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Running a separate ground with metal-clad cable


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Any of you knowledgeable and helpful electricians know if running a #8 groundwire "zip-tied" to an MC cable #12 thru my attic is to code? It will be from a junction box on the garage siding (where PVC conduit will be led into) thru my attic and garage wall to connect to the back of a fused Disconnect (for a pv system) and then to my main 100 amp breaker. I'm told i need at least a #8 groundwire. Also, when running it along with the MC cable, I would need separate connectors for this groundwire to j-box and disconnect? Any opinions are appreciated, Akoni

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Any of you knowledgeable and helpful electricians know if running a #8 groundwire "zip-tied" to an MC cable #12 thru my attic is to code?

I don't know what you mean by "groundwire." If this is an equipment grounding conductor, it's got to be part of the cable -- inside it. You can't run a separate equipment grounding wire outside of the cable per 300.3(B). So, if it's an equipment grounding wire, buy the correct cable and don't try to cobble the circuit together.

If this is a grounding electrode conductor, there are several concerns:

1. You can't support it off of the MC cable. Cables can't be used to support anything other than themselves per 300.11©. It should be independently supported.

2. Use Table 250.66 to size the grounding electrode conductor. However, regardless of the size that you come up with, remember that, if the grounding electrode conductor is smaller than #6, it has to be run in conduit. If it's #6 or #4, it might still have to be run in conduit, depending on how it will be installed and whether or not it will be exposed to physical damage. Read all about it in 250.64(B). For your purposes, I suspect that you're going to need a #6 wire run on a running board through the attic.

It will be from a junction box on the garage siding (where PVC conduit will be led into) thru my attic and garage wall to connect to the back of a fused Disconnect (for a pv system) and then to my main 100 amp breaker. I'm told i need at least a #8 groundwire. Also, when running it along with the MC cable, I would need separate connectors for this groundwire to j-box and disconnect? Any opinions are appreciated, Akoni

My best advice is to hire an electrician who has lots of experience with PV systems to help you. PV systems have their own chapter in the NEC -- Chapter 690.

You've probably just dropped a good chunk of cash on PV system components, or maybe even a kit. To get the most out of this system and to make it safe, it has to be installed properly.

- Jim Katen, Oregon

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Thanks for the reply. I should have said equipment grounding conductor - it's for the metal frame of the solar modules. Didn't sound right to me either - the manufacturers rep gave me that information but I won't entertain that anymore. I think I'll run 1/2 inch EMT with compression fittings and weatherproof pulling ell's the whole way from outside -thru my attic - back to the outside. I haven't bought any equipment yet but I'm making my schematic for the permit - the electrician asked me to submit my plan and get it approved, then he'll help me. thanks, akoni

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Thanks for the reply. I should have said equipment grounding conductor - it's for the metal frame of the solar modules. Didn't sound right to me either - the manufacturers rep gave me that information but I won't entertain that anymore. I think I'll run 1/2 inch EMT with compression fittings and weatherproof pulling ell's the whole way from outside -thru my attic - back to the outside. I haven't bought any equipment yet but I'm making my schematic for the permit - the electrician asked me to submit my plan and get it approved, then he'll help me. thanks, akoni

What brand & model of PV panel are you getting?

Are you familiar with all of the incentives that Hawaii offers? Check it out here:

http://www.dsireusa.org

- Jim Katen, Oregon

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I can get solar world 175 watt modules for $817 retail here at the local supplier in Hawaii. From what I see, looks like a good deal and I can stay local. I'm just going to put maybe 4 modules up with 4 micro-inverters (net-meter). Thanks for the website, akoni

Thanks for the reply. I should have said equipment grounding conductor - it's for the metal frame of the solar modules. Didn't sound right to me either - the manufacturers rep gave me that information but I won't entertain that anymore. I think I'll run 1/2 inch EMT with compression fittings and weatherproof pulling ell's the whole way from outside -thru my attic - back to the outside. I haven't bought any equipment yet but I'm making my schematic for the permit - the electrician asked me to submit my plan and get it approved, then he'll help me. thanks, akoni

What brand & model of PV panel are you getting?

Are you familiar with all of the incentives that Hawaii offers? Check it out here:

http://www.dsireusa.org

- Jim Katen, Oregon

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