Solar PV earthing - cable size?

[sdold]

If the ground cable is unprotected, it must be at least 6awg. If you run it in conduit, it can be as small as the power wires coming off of the array.
The house service cable size has nothing to do with the array ground, unless the power company decided the service wires could fall onto the array.

I think the OP is asking about the GEC, what you describe sounds like the equipment bonding conductor which is sized per 250.122.

[somawheels]

That is only one function. The main purpose is to protect you from the utility primary to secondary faults.

How does Utility power get to the solar panel frames?

[somawheels]

I've seen a many websites say otherwise. some also say Lightning strikes some distance away can damage your equipment and this is a reason to earth the PV frame.

[emartin00]

I see, thank-you for that explanation.
However, I don't understand why the amps for the house affects the thickness the earthing cable for the solar panel frames.
I thought the main reason for earthing PV metal frames, is to prevent lightning strikes.

Grounding the PV array has NOTHING to do with lightning. If you get a direct strike, it will still blow something up.
Grounding the array is done to protect the equipment and personnel from shock. The ground wire provides a short circuit path that would blow the fuse and stop power from flowing.

If the ground cable is unprotected, it must be at least 6awg. If you run it in conduit, it can be as small as the power wires coming off of the array.
The house service cable size has nothing to do with the array ground, unless the power company decided the service wires could fall onto the array.

[Sunking]

I see, thank-you for that explanation.
However, I don't understand why the amps for the house affects the thickness the earthing cable for the solar panel frames.
I thought the main reason for earthing PV metal frames, is to prevent lightning strikes.

That is only one function. The main purpose is to protect you from the utility primary to secondary faults.

[SunEagle]

I see, thank-you for that explanation.
However, I don't understand why the amps for the house affects the thickness the earthing cable for the solar panel frames.
I thought the main reason for earthing PV metal frames, is to prevent lightning strikes.

It comes down to meeting the National Electric Code for Grounding conductor sizes based on service conductor sizes.

Sometimes going with a wire size a little bigger will get the AHJ to pass the inspection quicker then going with a wire size that just meets code.

[somawheels]

I see, thank-you for that explanation.
However, I don't understand why the amps for the house affects the thickness the earthing cable for the solar panel frames.
I thought the main reason for earthing PV metal frames, is to prevent lightning strikes.

[Sunking]

No questions asked # 4 AWG solid bare tinned copper. 6 AWG may fail inspection. Codes specify minimums, and for a GEC depends on the size of the Service conductors entering the facility. NEC table 250.66 dictates the minimum and goes like this for Copper

#8 AWG for up to a #2 AWG Service (50 to 100-Amp)
#6 AWG for up to 2/0 AWG Service (50 to 150-Amps)
#4 AWG for up to 3/0 AWG Service ( 50 to 300 Amps)

Use a 4 AWG and you get no questions unless your house has a 300 amp or more service. If you have a service of 300 amps or more, you are the top 1% income earners and don't give a crap. Let the hired help worry about it and take the responsibility.

Here is how electricians do grounding. Drive 2 Rods in the ground, connect them with #4 AWG, collect a check, and call it a day. They are not going to bother carrying #8 or #6 AWG on the truck when 4 fits everything and is what the Inspector is looking for. If he sees something smaller, he ask questions.

[DaveDE2]

Usually awg 6 solid copper.

[somawheels]

What wire size should I use when earthing my solar panel frame?
The cable run to the house' earth rod would be 20m away.