High and low voltage in the same pipe.

[JeffKiper]

I have a question I can't find an answer to. Can I run 24vdc and 480 VAC in the same conduit? Old school thinking us no. I am lookig at motor local disconnects with aux switches for my vfd enable circuit. I understand making sure the insulation is rated at the highest voltage potential typically we use 480VAC so 600 v rated insulation applies.

Does anybody know where it is either allowed or disallowed?

 

[robo77]

I have seen it work, but the distance was limited (~50ft) and it worked.

I have also seen it not work and had to use quencharc's. (120vac inputs)

Try using shielded cable should work.

 

[leitmotif]

I have a question I can't find an answer to. Can I run 24vdc and 480 VAC in the same conduit? Old school thinking us no. I am lookig at motor local disconnects with aux switches for my vfd enable circuit. I understand making sure the insulation is rated at the highest voltage potential typically we use 480VAC so 600 v rated insulation applies.

Does anybody know where it is either allowed or disallowed?

Maybe allowed and maybe not - matters not to me. I do not think it is good practice to run signal and power conductors together and do not do it.

I am also leery about running multiple circuits thru one pipe even tho they are at same voltage.

Dan Bentler

 

[Bullzi]

I am with both posters. It is not a good idea to run AC and DC in the same conduit. I cant say that I have never done it but I try and avoid it. I made it work with 120VAC. It was a short run >10' and I had shielded cable. With 480 you may get too much induced voltage in the DC wires that the PLC shows a on state when the contact is open.

Is there any way you can get a separate conduit ran for that? If so I would have it done. The money it cost is nothing compared to the problems you could face.

If there no way to get a separate conduit then go with a good shielded cable and ground one end of the drain wire.

That is one of those times when you tell the customer " I will try and and if it works great. If it doesn't you will have to run more conduit."

 

[The Plc Kid]

Jeff

If you are using VFD cable with shield and foil per conductor then get the cable with the aux leads built in that are twisted and shieled and it works fine even on long runs.

I use Lapp VFD cable and they have this. Works well for using the aux on 120 VAC or 24 VDC.

 

[pino2003fr]

Jeff

If you are using VFD cable with shield and foil per conductor then get the cable with the aux leads built in that are twisted and shieled and it works fine even on long runs.

I use Lapp VFD cable and they have this. Works well for using the aux on 120 VAC or 24 VDC.

yes, i do agree, with you

 

[brstilson]

Can you do it? Sure. The real question though is "should you?" It's just plain bad practice. All I can think of is what happens when someone smashes a section of conduit and all of the sudden you have 480 volts applied to your DC circuit.

 

[pino2003fr]

Can you do it? Sure. The real question though is "should you?" It's just plain bad practice. All I can think of is what happens when someone smashes a section of conduit and all of the sudden you have 480 volts applied to your DC circuit.

the best way to do it , it by NFPA 70: National Electrical Code
you have to go by Hazardous classes, and divisions

 

[Bit_Bucket_07]

Can you do it? Sure. The real question though is "should you?" It's just plain bad practice. All I can think of is what happens when someone smashes a section of conduit and all of the sudden you have 480 volts applied to your DC circuit.

I could tell you first-hand what happens to 120VAC I/O in such a scenario.

It ain't pretty.

 

[FLAengineer]

Yes, from my experience here in South Florida I can just imagine when the local power company puts a surge on the incoming voltage, and it passes through to the 480 circuit. The induced voltage on the DC line could blow out devices on either end, or at least weaken them. You might get by for months or even longer with no problem, but a surge or short on the 480 will happen eventually..... not good practice running them together.

 

[locotumbler]

When i took NEC code classes based on the 1999 NEC it is not up to code to run different Voltages in the same raceway. Conduits are a no. If you have wire trough with a divider that meets the "different raceway" definition.