Quazite Boxes and Conduit Bonding

[SelectCo]

On site we have a long run of 2 1/2" RMC containing three 3/0 thhn conductors with #4 AWG thhn Grd.
Due to the distance Quazite Boxes have been installed as Pull points.
Voltage is 480V 3ph.

I have instructed the contractor to install Bonding bushings on each conduit and connect (#4 AWG) or use Fiber Bushings and provide a acceptable and approved bonding jumper between conduits.
I reference NEC 250.96 NEC 250.97 NEC 344.46 and NEC 300.4G.
Is there any other articles that apply and/or do any of these not apply.

As for the #4 EGC.
It is my understanding that this can pass thru the pull points uninterrupted.
Is this correct?


FYI: Terminating to a distribution block and 60Amp Breaker (with compression reducers).


thanks.

 

[augie47]

On site we have a long run of 2 1/2" RMC containing three 3/0 thhn conductors with #4 AWG thhn Grd.
Due to the distance Quazite Boxes have been installed as Pull points.
Voltage is 480V 3ph.

I have instructed the contractor to install Bonding bushings on each conduit and connect (#4 AWG) or use Fiber Bushings and provide a acceptable and approved bonding jumper between conduits.
I reference NEC 250.96 NEC 250.97 NEC 344.46 and NEC 300.4G.
Is there any other articles that apply and/or do any of these not apply.

As for the #4 EGC.
It is my understanding that this can pass thru the pull points uninterrupted.
Is this correct?


FYI: Terminating to a distribution block and 60Amp Breaker (with compression reducers).


thanks.

I see no problem with the "plan", however I do question the #4 as your EGC.
You mention "terminating" on a 60 amp breaker. If the supply breaker is a 60 amp the "normal" wire would be a #6 phase conductor with a #10 EGC. If you are increasing the phase conductors to 3/0 to compensate for voltage drop, 250.122(B) requires a proportional increase in the EGC which, if my math is correct, would require a #1

{side note: I don't have my 11 Code handy, but according to '08 Art your 300.4(G) might be (H) }

 

[kwired]

I don't want to put this thread in the wrong direction here but this is a perfect example of how the requirement in 250.122(B) is not necessarily something that makes sense in all situations. This topic comes up from time to time, but I don't necessarily recall as good of examples as what we can get from the situation presented by the OP in this thread. Augie if you want to move this to a new thread, that is fine with me, but I think we need links between the threads.

The OP has a 200 amp conductor, and a 4 AWG EGC.

If the conductor is supplied by a 200 amp overcurrent device 250.122 says the EGC needs to be at least 6 AWG.

If the conductor is supplied by a 60 amp overcurrent device 250.122 says (according to Augie's calculation, I did not double check it) the EGC needs to be at least 1 AWG.

So 250.122(B) is saying in this case that a 6 AWG is sufficient to carry the necessary current to open a fault supplied through a 200 amp overcurrent device, but change that overcurrent device to 60 amps and leave everything else the same and you need a 1 AWG to carry the necessary current to open a smaller overcurrent device.

 

[SelectCo]

Thanks gentlemen for the input and I apologize for indicating the incorrect size on the EGC.
The installed conductor is #2.

The question stems from knowing how an installation should appear and then getting questionedas to where it is indicated in the NEC.
I had little problem with the bushing question it is the continuous path for the bond on which I could use any additional insight.

Thanks again,
micheal.

 

[augie47]

250.96 & 250.97 should suffice for a reason.
(and I still believe your now #2 is too small by Code)

 

[RUWired]

(and I still believe your now #2 is too small by Code)

# 2 awg is good. With a normal 6 awg phase conductor (26240 cir mills) and a new size 3/0 phase conductor (167800) the multiplier is 6.39. # 10 awg ground ( 10380 ) x 6.39 is 66328 cir mills. # 2 awg is 66360 cir mills. Just makes it.

 

[augie47]

I carried my multiplier out a couple of more decimal points ( 6.3948) which took me over #2 a hair.... but I would concede #2