Good video on PV grounding

[FilterGuy]

 

[timselectric]

Hopefully this will help people understand.
This is going to save me from explaining it over and over.

 

[FilterGuy]

BTW: One thing the video did not go into was talking about why NOT to do an auxiliary grounding electrode for the PV array.

 

[timselectric]

BTW: One thing the video did not go into was talking about why NOT to do an auxiliary grounding electrode for the PV array.

No, but he covers it in other videos.
If someone wants to know why.
It doesn't only pertain to solar installations.
It was an issue before solar got popular.

 

[FilterGuy]

 

[Zwy]

BTW: One thing the video did not go into was talking about why NOT to do an auxiliary grounding electrode for the PV array.

The steel pole 8.5 feet in the ground, wrapped in concrete. I'd use a plastic pole but they don't seem to make one that can handle it.

Yes, this does have a grounding electrode conductor from the PV array to the house grounding system.

 

[FilterGuy]

Yes, With ground-mounted arrays, it can be difficult to avoid a 2nd earth grounding point. In this situation, I run the EGC from the array directly to the main breaker box where the system grounding jumper goes to the grounding electrodes. This keeps the potential pulse away from all the solar electronics.

 

[FilterGuy]

Yes, With ground-mounted arrays, it can be difficult to avoid a 2nd earth grounding point. In this situation, I run the EGC from the array directly to the main breaker box where the system grounding jumper goes to the grounding electrodes. This keeps the potential pulse away from all the solar electronics.

BTW: The NEC makes a specific allowance for routing the EGC separately from the PV circuits. I suspect at least part of the reason for this is to allow the EGC to go directly to the common ground bus where the Grounding Jumper is.

 

[Robkh]

I have a 4000W ground mounted array >100 feet from the house. Even though NEC 690.47(A)(1) says that “the PV output circuit is the only connection to ground required for the PV system” do you recommend I still run 6AWG copper ground wire with my PV cables in a buried conduit to join with the earth ground bus bar at my house where the EG4 6000XP inverter resides?
I suspect that is the right thing to do to avoid potential differences as everything is connected to one earth ground.

 

[Zwy]

I have a 4000W ground mounted array >100 feet from the house. Even though NEC 690.47(A)(1) says that “the PV output circuit is the only connection to ground required for the PV system” do you recommend I still run 6AWG copper ground wire with my PV cables in a buried conduit to join with the earth ground bus bar at my house where the EG4 6000XP inverter resides?
I suspect that is the right thing to do to avoid potential differences as everything is connected to one earth ground.

You do not need 6AWG, it can be sized to the amps carried by the PV current carrying conductors.

You are required to run a ground wire from array to house grounding system. That is the only ground wire needed, no auxillary ground rod.

 

[AZ Solar Junkie]

Good one to bookmark for sure

 

[Robkh]

You do not need 6AWG, it can be sized to the amps carried by the PV current carrying conductors.

You are required to run a ground wire from array to house grounding system. That is the only ground wire needed, no auxillary ground rod.

Thanks good to know 6AWG is overkill. I will eventually have two ground mounted arrays, each delivering Vmp 310V PV array current 13A. What size copper do you recommend?

 

[Zwy]

Thanks good to know 6AWG is overkill. I will eventually have two ground mounted arrays, each delivering Vmp 310V PV array current 13A. What size copper do you recommend?

What size are the current carrying conductors? Usually one size down.

Exposed ground wires need to be 6AWG but once in a box or conduit it can be downsized.

I ran 10AWG to minimize voltage drop with a 420 foot run even though amperage is only about 12A. The ground wire is 10AWG, I just keep everything the same size usually. I could have used 12AWG.

 

[timselectric]

I ran 10AWG to minimize voltage drop with a 420 foot run even though amperage is only about 12A. The ground wire is 10AWG, I just keep everything the same size usually. I could have used 12AWG.

You could have used 14 AWG. But I would have also ran 10.

