New Homes Solar ROMEX/NM-B + ground sizing

[Solarsince05]

Good Morning Solar Pros,

I am working on standardizing our new homes process across the board and one point I am trying to simplify for our teams is the electrical rough-in portion. Currently we are using all Enphase, running 10/2 from the j-box just below our array to the combiner and 10/3 from combiner to the main service. Also with that romex run is a seperate ground wire typically #8 stranded (sometimes bare if we let the rookie stock the truck), that we staple alongside the NM-B. After looking at cost vs labor, I had the thought to upsize the Romex to 8/2 and 8/3 so we could avoid having to run a separate ground wire. The issue I am running in to is that everything over #10 NM-B starts to downsize the ground. IE: 8/3 has a #10 ground.

I've called a few of our outside suppliers and Southwire directly. After getting kicked around between quite a few different people that had no idea what I was asking I decided to continue my search here. Does anyone make a #8 NM-B type wire that has the same size ground? Alternatively is there a better way that I have not thought of?

Thanks in advance.

 

[suemarkp]

Most likely no. The equipment ground conductor for circuits sized from 30 to 60 amps only needs to be #10, so that is what you get in a 10-3, 8-3, or 6-3 cable. If you need an odd sized ground, run a flex conduit (LFNC-B if outside or FMC if inside) and pull the size wires you want. Because it is a conduit you are bend limited, so talk to your electricians how they feel about installing a conduit system versus a cable. This may cost more than what you do now, so you may need to determine if the standardization -vs- cost is worth it.

 

[SceneryDriver]

Good Morning Solar Pros,

I am working on standardizing our new homes process across the board and one point I am trying to simplify for our teams is the electrical rough-in portion. Currently we are using all Enphase, running 10/2 from the j-box just below our array to the combiner and 10/3 from combiner to the main service. Also with that romex run is a seperate ground wire typically #8 stranded (sometimes bare if we let the rookie stock the truck), that we staple alongside the NM-B. After looking at cost vs labor, I had the thought to upsize the Romex to 8/2 and 8/3 so we could avoid having to run a separate ground wire. The issue I am running in to is that everything over #10 NM-B starts to downsize the ground. IE: 8/3 has a #10 ground.

I've called a few of our outside suppliers and Southwire directly. After getting kicked around between quite a few different people that had no idea what I was asking I decided to continue my search here. Does anyone make a #8 NM-B type wire that has the same size ground? Alternatively is there a better way that I have not thought of?

Thanks in advance.

I think you'll find that NM-B and even Tray cable start to downsize their grounds when the phase conductors get larger than #10.

Possible options:
Can you install conduit instead? You can pull exactly what you need.

Buy 8/3 NM-B cable, and remark the third conductor as a ground.

Have a custom cable made. That's not as crazy as it sounds. I'm having custom cable made right now by TPC Wire and Cable, and they're beating the pants off the price I was getting for a commensurate product from my Belden distributor. I'm getting the cable from TPC with a Type TC rating as well, and the Belden cable didn't have that.



SceneryDriver

 

[petersonra]

I don't believe code allows you to run the ground wire for a circuit in romex outside of the cable.

 

[JoeNorm]

Why are you running a separate ground? And Why are you running 10/2 from the array unless it is a longer run? 12/2 or 12/4 usually works.

 

[don_resqcapt19]

I don't believe code allows you to run the ground wire for a circuit in romex outside of the cable.

Yes, an external EGC would be a violation of 300.3(B).

 

[SceneryDriver]

Yes, an external EGC would be a violation of 300.3(B).

Maybe the OP's using the single green wire to bond the array racking to the grounding system, and the EGC in the Romex is the grounding conductor for the circuit itself?? I'd have to think about that and dig a little to see if that was OK. Thoughts?

It would still have to be a #4 or larger conductor to be run by itself, yes?


SceneryDriver

 

[jaggedben]

I suspect the OP believes that a GEC is necessary for the array. This is no longer true as of the 2017 NEC, but maybe they are trying to standardize across multiple states on different cycles of the code.

 

[petersonra]

I suspect the OP believes that a GEC is necessary for the array. This is no longer true as of the 2017 NEC, but maybe they are trying to standardize across multiple states on different cycles of the code.

I don't know. The OP mentioned ground wire not EGC or GEC. It is hard to know what he is up to. Where would you ever be able to run a #8 GEC anyway just stapled along a run of NM?

 

[jaggedben]

I don't know. The OP mentioned ground wire not EGC or GEC. It is hard to know what he is up to. Where would you ever be able to run a #8 GEC anyway just stapled along a run of NM?

Yeah I know, code would require #6, but I saw #8 done a lot in solar back several years ago, and I guess it just didn't get called that much by inspectors. Whether 8 or 6 this used to be pretty common in solar when everyone thought solar arrays needed GECs. Nowadays not so much unless you're still stuck on the 2014 or 2008 code.

 

[Carultch]

Where would you ever be able to run a #8 GEC anyway just stapled along a run of NM?

Inside a raceway, you could use a #8 GEC. External to a raceway, it would be a #6.