125VDC cable mixed in with 120VAC

[mshields]

I have to run both 125VDC and 120VAC power from a switchgear lineup with 125VDC control and which has 120VAC, CPTS's for non control related requirements, to some pad mounted switchgear. I have a couple of conduits running via handholes out to these pad mounted units, I'm wondering if there is any problem running the two voltages through the same handholes. It seems to me that so long as the cable is standard 600V THHN/THWN, there not an issue. IIt's the AC vs DC thing that concerns me. Should it?

 

[Gregg Harris]

I have to run both 125VDC and 120VAC power from a switchgear lineup with 125VDC control and which has 120VAC, CPTS's for non control related requirements, to some pad mounted switchgear. I have a couple of conduits running via handholes out to these pad mounted units, I'm wondering if there is any problem running the two voltages through the same handholes. It seems to me that so long as the cable is standard 600V THHN/THWN, there not an issue. IIt's the AC vs DC thing that concerns me. Should it?

Good to go
300.3 Conductors.
(C) Conductors of Different Systems.
(1) 600 Volts, Nominal, or Less. Conductors of ac and dc circuits, rated 600 volts, nominal, or less, shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway

 

[GoldDigger]

But if the 125 DC is a separate supply system rather than just a control voltage, you need to have a plan for distinguishing the conductors.


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[SG-1]

The only consideration I have is if a non-control conductor suffers insulation failure, you could loose the control power. This would mean all protective relays, breaker close & trip circuits would become inoperative.

 

[don_resqcapt19]

Just like for the low voltage conductors, you have to look to the rules in 725. The 125VDC conductors are likely Class 1 control circuits and there are some rules for separating those conductors from other conductors. 725.48