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PV DC Disconnects and Separate Building Grounding

Posted By Eric Jensen, Wednesday, May 22, 2013

I've always followed two Code requirements: That a building has an electrical disconnecting means at the building served and that  electrical systems in a building use a common grounding electrode.

However, if I have a multibuilding apartment complex that has the PV array on a separate building from the inverter and I have the DC output circuit(s) leaving the array building I can find no Code justification for PV complaince with:

  • PV disconnect at the array building or
  • A connection from the DC array equipment grounding system to the (array building) electrode system.

So, if I want to turn off power at the array building, I may turn off the non-PV system (utility power) at the building disconnecting means however the DC circuits remain energized and I begin looking for the inverter location.

If I'm on the roof and simultaneously contact both an air conditioner (referenced to the (array building) electrode system) and an module or rack frame (referenced to the (inverter building) grounding electrode system) I will have a difference in ground potential between the two electrode systems with resulting current flow through my body.

Both items (lack of local disconnect and building grounding) seem counter to established Code requirements.  However I can not find in the Code where they are required.

Sticking points: 690.14(C): "disconnect all conductors": No need: PV conductors are independent of (array building) utility conductors. Building disconnect:  225.31:  Not a branch circuit or feeder (photovoltaic output circuit), Article does not apply.

Let me know what you think.

Eric

 

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