Combined DC GEC & AC EGC under 2008 NEC?

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SunFish

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Can anyone clarify if the 2008 NEC allows for a combined DC GEC & AC EGC as described in 690.47(C)(3) of the 2011 & 2014 codes? 690.47(C) is pretty darn confusing in the 2008 code.

I am designing a job for an AHJ that is still operating under the 2008 NEC and using a transformerless inverter that doesn't have a terminal for a DC GEC. What would be the best way to go about installing a DC GEC to make the inspector happy?
 
SunFish said:
Can anyone clarify if the 2008 NEC allows for a combined DC GEC & AC EGC as described in 690.47(C)(3) of the 2011 & 2014 codes? 690.47(C) is pretty darn confusing in the 2008 code.

I am designing a job for an AHJ that is still operating under the 2008 NEC and using a transformerless inverter that doesn't have a terminal for a DC GEC. What would be the best way to go about installing a DC GEC to make the inspector happy?
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If it is a transformerless inverter than you will not need a GEC. Think of a transformerless inverter just like a normal electrical load: hot, maybe neutral, equipment grounding conductor. Interestingly, I dont think the 2008 specifically requires a string fused in each DC conductor.
 
SunFish said:
Can anyone clarify if the 2008 NEC allows for a combined DC GEC & AC EGC as described in 690.47(C)(3) of the 2011 & 2014 codes? 690.47(C) is pretty darn confusing in the 2008 code.

I am designing a job for an AHJ that is still operating under the 2008 NEC and using a transformerless inverter that doesn't have a terminal for a DC GEC. What would be the best way to go about installing a DC GEC to make the inspector happy?
Click to expand...

Show the inspector this SolarPro article, and ask for an exception:
http://solarprofessional.com/articl...rounded-pv-power-systems-in-the-nec/page/0/11

A GEC is not required for a non-isolated inverter, and if the inverter adheres to the UL 1741 requirements, it will not even have a GEC terminal. According to Wiles, ?The UL standard requires a grounding electrode conductor terminal ? only when there is a bonding jumper in the direct current (dc) side of the inverter.?
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Most transformerless inverters that do have a GEC terminal, really just have a redundant EGC terminal that is labeled as a GEC. You can connect a GEC if you want, but it isn't really necessary. Connect an ordinary AC EGC and you are done.

As far as I understand the "combined EGC/GEC", the requirements would be as follows:
1. Sized for the larger of 250.122 (AC EGC sizing) and 250.166 (GEC sizing).
2. Irreversibly spliced all the way from the inverter to the grounding electrode.
3. Bonded to both sides of all iron-based conduit through which it is routed.
4. Connected to the EGC terminals of all intermediate equipment.
 
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