 

[Robkh]

One more question regarding NEC 690.47(A)(1) - most PV systems are functionally grounded rather than solidly grounded. Mike Holt says that for functionally grounded systems, the inverter equipment grounding conductor is connected to the grounded distribution equipment. This connection is used for the ground-fault protection and for equipment grounding of PV array.

Additional grounding of the PV system is permitted but not required. This seems to suggest that attaching PV array ground to earth ground is not required.

However it doesn’t seem a big deal for me to connect the ground wire from the PV array to the earth ground before the PV cables enter the house. Also any ground faults would go directly to earth-ground instead of coursing through the inverter to the earth grounded distribution system.

 

[timselectric]

Additional grounding of the PV system is permitted but not required. This seems to suggest that attaching PV array ground to earth ground is not required.

Or recommended.

However it doesn’t seem a big deal for me to connect the ground wire from the PV array to the earth ground before the PV cables enter the house. Also any ground faults would go directly to earth-ground instead of coursing through the inverter to the earth grounded distribution system.

Ground faults do not go to earth. They return to the source. (N/G bond)

 

[Robkh]

I forgot that the neutral ground bond clears the fault. My error. Thanks for clarifying Timselectric.

 

[edward4]

I am planning on direct burying my PV wires from my ground mount back to the inverter at my house. Should the ground wire be bare in the trench?

 

[Zwy]

I am planning on direct burying my PV wires from my ground mount back to the inverter at my house. Should the ground wire be bare in the trench?

What type of wire do you plan on using for direct burial?

I highly recommend using PVC conduit and one that is large enough you can add more wires later.

 

[timselectric]

I am planning on direct burying my PV wires from my ground mount back to the inverter at my house. Should the ground wire be bare in the trench?

I wouldn't use bare. But if your ground mount is made of metal posts in the earth, it really doesn't matter.

 

[edward4]

What type of wire do you plan on using for direct burial?

I highly recommend using PVC conduit and one that is large enough you can add more wires later.

I understand the recommendation but my array needs to be about 300ft from the inverter. Will be using XPLE direct burial rated wire.

 

[Zwy]

I understand the recommendation but my array needs to be about 300ft from the inverter. Will be using XPLE direct burial rated wire.

My array is 420 feet away and I'm glad I used conduit because I will be adding more wires this summer.

I've used XLPE direct burial for service cable. Over time I wished I had instead ran conduit. It's a tossup when it comes to price, XLPE normally runs about twice the cost of THWN. One needs to weigh the cost of conduit and serviceability.

One can cheat and use non perforated drainage tile, farmers around here use if all the time with XLPE wire inside when running from building to building. It beats digging up the whole yard when a problem occurs.

 

[edward4]

My array is 420 feet away and I'm glad I used conduit because I will be adding more wires this summer.

I've used XLPE direct burial for service cable. Over time I wished I had instead ran conduit. It's a tossup when it comes to price, XLPE normally runs about twice the cost of THWN. One needs to weigh the cost of conduit and serviceability.

One can cheat and use non perforated drainage tile, farmers around here use if all the time with XLPE wire inside when running from building to building. It beats digging up the whole yard when a problem occurs.

Do you know a good source for THWN? Home Improvement stores seem to be very expensive.

 

[Zwy]

Do you know a good source for THWN? Home Improvement stores seem to be very expensive.

I buy mine from Menards in 500 foot rolls with the 11% rebate. I've looked around but shipping wire gets costly too as it isn't light.

I picked up 3 sticks of 10 foot Type L copper the other night with a few bags of fittings. $170, copper certainly isn't getting cheaper. I did my 60 x 80 shop air lines back about 13 years ago in 1" Type L and it cost me about $3500 back then so it certainly is much higher. 10AWG THHN/THWN is $129 per 500 foot roll which is about what I paid 1.5 to 2 years years ago. That gets the 11% rebate so about $115 per 500 foot roll. I don't see copper coming down in price for some time, there is too much construction, solar, wind and other uses that keep demand high.