Grounding for 320Amps or 40Amps?

[Dale Hayes]

(3) 1 1/2"NPT conduit runs

(3) 1 1/2"NPT conduit runs

There are provisions for (3) 1 1/2"NPT conduit runs between the controls enclosure and the steel flange that contains the (8) 40KW circuits. (24) 6GA conductors will be installed through the conduit.

 

[augie47]

the plot thickens.
my vote: either
{A} (1) #10 thru each of the three conduits based on 250.122 &
300.3(B)
or

{B} none,if your conduits qualify under 250.118

 

[cpal]

I agree with Augie and I would certainly use metallic nipples or raceways from the J box to the flange, and forget the seperate EGC's ( if I'm understanding you correctly??).

 

[Dale Hayes]

The 500Amp Circuit Breaker?

The 500Amp Circuit Breaker?

I am still pondering this grounding situation.

There are (3) 1 1/2"NPT conduits connecting the (8) 40Amp Resistive loads to the controls enclosure.

There is the 500Amp Circuit breaker in the controls enclosure.

If a fault occurs at the load side of the 500Amp circuit breaker wouldn't that fault make its way through the controls enclosure steel walls, through the conduits, to the steel flange that contains the (8) 40Amp Resistive loads?

 

[cpal]

I am still pondering this grounding situation.

There are (3) 1 1/2"NPT conduits connecting the (8) 40Amp Resistive loads to the controls enclosure.

There is the 500Amp Circuit breaker in the controls enclosure.

If a fault occurs at the load side of the 500Amp circuit breaker wouldn't that fault make its way through the controls enclosure steel walls, through the conduits, to the steel flange that contains the (8) 40Amp Resistive loads?

yes, it should!

 

[Dale Hayes]

Grounding for 320Amps or 40Amps?

Since there are two fault possibilities - one at 320Amps and the other at 40Amps, and both fault conditions have access across the steel enclosure, the conduit and the steel flange - should grounding from the steel flange that has the (8) 40Amp circuits be for 320Amps or 40Amps?