How do i interlock bathroom fan with furnace

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uche
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Joined: Thu Jan 25, 2018 10:53 pm

How do i interlock bathroom fan with furnace

Hello,

I am wondering what wire guage to use and how I can interlock the bathroom fan with the furnace so when fan for bathroom is switched on, the furnace starts. First I do not know the reason behind this since this bathroom fan exhaust to the outside (ducted to the outside). But I was told is the new code in Alberta, Canada. Any ideas on this. Thanks!

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Aaron
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Location: Minnesota, USA

Re: How do i interlock bathroom fan with furnace

Post by Aaron »

You do realize that is a very unusual configuration--to have your furnace fan always go on simultaneously with the bathroom fan?

It's not an easy task. You'd have to have some knowledge of electronics and relays. When you'd switch on your bathroom fan, you'd also be powering a 24 vac transformer that would need to send voltage down a wire to the furnace to call for the fan to be on. The electronics gets tricky because it would override your thermostat, but only when the stat doesn't call for the fan to be on. So you need some sort of logic circuit. That is above my pay grade.

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emtnut
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Re: How do i interlock bathroom fan with furnace

Post by emtnut »

uche wrote: ↑Tue Apr 24, 2018 1:20 pm Hello,

I am wondering what wire guage to use and how I can interlock the bathroom fan with the furnace so when fan for bathroom is switched on, the furnace starts. First I do not know the reason behind this since this bathroom fan exhaust to the outside (ducted to the outside). But I was told is the new code in Alberta, Canada. Any ideas on this. Thanks!

That is an Alberta building code requirement. I believe what they want is a 'centrally' located ventilation switch. When this switch is ON, and the fart fan turns on, then it automatically starts the furnace fan.
You need a 3 way switch for the exhaust fan, 2 way for the ventilation switch. From there you run 14/2 to a control transformer. A contact from the control transformer connects to the 'fan' control of your furnace (R and G).
All AC wiring would be 14/2 (14/3). On the low voltage side of the transformer (usually mounted near the furnace) you can use low voltage cable (16/2 or 18/2)

I would call your municipality on this. Building codes change and vary by region.

~~ Ford Ford Ford Ford Ford Ford :mrgreen: ~~

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Aaron
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Location: Minnesota, USA

Re: How do i interlock bathroom fan with furnace

Post by Aaron »

The fart fan! :lol: :D :lol:

Wow, I never heard of this code. Very interesting. Are bathroom odors--ahem, ODOURS--worse in the Alberta province? Might have to do with the tar sands? :lol:

At least the solution sounds relatively straightforward.

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Shannon
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Re: How do i interlock bathroom fan with furnace

Post by Shannon »

Ya I'm sure this would only be for a newer home with a "whole house 'ventilation. I would check with your local building code office before you go to the trouble.

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