Solar Array Conduit - Seeking Advice

[timselectric]

Follow up question:

A few of you mentioned a ground wire in the conduit from array to inverters.

1) Should I have a ground wire in the array conduit?

2) If yes, what gauge, and what do i connect it to in the inverter area?

thx

Yes, a ground is required.
12 gauge would be sufficient. But I would make it 10 gauge.
It would connect to the solar panel frames and any metal racking.
At the house end, it connects to the rest of your grounding system. (Inverter, loads panel, and whatever else you have)

 

[ChrisG]

Yes, a ground is required.
12 gauge would be sufficient. But I would make it 10 gauge.
It would connect to the solar panel frames and any metal racking.
At the house end, it connects to the rest of your grounding system. (Inverter, loads panel, and whatever else you have)

@timselectric for a ground mount array you can’t just ground (earth) it at the array location?

 

[Zapper77]

@timselectric for a ground mount array you can’t just ground (earth) it at the array location?

Technically no if you follow current NEC. What's your ground array structure made out of?

 

[ChrisG]

Technically no if you follow current NEC. What's your ground array structure made out of?

It’s for testing purposes now and made out of wood, just 4 - 400w REC panels. The end state will be metal with 20 panels.

 

[niktak11]

@timselectric for a ground mount array you can’t just ground (earth) it at the array location?

I only grounded at the array location. Nothing in my system uses the PV ground to detect a fault though.

 

[timselectric]

@timselectric for a ground mount array you can’t just ground (earth) it at the array location?

That's called an auxiliary ground rod.
While they are allowed, but not required. (And not recommended by me)
They don't take the place of the required equipment grounding conductor.

 

[timselectric]

I only grounded at the array location. Nothing in my system uses the PV ground to detect a fault though.

It's not a "PV ground".
It's a required equipment grounding conductor.
It's purpose is to keep exposed conductive (metal) parts safe to touch.
If your system includes an AIO. It's very likely that there is AC voltage present on the PV wires.
If one of the solar panels fails to insulate from the frame. This could create a touch Hazzard, if not properly grounded.

 

[niktak11]

It's not a "PV ground".
It's a required equipment grounding conductor.
It's purpose is to keep exposed conductive (metal) parts safe to touch.
If your system includes an AIO. It's very likely that there is AC voltage present on the PV wires.
If one of the solar panels fails to insulate from the frame. This could create a touch Hazzard, if not properly grounded.

My array frames are grounded, just not to the house.

 

[Hedges]

My array frames are grounded, just not to the house.

Then they could represent a shock hazard.

A fault could cause PV frames to carry PV voltage. If you touch them you may complete a circuit to the earth (depending what inverter end does with the wires).
Even if the mount is grounded e.g. with a ground rod, there could be a potential difference between it and other parts of the earth due to current flow. Resistance of grounding is expected to be around 25 ohms. With 7A from a string, there could be 175V between certain points of the earth. I'm not sure the voltage gradient in earth under those conditions as current spreads out. With neither ground rod nor ground wire, then shock hazard would be expected if a fault occurred.

Having wire between array and equipment ensures they are at the same voltage, by carrying current between them. Then only an additional connection to earth (like a downed power line) would cause current through the earth. Faults to frame would not.

 

[timselectric]

My array frames are grounded, just not to the house.

That's earthed, not grounded.
They are two different things.

 

[timselectric]

My array frames are grounded, just not to the house.

If the solar panels fail to insulate from the frame.
Now the surrounding earth can be a Hazzard.

 

[zanydroid]

Not sure if this has been mentioned, but spare conductors need to be factored into current carrying conductor derating since NEC2014.

If the metal parts of the array are not grounded in a fashion consistent with what the ground fault detection on your SCC or inverter is designed to work with... ... ... I dunno about that. And if you're not sure how the GFP works I think it's best to bond it the way code says you should, because that's what the GFP was designed/listed to work properly with.

 

[niktak11]

Not sure if this has been mentioned, but spare conductors need to be factored into current carrying conductor derating since NEC2014.

If the metal parts of the array are not grounded in a fashion consistent with what the ground fault detection on your SCC or inverter is designed to work with... ... ... I dunno about that. And if you're not sure how the GFP works I think it's best to bond it the way code says you should, because that's what the GFP was designed/listed to work properly with.

From what I understand, sol-arks so not use ground at all for the PV arc fault detection. And the manual even says not to connect a ground wire from the PV frames to the solark's ground.

 

[zanydroid]

From what I understand, sol-arks so not use ground at all for the PV arc fault detection. And the manual even says not to connect a ground wire from the PV frames to the solark's ground.

I don't think arc fault will trigger in all ground fault conditions. I'm referring to Ground Fault Detector.

Have you reached out to SolArk support to get an explanation?

 

[zanydroid]

There's definitely a GFDI and GFCI circuit in the Solark 12K (I pulled out the manual to have a quick look), so the ground has to be handled in a way that's compatible with it.

 

[niktak11]

There's definitely a GFDI and GFCI circuit in the Solark 12K (I pulled out the manual to have a quick look), so the ground has to be handled in a way that's compatible with it.

You're right I just saw that there's an error code corresponding to a PV ground fault in the 15k manual

 

[zanydroid]

I don't really understand the full picture but I think there is a tradeoff between lightning strike protection and having a EGC path back to where the equipment is so that the ground fault can be detected/handled.

Maybe there's a way to do ground fault detection with a separate box, in a way that is more strongly isolated from the inverter & batteries, and then you can compromise less.

 

[timselectric]

Electrical grounding and lighting protection are two different systems. One should never be used for the purpose of the other.

 

[zanydroid]

I'm not sure that accurately represents how people think about it.

I think when people decide to not bond the array back to the house, they're sort of deciding that lightning protection is more important than grounding to spec (& not accidentally breaking safety mechanisms).

Curious how ground fault detection with GFDI breaker tripping on leakage compares to monitoring for a voltage difference between system ground and a wire bonded to the array frame, assuming that checking voltage that way can be done in a better isolated way than GFDI.

 

[timselectric]

I couldn't care less about how people think about it.
I only care that nobody gets hurt or killed.
Which is the purpose of grounding.