Can I install a 120 volt receptical at my solar system racking?

[Murby]

What you are missing is that the earlier versions of the NEC assume that you could someday have either a fault or a newly installed load attached somewhere along the length of the feeder which would take power from both ends and therefore would not be protected by OCPD at either end.
This unrealistic assumption was effectively rejected in the 2017 code version.

Wow.. did it really take them until 2017 to figure out it was unrealistic? LOL..

[bcroe]

I'm not sure how the code is going to treat this, but if you have breakers on every section of wire and outlet
protecting them, you can hardly go wrong. Having outlets far from buildings is quite useful for temp setups;
I used mine this week for some lights to work on the PV array in the dark. 3 outlets spread over 200' with
GFIs and a 20A breaker, bring temp power over the last 400' of my lot. Bruce Roe

Outlet.png

[sensij]

Edit: Inetdog beat me to it...

Am I missing something?

As written in an older Mike Holt thread:

The conductors between the main panel and the subpanel form an interesting area for discussion when PV backfeed is involved. Some inspectors assume that some day someone might tap a load to the feeder somewhere between the main and the sub, thus creating a situation where the feeder could be fed from both ends and overloaded. This, in their minds, justifies applying the 120% rule to the feeder conductors.

Others argue (with logic but not necessarily literal code support) that if there are no taps on the feeder now you can calculate on the basis that there will never be a load in the middle of the feeder. So the current in the feeder cannot exceed the larger of the PV output current or the feeder breaker current.

[inetdog]

I'm not sure how it would make any difference.. If there's a 70 amp breaker, the wire can't pass more than 70 amps in any direction either coming from the main panel or being back fed from the sub panel.

Even if someone hooked up a generator to the sub panel, there's no way to back feed more than 70 amps through that 4ga wire because it has a 70amp breaker on it. Now you could hook up a generator and feed much higher amperage into the sub-panel and then into the various breakers and connected loads, but you could do that with any panel.. and so long as each circuit has a breaker, the amperage can't exceed what the wire can carry.

Am I missing something?

What you are missing is that the earlier versions of the NEC assume that you could someday have either a fault or a newly installed load attached somewhere along the length of the feeder which would take power from both ends and therefore would not be protected by OCPD at either end.
This unrealistic assumption was effectively rejected in the 2017 code version.

[Murby]

I assume that both the 70A will be at the opposite end of feeder for it's busbar, as well as the 30A will be at the far end from the lugs on it's busbar

I *think* there's some weirdness in one of the versions of NEC that it could be interpreted that you need to use the 70A in your 120% rule calculations on the main panel.
1> figure out which version of NEC you're on.
2> draw up your plans exactly as they'll be installed and talk to the plan inspector to make sure what you're planning is fine. (logically it's obvious you'd only have 30A backfeed at the main panel. But I could see a plan inspector going with a theory that the bigger breaker could theoretically allow someone in the future to add more backfeed at the remote panel without them tripping that 70A breaker.)

I'm not sure how it would make any difference.. If there's a 70 amp breaker, the wire can't pass more than 70 amps in any direction either coming from the main panel or being back fed from the sub panel.

Even if someone hooked up a generator to the sub panel, there's no way to back feed more than 70 amps through that 4ga wire because it has a 70amp breaker on it. Now you could hook up a generator and feed much higher amperage into the sub-panel and then into the various breakers and connected loads, but you could do that with any panel.. and so long as each circuit has a breaker, the amperage can't exceed what the wire can carry.

Am I missing something?

[sensij]

I *think* there's some weirdness in one of the versions of NEC that it could be interpreted that you need to use the 70A in your 120% rule calculations on the main panel.

The calculation of the 120% rule in recent cycles is pretty clear that the OCPD size at the inverter is used for all busbar calculations, and was replaced with using 125% of the inverter's rated output current in 2014 NEC.

The weirdness that I'm aware of relates to sizing the feeder to the sub panel. There are cycles and interpretations that would require it to carry both the 70 A from the main panel and the 30 A from the PV, or 100 A total.

