Lighting, Light Fixtures, Ceiling and Exhaust Fans - Replacing low voltage fan switches.....

Hi,

I've done a fair amount of traditional (110/220) wiring so when I visited my sister several months ago, I volunteered to replace several of her bathroom fan switches. I've ordered & received the switches (made by Venmar) - the instructions are woefully inadequate (they just describe how to cut a hole in the wall for the switches, nothing on wiring). I took apart one of her switches when I visited her - they are low voltage and have 3 wires coming in. When I visit her in a couple of weeks the wiring should be simple since I'm replacing the same switch.

I've never dealt with low voltage wiring and have a few questions:

There are 5 switches to replace - they run a central exhaust fan. I'd guess that the wiring for all comes from a single circuit, would this be correct? And since this is all low voltage, would there be a transformer somewhere that steps the voltage down? Would most electricians put such a transformer near the main box and would it look like a transformer you'd see for common appliances?

Finally, do I need to power that circuit/transformer down when I do this work? I guess that is the first question, if I don't then I don't need to find the transformer.

Thanks!

Bob

Not familiar with Venmar I did some looking around. Looks to me like it is the same or similar to an air exchanger. Are you installing the switches new (as in there was never a switch there before) or just replacing existing switches?
If you are just replacing existing then just wire them the same as the old ones.

For new you will need to run some low voltage cable either from the unit to each switch or daisy chain the switches with the final run back to the unit. The unit should have a location to connect the wires. and you shouldn't need any transformer as the unit should provide the power it needs for control.

The amount of wires you need will depend on how many functions the switches control. If it is just an on/off switch you will need two wires. One for the line one for "on" but if it is something like high/med/low/off you would need four wires. one for the line and then one for each speed.

If you have a model number and/or a wiring diagram that would be helpful for us to tell you what you need.

Tolyn,

Thanks for the reply. I am replacing the original switches with an exact match, the original switches have seen better times. So wiring is the easy part. The switch is model 12030 - a 20 minute lighted push button remote for an air exchanger (I think they are made in Canada).

So wiring is simple, my question is - since it is low voltage, can I just wire them without turning off power to that circuit or could that cause problems?

Thanks again!
Bob

If it is a new, replacing an exact match then all you should need to do is disconnect the Venmar unit by pulling the cord. While the low voltage will not hurt you, you could (though I doubt it) damage the control board of the unit by accidentally crossing the wrong wires.

To be clear, the low voltage power is likely coming from a transformer that is inside the Venmar unit. Similar to a furnace. That is why you need to disconnect the unit.