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LeGrand (Pass & Seymour) make a multi-control single pole switch with a split tab TM8113WCC, which allows for the control of two independent circuits on a single yoke (one box). Code question: is it permissible to run a mains voltage (120V) circuit on one side of this device and a low-voltage circuit on the other?

  • My use case: I bought a new Panasonic WhisperGreen Select fan. The fan runs on mains power (120V), but the control of the fan is done by a signal loop to the fans circuity. In other words, power goes directly into the fan, but control of the fan is a low-voltage loop to the wall switch and back - separate power and control. If it works for this use, the LeGrand switch would look "cleaner" in my bathroom, and I'd avoid cutting in another box. All other multi-control switches are all common-cource, which won't work with this fan. – the_meter413 Feb 26 '15 at 21:37
  • What is the voltage of the control circuit? – Tester101 Feb 27 '15 at 1:10
  • What's the model number of the fan you're installing? I can't seem to find a WhisperGreen that uses a low voltage control circuit. – Tester101 Feb 27 '15 at 1:48
  • @Tester101 The WhisperGreen Select fans (all models, I think) have plug-and-play modules as options. My specific fan is FV-05-11VKL1 with the constant-on module and the humidity sensor options. With the constant-on module, the fan no longer uses mains power for ON/OFF, but the control loop for AUTO/RUN. – the_meter413 Feb 27 '15 at 19:29
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This is OK provided that the wires to the fan control switch are treated as 120VAC wires as per 725.46:

Class 1 Circuit Wiring Methods. Class I circuits shall be installed in accordance with Part I of Article 300 and with the wiring methods from the appropriate articles in Chapter 3.

(i.e. run using NM and not communications-type cable/wire) and as per 725.48(B)(1):

(B) Class 1 Circuits with Power-Supply Circuits. Class 1 circuits shall be permitted to be installed with power-supply conductors as specified in 725.48(B)(1) through (B)(4).

(1) In a Cable, Enclosure, or Raceway. Class 1 circuits and power-supply circuits shall be permitted to occupy the same cable, enclosure, or raceway only where the equipment powered is functionally associated.

since the control wires are with the fan's power wires, and we can safely treat them as a Class 1 control circuit using the provisions of 725.130, Exception 2:

Exception No.2: Class 2 and Class 3 circuits shall be permitted to be reclassified and installed as Class 1 circuits if the Class 2 and Class 3 markings required in 725.124 are eliminated and the entire circuit is installed using the wiring methods and materials in accordance with Part II, Class 1 circuits.

  • The downside to wiring it with regular NM cable is that when the nexy guy comes along to replace that switch, they will probably assume its 120V, and wire it up in a way that blows up the fan's electronics. – Grant Mar 1 '15 at 23:15
  • @Grant -- 725.46 says you must use a Chapter 3 wiring method when installing a Class 1 control circuit. I personally would wire it as a 14-4 with black/white for 120VAC and red/blue going to the switch, and have tags on both ends of the red and blue wires marking them as Class 1 control wiring. Anybody who cross-wires a properly labeled Class 1 control circuit to 120VAC and blows something up as a result can replace it out of their own pocket ;) – ThreePhaseEel Mar 2 '15 at 0:38

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