Class 1, Class 2, and Class 3 Circuit Identification

[jbuthmann]

Article 725.30 seems to require some sort of labeling to distinguish Class 1, Class 2, and Class 3 circuits from other circuits. The stated reason is to prevent "unintentional interference" with other circuits during testing and servicing.

Can someone with more experience in this area interpret the meaning of this article?
What does "unintentional interference" mean?
What kind of identification methods are acceptable?
Do individual conductors need to be labeled?
If all conductors have unique wire number labels and the numbers are identified on a schematic drawing, is that acceptable?
If groups of terminals are physically separated in panel but otherwise unmarked, is that acceptable.

 

[petersonra]

Article 725.30 seems to require some sort of labeling to distinguish Class 1, Class 2, and Class 3 circuits from other circuits. The stated reason is to prevent "unintentional interference" with other circuits during testing and servicing.

Can someone with more experience in this area interpret the meaning of this article?
What does "unintentional interference" mean?

Class 1, Class 2, and Class 3 circuits shall be identified
at terminal and junction locations in a manner that
prevents unintentional interference with other circuits during
testing and servicing

One of those poorly defined phrases one finds often in the code. I don't think there is a very good answer to it, certainly none that all will agree with.

What kind of identification methods are acceptable?

Anything that clearly identifies it as a class 1/2/3 circuit. I don't think it has to be identified as a specific circuit such as "Alarm circuit #6". If it is in a box that is identified as being for the alarm circuits, that is adequate IMO. Get a sharpie and write "ALARM" on the jbox.

Do individual conductors need to be labeled?

I don't think even individual cables have to be labeled. In fact, if there is some logical inference that can be drawn about a particular circuit from the physical location, type of cabling, or other physical factor, I think that is adequate.

If all conductors have unique wire number labels and the numbers are identified on a schematic drawing, is that acceptable?

I think that is acceptable but goes beyond the minimum requirements.

If groups of terminals are physically separated in panel but otherwise unmarked, is that acceptable.

Quite possibly IMO. For instance, if you identitied all such circuits in the building in this way. Think about a pushdown block. is there any need to label it?

 

[hbiss]

I agree. Also keep in mind that these circuits are not normally allowed to be co-mingled with others so identification is a moot point.

-Hal