ECN Forum

When is a Class 2 circuit, isn't?....

Posted By: sparkyinak

When is a Class 2 circuit, isn't?.... - 12/16/16 03:34 AM

For Ghits and Siggles....

If a Class 2 circuit is protected by an properly sized OCPD, is it really a Class 2 circuit or is it a Class 1 circuit and can be treated as a Class 1 circuit as long it meets the requirements of a Class 1 circuit as needed?

....and go!
Posted By: gfretwell

Re: When is a Class 2 circuit, isn't?.... - 12/17/16 07:44 AM

A class 2 is inherently protected by the limited current power supply so the only reason for OCP is protecting equipment.
Posted By: sparkyinak

Re: When is a Class 2 circuit, isn't?.... - 12/17/16 10:52 PM

I understand what a class 2 circuit is, hence the question. I'm not abvocating this but let's say one need to dim LED lights (0-10V) and there's no practical way to run a seperate raceway to the light. If one would properly fused the dimmer circuit and used appropriate voltage rated wire, could both the lighting circuit and dimmer circuit be in the same raceway?
Posted By: HotLine1

Re: When is a Class 2 circuit, isn't?.... - 12/17/16 11:40 PM

Based on your scenario...I see no problem.

Posted By: Potseal

Re: When is a Class 2 circuit, isn't?.... - 12/18/16 06:01 AM

I might be misunderstanding the scenario but if the light is 120V AC and the dimming is 0-10V DC and they are both in the same raceway running parallel over a long distance isn't there a possible issue of interference with the AC to the DC? Sparkyinak's scenario might be to code but ultimately it could lead to problems.
Posted By: sparkyinak

Re: When is a Class 2 circuit, isn't?.... - 12/18/16 06:12 AM

Granted this is all hypothetical but with your theory has possible merit. In a situation like that, I'd use shielded cable for the signaling.
Posted By: gfretwell

Re: When is a Class 2 circuit, isn't?.... - 12/18/16 09:06 AM

I have questioned the Class 1 thing a few times and it is possible. You just need to follow all of the class 1 rules from end to end.

The chance of coupling harmful amounts of 60hz in any raceway that is not measured in miles is infinitesimal.
You are generally talking about 2 balanced conductors for each voltage. The twist necessary at 60hz is what you see on transmission lines.

If the raceway is actually a "duct" (referenced but undefined in the NEC) cable jackets can be the isolation although they usually have an additional isolating innerduct/raceway in there.

BTW along these lines, I have also heard the argument that a cable jacket is "isolation" so if you had a chapter 3 and a 725 cable in the same raceway, they are isolated. You just can't terminate them in the same box (generally).
The scenario was you have a raceway with a (say Romex) in it. You have "T" body conduit body at each end just before you enter the chapter 3 box. You come in the side with a low voltage cable and exit before you get to the box on the other end. Is that legal?

It is a conversation starter anyway.
Posted By: sparkyinak

Re: When is a Class 2 circuit, isn't?.... - 12/19/16 08:14 AM

I'd have to grab my code book from the office. Interesting question. My initial take is if the signal circuit is class 2 or 3 circuit, I'd say no
Posted By: HotLine1

Re: When is a Class 2 circuit, isn't?.... - 12/19/16 03:58 PM

Guys:

This months issue of EC Magazine has an ad for "Encore Wire" new MC-LED AL cable. Seems to solve any issues like this.

I have not read it thoroughly, but on a quick read seems OK

www.encorewire.com is the website in the ad.

Posted By: gfretwell

Re: When is a Class 2 circuit, isn't?.... - 12/19/16 11:34 PM

Combo class 2/3 plus chapter 3 cables have been around for quite a while.
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