Class 2 Wiring....

mstrlucky74

Senior Member
I know we've discussed this before but it a bit fuzzy and I want to be clear.

1. Class 2 wiring can't be run with power(600v) conductors. The only way to do this is re-classified them as class 1 and that entails removing all class 2 marking from power supplies etc.?
2. Class 2 wiring can be run exposed(not enclosed in conduit) above hung ceilings?
3. Class 2 wiring is rated for 150v?


Interesting that this MC-PCS cable is allowed for class 1 and class 2 wiring method. I mentioned this a while ago but can't locate the post.

https://www.southwire.com/products/35959.htm
 

mstrlucky74

Senior Member
When you have an MC job is great you can you the MC-PCS but what about when you have an all EMT job?? I was thinking the whips from the integral 0-10drivers could be the MC-PCS cable but then I'd be landing that cable in a common j-box and splicing the 120v and 0-10v in same box. Is that allowed even if I ran the class 2 0-10v free air and not in conduit from there?

The triangle is the 0-10v wire and the circle is the 120v.
 

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ActionDave

Moderator
Staff member
I don't know how legal I was but on LED retro fits with all conduit I pulled 16 AWG TFFN in the EMT and flex that served the lights.
 

kwired

Electron manager
I don't know how legal I was but on LED retro fits with all conduit I pulled 16 AWG TFFN in the EMT and flex that served the lights.
Branch circuit taps for luminaires is legal, but need more details to know if what you did was legal. If entire branch circuit was run with 16 AWG, it probably wasn't legal, taps from the main circuit to individual luminaires with 16 AWG very possibly was legal.
 

kwired

Electron manager
When you have an MC job is great you can you the MC-PCS but what about when you have an all EMT job?? I was thinking the whips from the integral 0-10drivers could be the MC-PCS cable but then I'd be landing that cable in a common j-box and splicing the 120v and 0-10v in same box. Is that allowed even if I ran the class 2 0-10v free air and not in conduit from there?

The triangle is the 0-10v wire and the circle is the 120v.
Just because it is 0-10 volt doesn't automatically mean this control loop is a class 2 circuit.
 

ActionDave

Moderator
Staff member
Branch circuit taps for luminaires is legal, but need more details to know if what you did was legal. If entire branch circuit was run with 16 AWG, it probably wasn't legal, taps from the main circuit to individual luminaires with 16 AWG very possibly was legal.
The TFFN was for the 0-10V dimming.
 

petersonra

Senior Member
So is it ok per code to run class 2 without conduit?

Sent from my SM-N960U using Tapatalk
725.3 Other Articles. Circuits and equipment shall comply
with the articles or sections listed in 725.3(A) through (N).
Only those sections of Article 300 referenced in this article
shall apply to Class 1, Class 2, and Class 3 circuits.
Does it say anywhere in article 725 that class 2 circuits require conduit?
 

kwired

Electron manager
I looked at the fixture driver cuts and they are marked class 2.
Which means you can use class 2 wiring methods and other class 2 items on the circuit.

You also are allowed to reclassify it as class 1 and run the wires in same conduit as your power wiring, but that also means the entire control circuit gets reclassified as class 1. You can not mix and match things to suit your wants/needs once you do this.
 

mstrlucky74

Senior Member
I see nowhere in Section 725 that class 2 and 120v can’t be in the same box. Issue is I have 120v(in conduit) and class 2 dimming going to the same ballast/driver in a fixture. I’m bring the class 2 “free air” and the 120v

Scenario #1 – Have power conduit going directly into downlight box. Guess one could just bring in the 0-10v class 2 into a different ko on the box as it’s attached to the downlight.

Scenario #2- Tricky one. Would one need separate whips to separate j-boxes for the 0-10v class 2.?

Thanks.
 

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kwired

Electron manager
I see nowhere in Section 725 that class 2 and 120v can’t be in the same box. Issue is I have 120v(in conduit) and class 2 dimming going to the same ballast/driver in a fixture. I’m bring the class 2 “free air” and the 120v

Scenario #1 – Have power conduit going directly into downlight box. Guess one could just bring in the 0-10v class 2 into a different ko on the box as it’s attached to the downlight.

Scenario #2- Tricky one. Would one need separate whips to separate j-boxes for the 0-10v class 2.?

Thanks.
If 0-10V is indeed class 2 they must be in separate wiring methods or a listed assembly that effectively separates the two circuits per the listing.

If it is class 2 circuit that has been "reclassified" then it is no longer a class 2 circuit. But that means the entire circuit becomes class 1, you can't throw in class 2 cabling or devices wherever you decide is convenient.

More common example over the years of this is HVAC thermostat wiring. If you decided to reclassify the control circuit as class 1 circuit to be able to run thermostat wiring with the supply power wiring - you can't run typical 18 ga thermostat cable in the raceway, it would have to be 300 or 600 volt conductors. You also can not connect it to typical 24 volt class 2 rated wall thermostat - it would have to be a thermostat rated for line voltage since it is not a class 2 circuit even though it is still 24 volts.
 

mstrlucky74

Senior Member
So spoke to engineer yesterday and he said you can combine class 2 with 120v power wiring if the class 2 insulation id rated for 600v. I've heard of this before but thought there was a caveat. Maybe it's the reclassifying if you do this???
 

kwired

Electron manager
So spoke to engineer yesterday and he said you can combine class 2 with 120v power wiring if the class 2 insulation id rated for 600v. I've heard of this before but thought there was a caveat. Maybe it's the reclassifying if you do this???
You must use insulation rated for highest voltage present in the cable/raceway. Normally you are using 600 volt rated conductors, with 120 volt power circuit being present you only would be required to have 120 volt insulation - though something rated either 300 or 600 volts will be much more common to come up with.

You also still must "reclassify" the entire class 2 circuit. That means you can't just run 600 volt conductor where you wish to run with power conductors, you must also land in devices rated for class 1/power applications.

See 725.130 exception 2 and informational note that follows.
 

mstrlucky74

Senior Member
You must use insulation rated for highest voltage present in the cable/raceway. Normally you are using 600 volt rated conductors, with 120 volt power circuit being present you only would be required to have 120 volt insulation - though something rated either 300 or 600 volts will be much more common to come up with.

You also still must "reclassify" the entire class 2 circuit. That means you can't just run 600 volt conductor where you wish to run with power conductors, you must also land in devices rated for class 1/power applications.

See 725.130 exception 2 and informational note that follows.
Thanks, I thought so.
 
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