0-10 volt dimming question

[GerryB]

If you have an existing lighting circuit, 277v or 120v, if you fish the dimming cable into the switch box does it become a class 1 circuit needing 600v insulation or would 300v insulation be compliant? I know the mc cable with the dimmer cable has 600 v insul. but that is in the same jacket. Thanks

 

[MasterTheNEC]

Review Section 725.136(A)-(I) for your answers.

 

[GerryB]

Review Section 725.136(A)-(I) for your answers.

I did look at that section, a little confusing. I came up with:
725.136(A)-..class 2 & 3 shall not be placed in any ...outlet box...with class 1...
725.136(B)-separated by barrier. Obviously can't be done in a single gang box.
725.136(D)(1) and(2)-both talk about a .25" clearance. This I am not sure of if they are in the same box and go to the same device.
725.136(D)(2)(B) sends you to 725.41 and makes it a class 1 circuit, so 600 volt insulation, is what I come up with.
(looking at the 2011 right now, but we are on the 2014)

 

[hbiss]

If you have an existing lighting circuit, 277v or 120v, if you fish the dimming cable into the switch box does it become a class 1 circuit needing 600v insulation or would 300v insulation be compliant? I know the mc cable with the dimmer cable has 600 v insul. but that is in the same jacket. Thanks

A variation of this same question comes up every month. The answer is to reclassify the 0-10 as a Class 1 circuit. In your case, fish two conductor MC, AC or Romex for the dimming.

By the way, the voltage rating of low voltage and communications cables is not supposed to be printed on the jacket or spool because we are not supposed to use that number in deciding how to use the cable. Those cables are only supposed to be used according to Art 725 and 800 on.

-Hal

 

[GerryB]

A variation of this same question comes up every month. The answer is to reclassify the 0-10 as a Class 1 circuit. In your case, fish two conductor MC, AC or Romex for the dimming.

By the way, the voltage rating of low voltage and communications cables is not supposed to be printed on the jacket or spool because we are not supposed to use that number in deciding how to use the cable. Those cables are only supposed to be used according to Art 725 and 800 on.

-Hal

That's what I said, it becomes or you make it a class 1 circuit. I'm told you can get 18 gauge, purple and grey in 600 volt insulation, luminaire cable, but maybe not. It's a drop ceiling, 277 volt, commercial. I wouldn't use romex.

 

[hbiss]

Luminary cable is MC that has the two THHN power conductors plus a separate 18/2 cable under the same sheath. Because the 18/2 is a separate cable, not conductors, it fulfills the separation requirement between it and the power conductors in the MC. So in the MC the 18/2 low voltage remains CL2.

The 600V listing on the 18/2 comes into play when the MC and the LV cable gets stripped down to the individual conductors in the dimmer box and fixture. The 18/2 being 600V eliminates the separation requirement between LV and line voltage in the box. So in that respect I guess the CL2 does get reclassified. It's all very confusing I know.

Now, consider that you can just reclassify the CL2 and use 4 conductor MC or AC or run conduit and pull 4 conductors of THHN and do the same thing. However some AHJs may have a problem with the interpretation of when you can reclassify so I assume that's why luminary cable came into being.

I didn't mention above that you could run a CL2 cable between the dimmer and fixture BUT then you would have to deal with separation or dividers in the box and fixture. My feeling is that in your case just fish another run of MC and nobody can complain.

-Hal

 

[GerryB]

Luminary cable is MC that has the two THHN power conductors plus a separate 18/2 cable under the same sheath. Because the 18/2 is a separate cable, not conductors, it fulfills the separation requirement between it and the power conductors in the MC. So in the MC the 18/2 low voltage remains CL2.

The 600V listing on the 18/2 comes into play when the MC and the LV cable gets stripped down to the individual conductors in the dimmer box and fixture. The 18/2 being 600V eliminates the separation requirement between LV and line voltage in the box. So in that respect I guess the CL2 does get reclassified. It's all very confusing I know.

Now, consider that you can just reclassify the CL2 and use 4 conductor MC or AC or run conduit and pull 4 conductors of THHN and do the same thing. However some AHJs may have a problem with the interpretation of when you can reclassify so I assume that's why luminary cable came into being.

I didn't mention above that you could run a CL2 cable between the dimmer and fixture BUT then you would have to deal with separation or dividers in the box and fixture. My feeling is that in your case just fish another run of MC and nobody can complain.

-Hal

Ok, good explanation. Also if multi gang switches you could have 480 in the box.

 

[kwired]

That's what I said, it becomes or you make it a class 1 circuit. I'm told you can get 18 gauge, purple and grey in 600 volt insulation, luminaire cable, but maybe not. It's a drop ceiling, 277 volt, commercial. I wouldn't use romex.

Yes types TFFN/TFN/TEWN/MTW