AC- DC SAME CONDUIT

[dm9289]

I have an application where it would be very convienent to run 250VDC and single phase 240VAC in same conduit. It does not feel right but I could not find code prohibiting this. Does anyone know if this a code compliant install.

Thanks
Dave

 

[iwire]

I have an application where it would be very convienent to run 250VDC and single phase 240VAC in same conduit. It does not feel right but I could not find code prohibiting this. Does anyone know if this a code compliant install.

No one knows based on the info we have.

There is no general NEC prohibition against running AC and DC in the same raceway but there are rules about running power conductors with other classes of conductors.

For instance you cannot run a class 2 AC door bell circuit in the same conduit as a 120 AC lighting circuit unless you jump through some hoops.

You will need to tell us about each of the circuits and what they run before we can really help you.

 

[ADub]

No one knows based on the info we have.

There is no general NEC prohibition against running AC and DC in the same raceway but there are rules about running power conductors with other classes of conductors.

For instance you cannot run a class 2 AC door bell circuit in the same conduit as a 120 AC lighting circuit unless you jump through some hoops.

You will need to tell us about each of the circuits and what they run before we can really help you.

The jumping through hoops for that scenario would simply be using a class 1 method and taking the "class 2" label off the transformer no?

 

[dm9289]

Thank you for your reply
The 240VAC 6A is for a battery charger output current
The 250VDC with a 30A breaker is the power leaving the batteries 20 cells for power to a switch gear charging motor used roughly 4 times per year.
During normal operation the 250VDC is supplied by a rectifier, during our annual outage we will use the 250VDC battery source when the rectifier is down via a transfer switch.
During normal plant operation this circuit on either end of the transfer switch does not function only used to rack in and out breakers for maint window.

Thanks
Dave

 

[Smart $]

Thank you for your reply
The 240VAC 6A is for a battery charger output current
The 250VDC with a 30A breaker is the power leaving the batteries 20 cells for power to a switch gear charging motor used roughly 4 times per year.
During normal operation the 250VDC is supplied by a rectifier, during our annual outage we will use the 250VDC battery source when the rectifier is down via a transfer switch.
During normal plant operation this circuit on either end of the transfer switch does not function only used to rack in and out breakers for maint window.

Thanks
Dave

You can run your AC and DC circuits in the same conduit. They are both considered power circuits.

 

[dm9289]

Thank you very much

 

[kwired]

The jumping through hoops for that scenario would simply be using a class 1 method and taking the "class 2" label off the transformer no?

That option involves more then just removing the label though. You must use all class 1 wiring methods as well - so your door bell transformer would need to be inside an enclosure not just the high voltage side (as is typical), the chime would need to be class 1 rated or installed in a cabinet (probably not as effective of a device when this is done), have it's class 2 label removed, and would need supplied via class 1 wiring methods, not your typical bell or thermostat wire, and same would go for the typical class 1 rated push buttons, although the push button is the one thing that is easier to come up with acceptable solutions for.

 

[kwired]

No one knows based on the info we have.

There is no general NEC prohibition against running AC and DC in the same raceway but there are rules about running power conductors with other classes of conductors.

For instance you cannot run a class 2 AC door bell circuit in the same conduit as a 120 AC lighting circuit unless you jump through some hoops.

You will need to tell us about each of the circuits and what they run before we can really help you.

OP asked if AC and DC can be in same conduit. Your example is AC and AC.
But yes class 2 in same conduit with class 1 or power circuits is a problem and probably what you were after.

Some tend to think all DC circuits are class 2 - though there is a lot of limited power DC stuff out there it is not always true.

 

[MasterTheNEC]

I have an application where it would be very convienent to run 250VDC and single phase 240VAC in same conduit. It does not feel right but I could not find code prohibiting this. Does anyone know if this a code compliant install.

Thanks
Dave

See NEC 300.3(C)(1)

 

[big john]

That option involves more then just removing the label though. You must use all class 1 wiring methods as well....

In addition to that, the Class 1 circuit still needs to be functionally associated with the power conductors it runs with. 725.48(B)(1)

 

[iwire]

The jumping through hoops for that scenario would simply be using a class 1 method and taking the "class 2" label off the transformer no?

Yes, lets say you do that. Now your door bell button at the front door needs an electrical enclosure, and the terminals on that transformer are going to have to be enclosed as well.

I would call it a pain.

 

[iwire]

See NEC 300.3(C)(1)

That is such a part answer it really strikes me as misleading when people only cite that one section.

To me first you need to figure out if running the circuits together is allowed in the first place and than if they are you must also comply with 300.3(C)

 

[MasterTheNEC]

That is such a part answer it really strikes me as misleading when people only cite that one section.

To me first you need to figure out if running the circuits together is allowed in the first place and than if they are you must also comply with 300.3(C)

He did "it would be very convenient to run 250VDC and single phase 240VAC in same conduit." then he felt it was wrong...the reference directly answer the minimalist approach answer to the actual question:angel:

EDIT - Why...because office says I provide (4) pages of history and code information for a Yes or No type question. So I am trying to reduce my responses...lol

 

[don_resqcapt19]

He did "it would be very convenient to run 250VDC and single phase 240VAC in same conduit." then he felt it was wrong...the reference directly answer the minimalist approach answer to the actual question:angel: ...

Without more information, we don't know if that is the correct answer. One circuit could be an unrelated Article 725 Class 1 control circuit....

 

[MasterTheNEC]

Without more information, we don't know if that is the correct answer. One circuit could be an unrelated Article 725 Class 1 control circuit....

Thats why you simply answer with the information given (which is why it is so important to ask what want.....in a question)

If the answer was simply can I install DC and AC Conductors in the same raceway then....my answer applies...if other variables apply....ask them in the question is my rational for answering open ended questions.

 

[don_resqcapt19]

Thats why you simply answer with the information given (which is why it is so important to ask what want.....in a question)

If the answer was simply can I install DC and AC Conductors in the same raceway then....my answer applies...if other variables apply....ask them in the question is my rational for answering open ended questions.

I will never directly answer a question like this one as it does a dis-service to the forum readers. I will answer maybe and ask some questions.