Closer, using only enphase trunk cable to panel
2. Easier expansion

Cons of combining in attic
1. Could be problematic for inspections, untreated/non usable space/inaccessible, etc...
2. Larger wire/cable size to pull down to basement. It might be more costly vs smaller multiple cables
3. Temperature of circuit breakers, wiring, etc... not sure of your climate/location
4. You can fall through ceiling of area below

What I would do...
1. Set new subpanel in basement, feed to supply side tap
2. Run at least 1" conduit to attic if possible (not sure of your wire count/amperages/wire size) romex would suffice but you need multiple runs now.
3. Install a wire trough in attic to splice enphase cables to wires in conduit
4. Splice wire in trough with proper outdoor rated, sealed permenant crimps to prevent future issues due to thermal/moisture issues (attics are untreated air, that could have high humidity. No place for a power circuit with indoor rated, wire nuts and a bit of tape as protection)
5. Forget about attic wiring forever
6. Pull a spare circuit or two if any possibility of expansion
7. Terminate in basement where it's cooler so your beer doesn't get so hot
8. Place a fused disconnect beside meter/supply side tap box
9. Don't place supply tap in the meter base