Code: 12VDC and 120VAC

[mouchot]

When dealing with portable buildings or trailer offices, can 12VDC be run through the same conduit as 120VAC, or does it have to have seperate conduit? What are the code requirments?

Thanks.

 

[charlie b]

Yes, but only if the insulation system of the 12VDC wires is rated for 120 volts or higher. 300.3(C)(1).

 

[iwire]

Those sound a lot like manufactured buildings and would have meet certain standards before they left the factory.


What is the nature of the wiring?

 

[infinity]

He should be concerned about the Class of the 12 VDC conductors also. Class 2 and 3 conductors can not go in the same raceway with 120 volt conductors regardless of their insulation value.

 

[dereckbc]

From a technical point of view, you would not want to consider this as it is likely AC voltages would be induced onto the 12 VDC circuits.

From a code point of view it can be done if certain conditions are met. The most important is the cable insulation rating. The low voltage circuits must be equal or greater than the 120 VAC circuit. For example if both are THHW, then that is OK becuase they both are 600 V rated.

You must also identify by some means to differentiate between the two circuits like insulation color. I wouldn't do it unless you are talking about something like the 12 VDC just being used for things like head lights, turn signals, etc.

However if this is for an automotive purpose like an RV, boat, or trailer, none of the NEC rules apply anyway.

 

[steved]

However if this is for an automotive purpose like an RV, boat, or trailer, none of the NEC rules apply anyway.

If it were an RV the ANSI/RVIA 12V Standard would require the 12VDC and 120VAC wiring to be separated by a 1/2" gap or other approved means, such as split corrugated loom over one set of wires.

 

[don_resqcapt19]

Dereck,

From a code point of view it can be done if certain conditions are met. The most important is the cable insulation rating. The low voltage circuits must be equal or greater than the 120 VAC circuit. For example if both are THHW, then that is OK becuase they both are 600 V rated.

While the insulation rating is important the type of low voltage circuit is also important and in many case the rules in the Chapter 7 articles prohibit the mixing of the conductors.

However if this is for an automotive purpose like an RV, boat, or trailer, none of the NEC rules apply anyway.

Actually Article 551 covers RVs, but starting with the 2005 edition, that article does not cover the low voltage systems in the RV. In the 2002 code, 551.10(C)(3) said: "Separation. Battery and dc circuits shall be physically separated by at least a 13-mm (?-in.) gap or other approved means from circuits of a different power source."
Don
Don