[foo1bar]

My plan is to install an 8 place (16 circuit) 125amp sub panel with main lugs (NOT Main Breaker). It will be fed by a 4ga/3wire +grnd direct burial cable. The breaker in my home will be 70 amps and the 4ga will feed directly to the lugs with an isolated neutral wire. From there, I will install a 30 amp (2pole) breaker to the inverter, then single pole 15 amp (GFCI) breaker to an outlet and a 10amp breaker to a auxiliary yard light.

I will be sure that the inverter feeds the sub panel at the opposite end of buss bar from the main lugs. The inverter is 6kw.

Does that sound like a good plan?

I assume that both the 70A will be at the opposite end of feeder for it's busbar, as well as the 30A will be at the far end from the lugs on it's busbar

I *think* there's some weirdness in one of the versions of NEC that it could be interpreted that you need to use the 70A in your 120% rule calculations on the main panel.
1> figure out which version of NEC you're on.
2> draw up your plans exactly as they'll be installed and talk to the plan inspector to make sure what you're planning is fine. (logically it's obvious you'd only have 30A backfeed at the main panel. But I could see a plan inspector going with a theory that the bigger breaker could theoretically allow someone in the future to add more backfeed at the remote panel without them tripping that 70A breaker.)

[Murby]

Ok. To be clear you are installing a remote power panel that is connected to your main house panel. At the remote panel you are backfeeding the output of the solar inverter as well as feeding an outdoor receptacle.

Just make sure you follow the code when you size your remote panel including the breaker feeding it and the cable from the main panel.

My plan is to install an 8 place (16 circuit) 125amp sub panel with main lugs (NOT Main Breaker). It will be fed by a 4ga/3wire +grnd direct burial cable. The breaker in my home will be 70 amps and the 4ga will feed directly to the lugs with an isolated neutral wire. From there, I will install a 30 amp (2pole) breaker to the inverter, then single pole 15 amp (GFCI) breaker to an outlet and a 10amp breaker to a auxiliary yard light.

I will be sure that the inverter feeds the sub panel at the opposite end of buss bar from the main lugs. The inverter is 6kw.

Does that sound like a good plan?

[SunEagle]

The inverter is outdoors.

I've decided to do away with the junction box and distribution block and just install an 8 place sub-panel.. Its actually cheaper than having to purchase the box and distribution block and all the other garbage.

Ok. To be clear you are installing a remote power panel that is connected to your main house panel. At the remote panel you are backfeeding the output of the solar inverter as well as feeding an outdoor receptacle.

Just make sure you follow the code when you size your remote panel including the breaker feeding it and the cable from the main panel.

[Murby]

The inverter is outdoors.

I've decided to do away with the junction box and distribution block and just install an 8 place sub-panel.. Its actually cheaper than having to purchase the box and distribution block and all the other garbage.

[Mike90250]

Is the inverter outside, at the array ?
Anyway, you can't mix DC and AC wires in the same conduit.
But you can run a feed from your main panel to the yard.

[SunEagle]

Absolutely you can. It just needs to be code compliant. Run a 3-wire circuit from your main beaker panel through a fuse. Or better yet find a circuit on your homes exterior walls and tap it. Any home built recently will have one dedicated circuit by the Air Conditioning compressor, Just tap it and be sure to use a GFCI recept.

I believe the OP just wanted to tap the output of the inverter at the inverter for that receptacle.

Can you basically wire the output of the inverter to the house panel as well as to a dedicated receptacle that is protected with an OC device?

I wasn't sure but even if it is ok per the NEC is might not be ok with the AHJ.

[Sunking]

Absolutely you can. It just needs to be code compliant. Run a 3-wire circuit from your main beaker panel through a fuse. Or better yet find a circuit on your homes exterior walls and tap it. Any home built recently will have one dedicated circuit by the Air Conditioning compressor, Just tap it and be sure to use a GFCI recept.

[SunEagle]

I doubt anyone would fault you for taking a metal punch and putting the hole size you need at
the position you need it, as happens here. Bruce Roe

He is probably referring to the wire termination on the inverter not being big enough to accept that #4 wire.

[bcroe]

since the 4ga cable is far too large to run directly into the SMA inverter's 3/4 conduit
openings, I have to install a 12x12 inch square PVC junction box.

I doubt anyone would fault you for taking a metal punch and putting the hole size you need at
the position you need it, as happens here. Bruce Roe