Wednesday, April 02, 2008

What is the difference between CL2 and CL3?

CL2 is the designation for Class 2 Circuit wire and CL3 is the designation for Class 3 Circuit wire. Both are regulated under NEC Article 725. They are both used for remote-control, signaling, and power-limited circuits. In plain English that means that CL2 and CL3 are types of multi-purpose wire used for things like security systems, speaker wire, intercom systems, nurse call buttons, and more.

The difference between the two is that CL2 is rated for up to 150 volts while CL3 is rated for up to 300 volts. (NEC 725.71 F) According to NEC 725.2, CL2 offers some protection from electric shock while CL3 offers a bit more because it is rated to carry more voltage.

CL3 may be used in place of CL2, but not the other way around.


At May 9, 2008 at 6:42 PM, Anonymous Anonymous said...

What is typically different in the wire itself between a CL2 and CL3 rated wire? Are the number of strands the same for both types or is it possible that a CL3 rated wire will always have more strands of copper than a CL2 wire?

At October 28, 2008 at 2:37 PM, Anonymous Anonymous said...

I believe Cl2 circuitry and cables refer to 30 volt or less not 150 volt

At October 29, 2008 at 10:44 AM, Blogger Will Hunt said...

I believe that you are wrong and that my original posting was/is correct. CL2 is rated up to 150 volts and CL3 up to 300. Here is a link to an article on UL's website that confirms my thoughts -

At March 21, 2009 at 8:51 PM, Anonymous Anonymous said...

CL2 30 volt, 100 volt amp(power)
CL3 >30 volt, >0.5 but not greater than 100 volt amp I don't think the other guy is right if you are not sure don't confuse other people that is trying to get a right answer

At January 30, 2012 at 12:44 PM, Anonymous Anonymous said...

150v or 300v is the insulation rating not the operational voltage. nec < 30v <100va

At January 8, 2013 at 1:48 PM, Anonymous Anonymous said...

CL2 is code for residential and CL3 is for commercial what I was taught was it was the way the cable burns in case of a fire it's rating of the jacket on the cable.

At January 8, 2013 at 2:06 PM, Blogger Will Hunt said...

I'm sorry, but whoever taught you that was wrong. As I've said and as I linked to, CL2 means it is rated to 150 Volts and CL3 is rated to 300 Volts.

The way the cable burns is called the flame rating and in cable this is designated by CMX, CM, CMR, CMP, etc.

For instance, CMR is known as Riser Rated cable and can be installed in the walls of homes and offices. And like the sound of it's name it can also be run from floor to floor unlike regular CM cable that can be run in walls, but shouldn't be run vertically from floor to floor.

At February 21, 2013 at 11:12 AM, Anonymous Anonymous said...

Hey Will... thanks for the link to UL.
CL3 FT4. Suitable for 12vdc 5a?

At July 26, 2013 at 8:25 PM, Blogger joshlove26 said...

Can speaker wire be used for powering low voltage devices like security cameras?

At October 12, 2013 at 2:52 PM, Anonymous Anonymous said...

Yes. I use 18/2 to power cameras.

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At May 26, 2016 at 10:56 AM, Anonymous Leo Cole said...

I was going to buy the 12 gauge cl2 rated wire from monoprice, but I have been reading about cl3 rate wire. Is it necessary?

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