# Class 1,2 and 3 wiring



## Julius793 (Nov 29, 2011)

Can anyone explain to me what makes a low voltage circuit class 1,2 or 3? Is it the wire, transformer, nature of the circuit, Ect... In addition where would I find it in the nec. Any help is greatly appreciated 

Ps. This is NOT for a side job :thumbsup:


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## Dennis Alwon (May 9, 2009)

Julius793 said:


> Can anyone explain to me what makes a circuit class 1,2 or 3? Is it the wire, transformer, nature of the circuit, Ect... In addition where would I find it in the nec. Any help is greatly appreciated
> 
> Ps. This is NOT for a side job :thumbsup:


I have never gotten a good answer for class 2 or class 3. There must be some guidelines that determine whether a trany is class 2 or class 3. Look at chapter 5 art. 501, 502 and 503


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## Julius793 (Nov 29, 2011)

Dennis Alwon said:


> I have never gotten a good answer for class 2 or class 3. There must be some guidelines that determine whether a trany is class 2 or class 3. Look at chapter 5 art. 501, 502 and 503


Sorry for the confusion i edited my post. I was talking about low voltage circuits.


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## Dennis Alwon (May 9, 2009)

Julius793 said:


> Sorry for the confusion i edited my post. I was talking about low voltage circuits.


I was also for the most part. The transformer determines the class.


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## raider1 (Jan 22, 2007)

Take a look at Chapter 9 Table 11(A) for AC circuits and 11(B) for DC circuits for the different power source limitations for Class 2 & 3 circuits.

Class 1 circuits can be up to 600 volts and not power limited.

Also check out the definitions in Article 725.

Chris


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## Julius793 (Nov 29, 2011)

Dennis Alwon said:


> I was also for the most part. The transformer determines the class.


Now I'm confused isn't article 501,502 and 503 about hazardous location?


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## Dennis Alwon (May 9, 2009)

Julius793 said:


> Now I'm confused isn't article 501,502 and 503 about hazardous location?



Yes I was thinking low voltage but put the wrong articles. Chris got you there.


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## Julius793 (Nov 29, 2011)

Dennis Alwon said:


> I was also for the most part. The transformer determines the class.


Ok just to clarify till I get a chance to read article 725. If I would like to put line voltage and low voltage in the same conduit all I would do is check the class of the transformer? Then if it's class 1 I could do it and if it's class 2 or 3 I wouldn't be permitted?


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## Pete m. (Nov 19, 2011)

Julius793 said:


> Then if it's class 1 I could do it and if it's class 2 or 3 I wouldn't be permitted?


See 725.48 for Class 1

725.136 for Class 2 and 3

Pete


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## jbfan (Jan 22, 2007)

http://ecmweb.com/mag/electric_understanding_nec_circuit/

I found this to help explain it to me.
It is based on the 2002 code, but answered my question.


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## CoopElec (May 16, 2011)

*Class 3 cable*

I remember I had a question on the test about the temperature rating of the insulation of a class 3 cable?


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## Big John (May 23, 2010)

I always thought Class 2 rating depended solely on the power supply. If it had a "class 2" listing then that applied to the circuit. 

Because I know under certain circumstances you can mix high and low voltage, one of the stipulations being that you remove the "class 2" labeling from the low-voltage power source.

-John


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