T-stat Wire for LV Dimming

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jap

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I went to a house under construction just to look around and the electrician had 2 conductor t-stat wire taped to the 12/2 romex that was run from each switch location to the undercabinet lights.

Best I could tell it was for the 0-10v dimming for the fixtures they were going to be installed.

I feel the wire for the LV dimming needed to be the same voltage rating as the romex.

Is there something I'm not seeing here or is there something that would allow this ?

JAP>
 
jap said:
I went to a house under construction just to look around and the electrician had 2 conductor t-stat wire taped to the 12/2 romex that was run from each switch location to the undercabinet lights.

Best I could tell it was for the 0-10v dimming for the fixtures they were going to be installed.

I feel the wire for the LV dimming needed to be the same voltage rating as the romex.

Is there something I'm not seeing here or is there something that would allow this ?

JAP>
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I'm not sure what the t-stat wire would be for but, it would need to be rated at 600v in order to be in the fixture with romex or in the switch box for that matter. I believe Lutron makes a 0-10v wall switch now. Are you sure it's just "t-stat" wire? Lots of wire manufactures make LV wire rated for 600v.
 
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grizwald said:
I'm not sure what the t-stat wire would be for but, it would need to be rated at 600v in order to be in the fixture with romex or in the switch box for that matter.
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I disagree... T-stat wire need only be rated 120V assuming that is the voltage of the fixture

(C) Conductors of Different Systems.
(1) 1000 Volts, Nominal, or Less. Conductors of ac and dc
circuits, rated 1000 volts, nominal, or less, shall be permitted
to occupy the same equipment wiring enclosure, cable,
or raceway. All conductors shall have an insulation rating
equal to at least the maximum circuit voltage applied to any
conductor within the enclosure, cable, or raceway
Click to expand...

IMO, T-stat wire would be a bad choice and to be honest I m noat sure if it is compliant or not. I have used class 2 wiring that was 12/2.

I have also used 14/4 nm Many of the fixtures I have seen have 4 wires installed within a rubber cord so I see no reason why the 0-10v dimming needs to be in a separate cable. Some fixtures may require it.
 
Dennis Alwon said:
I disagree... T-stat wire need only be rated 120V assuming that is the voltage of the fixture



IMO, T-stat wire would be a bad choice and to be honest I m noat sure if it is compliant or not. I have used class 2 wiring that was 12/2.

I have also used 14/4 nm Many of the fixtures I have seen have 4 wires installed within a rubber cord so I see no reason why the 0-10v dimming needs to be in a separate cable. Some fixtures may require it.
Click to expand...

Interesting Dennis...maybe it's a San Francisco thing? Let me look into it a bit. I've had inspectors try to call me on mixing LV wire and romex in the same box. Everywhere is a bit different on their interpretations and enforcement.
 
grizwald said:
Interesting Dennis...maybe it's a San Francisco thing? Let me look into it a bit. I've had inspectors try to call me on mixing LV wire and romex in the same box. Everywhere is a bit different on their interpretations and enforcement.
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300.3(C)(1) is an easy read. Art. 725 gives me a headache beyond my worst New Year's Day hangover, maybe someone in San Francisco can make sense of it.
 
grizwald said:
Interesting Dennis...maybe it's a San Francisco thing? Let me look into it a bit. I've had inspectors try to call me on mixing LV wire and romex in the same box. Everywhere is a bit different on their interpretations and enforcement.
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It can be in the same box depending on what class the low voltage wiring may be. Action Dave gave the link
 
Isn't T-stat wire typically installed in the same enclosure as the power conductors when used for heating and AC controls?
 
infinity said:
Isn't T-stat wire typically installed in the same enclosure as the power conductors when used for heating and AC controls?
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Generally their is a separate compartment and older units had the contacts on the outside. I have seen the low voltage wires from the units stick outside the unit and connection made there. The outdoor units have a separate knockout and compartment. That has been my experience but I haven't install one in some time
 
wwhitney said:
I thought the LV dimming wires are a class 2 circuit and can't be part of the same "cable" as power conductors. In the MC world, that's why Type MC-PCS cable was developed, but I haven't heard of anything similar in NM cable.

Cheers, Wayne
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Some dimmers allow either Class 1 or Class 2 operation, allowing the circuit to be treated as Class 1 using Chapter 3 wiring methods (not T-stat wire) which can then be combined with power wiring if the control and power are related.
 
Dennis Alwon said:
It can be in the same box depending on what class the low voltage wiring may be. Action Dave gave the link
Click to expand...
I have little to no experience with these dimming methods, but I agree - one needs to look carefully at the dimming system and determine if it is class 1 or 2, or in some cases sounds like you have a choice, but in those instances once you decide to make one component/portion of the circuit class 2 - the entire control circuit must be treated as class 2, you can not pick and choose methods for different sections of the control circuit.

infinity said:
Isn't T-stat wire typically installed in the same enclosure as the power conductors when used for heating and AC controls?
Click to expand...
Yes, as well as lots of other things that use class 2 controls overhead door operators is another common application that comes to mind. We typically enter the same space but do not enter via the same opening as the power circuit, inside there usually is dividers or other physical separation of low and high voltage wiring, the factory components of listed equipment however may bundle all those conductors together in places - but our field wiring and interface between field and factory wiring generally needs to be separated.

wwhitney said:
I thought the LV dimming wires are a class 2 circuit and can't be part of the same "cable" as power conductors. In the MC world, that's why Type MC-PCS cable was developed, but I haven't heard of anything similar in NM cable.

Cheers, Wayne
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Just because it is LV doesn't automatically mean it is class 2. Like said before some maybe are some maybe not, some maybe you can choose, but once you go class 2 all of same control circuit needs to be class 2.
 
The Ballasts are 120v then have a Purple and Grey out of the ballast that are used for 0-10v dimming.
Very common commercially, and the wiring used commercially is usually 600v rated.

But the T-Stat wire that was in the house roughin was not rated for 300v and that's where my question arose.

JAP>
 
wwhitney said:
I thought the LV dimming wires are a class 2 circuit and can't be part of the same "cable" as power conductors. In the MC world, that's why Type MC-PCS cable was developed, but I haven't heard of anything similar in NM cable.

Cheers, Wayne
Click to expand...

Well the fixtures we just hung had a rubber cord with 5 wires in it-- nothing special about the wiring- Black, White, Green and Red & Yellow for the dimming
 
Class 2 circuits can be open splices & NM can be used for class 2 wiring -- If what you have is not class 2 there is a violation somewhere -- class 2 & line voltage can be in the same box attached to a common device uitlizing both voltages. need 1/4" separation though
 
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