Mixed wiring

[Brian D]

The company I work for has been runnig there control wiring(#18 THHN) with there 220v circuit(#6THHN). It is all for a condenser on the roof. Is this a code violation.

[ February 25, 2006, 08:12 AM: Message edited by: Brian D ]

 

[chevyx92]

Re: Mixed wiring

No. All the wires you mentioned are rated for 600V.

 

[infinity]

Re: Mixed wiring

It depends on the type of control circuits that they're using. Class 2 control wiring cannot be in the same raceway as power wiring regardless of the insulation voltage rating. I'd guess that the condenser unit is using class 2 controls which would make this a violation.

 

[infinity]

Re: Mixed wiring

Here is the reference:

725.55 Separation from Electric Light, Power, Class 1, Non?Power-Limited Fire Alarm Circuit Conductors, and Medium Power Network-Powered Broadband Communications Cables.
(A) General. Cables and conductors of Class 2 and Class 3 circuits shall not be placed in any cable, cable tray, compartment, enclosure, manhole, outlet box, device box, raceway, or similar fitting with conductors of electric light, power, Class 1, non?power-limited fire alarm circuits, and medium power network-powered broadband communications circuits unless permitted by 725.55(B) through 725.55(J).

 

[tom baker]

Re: Mixed wiring

chevyx92
Where is the rule that states this is allowed?

 

[chevyx92]

Re: Mixed wiring

725.26(B)(1)

 

[don_resqcapt19]

Re: Mixed wiring

Chevy,
That section only applies to Class 1 control circuits. Most HVAC equipment has Class 2 control circuits.
Don

 

[infinity]

Re: Mixed wiring

Originally posted by chevyx92:
No. All the wires you mentioned are rated for 600V.

This is a common misconception. The determining factor is the class of wiring used for the control circuits. As Don stated it is usually class 2. These conductors cannot be installed in the same raceway as power conductors.

 

[EEC]

Re: Mixed wiring

How do you classifly control circuits?

 

[infinity]

Re: Mixed wiring

Originally posted by EEC:
How do you classifly control circuits?

Classifications are outlined in Article 725.

 

[templdl]

Re: Mixed wiring

Check out NFPA79, Electrical Standards for Indudtrial Machinery. It recognizes wire form 30AWG to 1000, ref table 11.

 

[EEC]

Re: Mixed wiring

Where in NFPA 79 does it explain difference? Could you attach pdf of pages?

 

[don_resqcapt19]

Re: Mixed wiring

NFPA 79 does not apply to HVAC equipment. See the definition of industrial machinery in 3.3.55 in NFPA 79.
Don

 

[EEC]

Re: Mixed wiring

No where in NFPA 3.3.55 does it explain difference between classes of control circuits.

 

[chevyx92]

Re: Mixed wiring

Can someone give examples of class 1, 2 and 3 control circuits as article 725 doesnt paint a clear picture to me.

 

[RUWired]

Re: Mixed wiring

Chevyx92, A few examples of; class 1 circuits would be stop-start stations and door bells.These would be directly through a low voltage xfrmrs. Class 2 circuits would be t-stat wiring, speaker,nurses call, newer fire alarm systems,garage door operator circuits.These would be via a circuit board.
Rick

 

[don_resqcapt19]

Re: Mixed wiring

For Class 2 and 3, the power supply must be listed and identified as such.
Don