Bare EGC All the Way to the Main Service Panel?

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tokeefe

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Camarillo, CA, USA
I recently participated in an install in Oregon where I was told the bare copper EGC would tie into a j-box along with our expensive PV wire to convert to THWN-2 which would exclusively run all the way back to the main service panel. I have a coworker however who is adament that the bare copper be continuously run from the roof all the way to the PV sub-panel beside the main. This means we have the cable ground(s) and bare ground run together (though seperated by conduit).

I guess my question then is whether or not I am allowed to transition my bare copper EGC to a cable grounding conductor (on the roof if possible) before reaching my sub or main panel? I wonder if this is the result of a recent code change? I cannot find the requirement in 2011's 690 (except of course for a "continuous" run, whatever that means).

By the way, I don't know if this makes any difference but the install run was DC as we used an SMA string inverter but my coworker's case in point is AC as it is leaving a microinverter branch.
 
tokeefe said:
I recently participated in an install in Oregon where I was told the bare copper EGC would tie into a j-box along with our expensive PV wire to convert to THWN-2 which would exclusively run all the way back to the main service panel. I have a coworker however who is adament that the bare copper be continuously run from the roof all the way to the PV sub-panel beside the main. This means we have the cable ground(s) and bare ground run together (though seperated by conduit).

I guess my question then is whether or not I am allowed to transition my bare copper EGC to a cable grounding conductor (on the roof if possible) before reaching my sub or main panel? I wonder if this is the result of a recent code change? I cannot find the requirement in 2011's 690 (except of course for a "continuous" run, whatever that means).

By the way, I don't know if this makes any difference but the install run was DC as we used an SMA string inverter but my coworker's case in point is AC as it is leaving a microinverter branch.
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You can transition from bare copper to insulated stranded conductor at the combiner/transition box.
 
I think your co-worker is making two mistakes:

1) Thinking that the GEC for a solar system must be 'unspliced' while forgetting that having it 'irreversibly spliced' is an option. See 690.47 (C)(3), in 2011 NEC. (The requirements are worded completely differently in the 2008 NEC, but are actually the same.)

2) Thinking that all the requirements for the GEC on a micro-inverter system also apply to the DC EGC on a string system. Personally I think it's a good idea to irreversibly splice the DC EGC, but I don't think it is required by the code.

It is generally NOT a good idea to pull bare copper with other conductors in a raceway. Besides being a PITA, it increases the odds of damaged insulation and faults. We only do it for short conduit jumpers between arrays, where we are avoiding the use of junction boxes, and where it is run with USE-2.
 
I agree with ggun. Common practice I've seen is to transition from bare Cu to THWN-2 in combiner box and bring the DC EGC down to the DC disconnect. Irreversibly crimp the DC GEC to the DC EGC in the DC disconnect and rout to grounding electrode by one of the methods in 690.47. Note also that in 2011 690.47 (C) (3) allows a common DC GEC and AC EGC as jaggedben mentioned, properly sized of course. Maybe this is what your co worker is thinking of? That or they are thinking of the additional array groundingthat was required in 2008 690.47 (D) and confused? In any case I would read up on 690 V
 
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