Grounding/Bonding EGC in EMT

[photovoltaics]

I have a DC conduit run in EMT going from a photovoltaic array to the inverter. The conduit run contains a positive, negative, and an insulated (not bare) EGC (not a GEC).

The conduit run starts with a ground bushing on the roof and ends with a ground bushing at the inverter. But there is a pull box in between. The conduits that enter and exit the pull box just have plastic pull bushings but I put a ground bar in the pull box through which the EGC lands (unbroken) before it continues on.

My question is does this suffice? Or do I absolutely need ground bushings or myers hubs entering and exiting the pull box?

Thanks in advance.

 

[jaggedben]

You haven't specified how the raceways are connected to the pullbox, but you probably need grounding bushings.

In 2008 it's a bit vague but in 2011 it has been made explicit (in 250.64 (E)) that you have to use the methods specified in in 250.92. (B)(2) through (4).

(2) Connections utilizing threaded couplings or threaded hubs on enclosures if made up wrenchtight.
(3) Threadless couplings and connectors if made up tight for metal raceways and metal-clad cables.
(4) Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers.

(Red is 2011 changes.)

It is basically the same question as in this thread:
http://forums.mikeholt.com/showthre...-conductor-raceway-shared-with-branch-circuit

 

[photovoltaics]

"You haven't specified how the raceways are connected to the pullbox, but you probably need grounding bushings."

Both the conduit entering and the conduit exiting the pull box are connected to the box with threaded lock rings on the inside of the box. Ground bushings are only at the start and end of the run. The pull box has a ground bar which connects to the egc wire.

So the run is as follows:

dc disconnect-ground bushing-emt-lock ring-pull box-lock ring-emt-ground bushing-inverter

 

[jaggedben]

I'm assuming the PV voltage is more than 250V. In that case, 250.97 applies.

If the pull box connections are through oversize, eccentric, or concentric knockouts, you need a bonding bushing or equivalent. If not, you need 'fittings with shoulders that seat firmly against the box', which includes EMT connectors so you may be okay.

In the (solar) company I work for we pretty much just use bonding bushings on every non-threaded connection, since in 99 out of 100 cases it seems to be required.