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Joined: Aug 2008
Posts: 10
S
Member
I cant find this in the NEC.
Is there a reference in the NEC to separate 24vdc and 120 vac into their own conduits?

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Joined: Mar 2003
Posts: 849
Y
Member
Try Article 725. 2005 NEC
725.26
725.41
725.55
Depending on the class of the 24volt.

Joined: Aug 2008
Posts: 10
S
Member
Thanks for the quick feedback.
Unfortunately I only have the 2008 NEC and 725.26 / 725.55 are no longer listed.

Joined: Mar 2003
Posts: 849
Y
Member
2008 NEC Article 725
725.48
725.136
Try thoses
Also read Article 725 Definitions for
Classes 1,2,3.

Joined: Aug 2008
Posts: 10
S
Member
Thanks.
It looks like the answer is yes it is acceptable for our situation.

Joined: May 2009
Posts: 20
B
Member
Sorting out when it's Ok and when it isn't seems an interesting subject.

Can you provide a few more project details that describe the application?

Thanks

Joined: Aug 2008
Posts: 10
S
Member
A rigid coduit connects a control panel with a metering device.
The device uses 120VAC for control power and has a contact that will have 24vdc going through it and used back at the control panel as an input to a PLC.

Joined: Jan 2001
Posts: 1,044
Tom Offline
Member
Since these circuits are functionally related, even if the 24 vdc is class 2 or class 3, you could take advantage of exception #2 to 725.130(A) and also apply 725.48(B)(1) and run the 24 vdc as a class 1 circuit.


Few things are harder to put up with than the annoyance of a good example.
Joined: May 2009
Posts: 20
B
Member
Shop_Test - As I understand it the two could in certain applications be serving the same device and be combined, but the NEC calls out certain separation devices and or distance that must be maintained between the conductors?

Tom- In the case of wiring as a Class 1 circuit (upgrade the wiring), NEC2005 725.27(A) would require 18 or 16 AWG and 725.27(B) would require 600 volt rated insulation of specific types?

Am I barking up the right tree?

Joined: Jun 2007
Posts: 301
J
Member
Same temperature rating, your good. Personally, I always separate power from control. Regardless of the situation. Just my way.

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