low voltage wiring in same box as 120 v

Stevenfyeager

Senior Member
Heated floors: Doesn't the thermostat wire in the wall thermostat box go against not being able to have low voltage and 120 volts in the same box? Thank you
 

hbiss

EC, Westchester, New York NEC: 2014
We've answered that exact same question before someplace. As I remember the thermostat has LV tails that are of TFFN that you run outside the box to splice in the wall with the LV wire from the temperature sensor.

-Hal
 

JFletcher

Senior Member
w/o looking, I believe it's under 725.136. Associated limited energy (thermostat here) wiring can be in the same box if physically separated by a barrier or by 1/4" physical separation.
 

Stevenfyeager

Senior Member
w/o looking, I believe it's under 725.136. Associated limited energy (thermostat here) wiring can be in the same box if physically separated by a barrier or by 1/4" physical separation.
The thermostats I've been wiring (the tile man usually purchases in my cases recently) require the line wires and thermostat wire both fasten to the thermostat, so how would we separate them? Thanks
 

JFletcher

Senior Member
The thermostats I've been wiring (the tile man usually purchases in my cases recently) require the line wires and thermostat wire both fasten to the thermostat, so how would we separate them? Thanks
or by 1/4" physical separation, routing them 1/4" apart; 725.136(D). The thermostats I've used have the terminals spaced fairly well apart and on different planes and/or angles.

Another way to do it is notch the drywall and/or box a tad and bring the thermostat wire around the box and thru the notch tho it's not necessary imo.
 

Stevenfyeager

Senior Member
or by 1/4" physical separation, routing them 1/4" apart; 725.136(D). The thermostats I've used have the terminals spaced fairly well apart and on different planes and/or angles.

Another way to do it is notch the drywall and/or box a tad and bring the thermostat wire around the box and thru the notch tho it's not necessary imo.
Thank you
 

infinity

Moderator
Staff member
The thermostats I've been wiring (the tile man usually purchases in my cases recently) require the line wires and thermostat wire both fasten to the thermostat, so how would we separate them? Thanks

After you push it back into the box it's anyone's guess as the whether or not the 1/4" separation still exists.
 
Last edited:

GoldDigger

Moderator
Staff member
Aren't they both LV?
OK. In one characterization they are both low rather than medium voltage.
But 12 or 24 V is considered low (less than 50V) in another characterization.
It is also likely to be Class 2 or Class 3 limited power.

Sent from my XT1585 using Tapatalk
 

JFletcher

Senior Member
After you push it back into the box it's anyone's guess as the whether or not the 1/4" partition still exists.
No more than pushing a bare EGC back in the box wont contact the neutral or ungrounded terminals. If there is .1", it's enough, same as 12/24V and 120V, even if it'd not up to code.
 

kwired

Electron manager
Is it not listed as it is, making what NEC says somewhat irrelevant as long as you follow instructions that are part of the listing?
 
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