Control light and a time delayed bathroom fan with one double pole switch?

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zemingduan

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Philadelphia,PA
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Electrical Designer
Hi here is the situation. We have a bathroom fan that has time delayed feature. The 120V bathroom fan need a neutral wire and hot line directly landed at the fan's junction box. The fan also has two red wires that are control signal wire that need connect to a wall switch. According to the video, the two red control wires are not designed to carry current and shall not be attached to power. Please see the video (
) about the wiring of the fan. The third method in the video is the wiring method we need to use.

I want to control the light and fan with only one switch and when the switch is on, the light and fan will be on and when the switch is off the light is off but the fan is still on for a delayed period of time. I plan to use a double pole single throw (DPST). Please see the below wiring diagram I made.

Do you see any issue with it? Does the 20A 240V commercial DPST only be used for 240V appliance? Can it be used for this kind of application?

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zemingduan said:
I am not sure if the control wire is 120V or 24V. Does NEC allow the 24V control wire in the same box with the 120V power wire?
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Neither am I and they don't tell you. I don't think you can mix power and CL2 on the same switch either. A quick check with a meter of the control pair would give you the answer but I would give tech support a call to be sure. If it is indeed low voltage, I would install a separate switch in a box with a barrier or a separate box and switch for the light.

Is this a residential bath or commercial restroom?

-Hal
 
hbiss said:
Neither am I and they don't tell you. I don't think you can mix power and CL2 on the same switch either. A quick check with a meter of the control pair would give you the answer but I would give tech support a call to be sure. If it is indeed low voltage, I would install a separate switch in a box with a barrier or a separate box and switch for the light.

Is this a residential bath or commercial restroom?

-Hal
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This is residential bath.
 
Do you think this red control wire is Class 1 circuit as defined in NEC Article 725? 725.48 (B) (1) states the Class 1 control wire/signaling circuit can be installed in the same box with power-supply circuit only when equipment powered is functionally associated.

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In my case, the power circuit in the switch supply the a separate light which is not functionally associated with the fan control wire. Thus I guess this is a violation of 725.48(B) (1).
 
I've installed way too many of these fans and Panasonic provides no detailed info on the circuit class or any specific restrictions at all. I would just do as you suggested but if you're designing something for others to implement I'd contact Panasonic.
I use 14-2 for the fan control to a switch in the same box as the light switch without any concerns about anything. Panasonic issues no warnings at all.
 
hbiss said:
... I don't know anybody who wants the fan running every time they are in the bathroom. ...
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Parents of gassy kids, perhaps? Women with gassy husbands?

It will work, there's no doubt or disagreement about that.
As for complying with code ... the best information available to you doesn't say that the red wires are part of a Class 1 circuit, so you can't assume that Article 725 is applicable.
Instead of asking us whether it will strictly comply with the code, you might ask the AHJ whether it will be approved.
That, or specify some other fan whose manufacturer is more forthcoming and more cooperative.
 
hbiss said:
If it's residential just install two separate switches, one for the fan and one for the light. I don't know anybody who want's the fan running every time they are in the bathroom.

-Hal
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This fan with the muti speed plug module will be continuously running in low speed (30CFM) to meet the ventilation requirements. The switch is used to switch it to high speed/activate mode.
 
zemingduan said:
The switch is used to switch it to high speed/activate mode.
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And turn on the light, I understand that. But it's not clear whether you can do that with one switch, and I probably wouldn't want to anyway. Any residence I have done has a separate switch for the fan and another for the light(s). The light switch would be illuminated when off so that you can find it in the dark.

The fan is needed primarily when someone is taking a shower to remove moisture. Lysol works better for odors.

-Hal
 
hbiss said:
And turn on the light, I understand that. But it's not clear whether you can do that with one switch, and I probably wouldn't want to anyway. Any residence I have done has a separate switch for the fan and another for the light(s). The light switch would be illuminated when off so that you can find it in the dark.

The fan is needed primarily when someone is taking a shower to remove moisture. Lysol works better for odors.

-Hal
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And some fan/light systems include a humidistat to automatically run the fan at high speed when the humidity is high and keep it running after the light is turned off until the humidity is low enough.
 
GoldDigger said:
And some fan/light systems include a humidistat to automatically run the fan at high speed when the humidity is high and keep it running after the light is turned off until the humidity is low enough.
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That's right. This fan can also have humidistat module or occupancy sensor module you can plug in if you buy them.
 
zemingduan said:
This fan can also have humidistat module or occupancy sensor module you can plug in if you buy them.
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In which case you supply power to the fan constantly and not use the red leads. Certainly then the light gets it's own switch (unless that is on its own occupancy sensor also.) Something I would do for a commercial restroom.

-Hal
 
farmantenna said:
I've installed way too many of these fans and Panasonic provides no detailed info on the circuit class or any specific restrictions at all. I would just do as you suggested but if you're designing something for others to implement I'd contact Panasonic.
I use 14-2 for the fan control to a switch in the same box as the light switch without any concerns about anything. Panasonic issues no warnings at all.
Click to expand...
Same here and I've install close to 1000 of these fans. Maybe not that many but probably 500.
 
I will repeat my suggestion of putting a cube relay at the fan, coil wired to the light, that connects the red wires together when the light is on.
 
We run 14/2/2 to the fans. Use the black/white as power and red/white w/red stripe as control.

As I remember the red leads are part of the120 volt circuit but connected to the grounded (neutral) side of the fan.

I would love to have a discussion with the enginers at Panasonic as to what they were thinking when coming up with this design. All they had to do is use a black as constant power and red as a switch leg. Simple 14/3 to switch.
 
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