Fresh Air Kit - Motorized Damper Question

[jocool1585]

HVAC Masters - I'm adding a fresh air intake to my furnace in the garage and have purchased this kit:

http://www.amazon.com/gp/product/B002G747HC/?tag=atomicindus08-20

The motorized damper is 24v. I only want the damper to open when the furnace fan kicks on. Where should I pull power from and do I need to add a transformer to the mix and tap into the furnace fan wiring?

The furnace is a regular old 1980s natural gas house unit.

Thanks - Joe

 

[JBAUTO]

What furnace you got ? Take a pic of the board

 

[jocool1585]

Here's the board:

 

[jocool1585]

Here's the furnace info:

 

[brewchief]

jocool1585, that is a lennox pulse, if it hasn't been pressure tested in the last year or two by a lennox dealer I would highly recommend having it done, those furnaces have had a history of heat exchanger failures and I have had at least one family affected by CO poisoning due to it.

IIRC at least some versions of those had a accessory terminal designed for an electronic air cleaner or booster fan that would well for what you want to do.

 

[jocool1585]

brewchief - is there a way to pressure test it with standard pressure testing equipment? I haven't had any issues with it.

 

[danielzig]

Jocool - basically it consists of isolating the heat exchanger and pumping it up to 4 psi. If after 10 minutes, there is still pressure left, you are good. To isolate the exchanger you need to block the air inlet behind the flapper assembly, the gas inlet, and the exhaust pipe. You can use those rubber expandable plugs to do this.

I have a pulse that currently still heats my house, great furnace. They got such a bad wrap because of that initial heat exchanger problem though.

As far as your initial question goes, did you want the damper to open whenever the fan is on regardless of what mode the furnace is in?

 

[jocool1585]

Yes, just need 24v to the damper.

Thanks!

 

[danielzig]

Yes, just need 24v to the damper.

Thanks!

I don't know the power requirement of the damper. If it was low enough, you might just be able to tap into the white wire (w) at the terminal strip in the middle of the furnace. If the requirement exceeds the ability of the onboard transformer, you could get an aux transformer and wire it in series with a current sensing relay and the damper motor. Then, when the fan makes the current sensing relay, the damper motor will open.