Cold Air Return - Booster Fan for Exterior Air - Direction?


Old 02-23-14, 08:08 PM
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Cold Air Return - Booster Fan for Exterior Air - Direction?

Hello all,

I have a 2007-built home with an HE natural gas furnace, as is de rigueur here in Calgary, Alberta, Canada.

Recently my brother pointed out that he thinks my booster fan is blowing the wrong direction - and I think I agree with him, but was looking for some semi-pro's to give me their two cents.

Here is the setup photos further along):

I have a booster fan that is powered by a typical wall switch beside my thermostat. I have confirmed that the booster fan does not come on during normal furnace operation, but only when I flip this switch. The switch turns on the furnace's blower motor to circulate air and engages this blower motor.

I believe the purpose is for summer days (we don't have AC up here, generally) to bring in cooler fresh air into the house.

However, based on the quasi-arrow on this unit ( I assume the white arrow surrounding the "2100" points in the flow direction for the fan?), it looks like the blower fan is sucking air FROM the cold air return OUTSIDE?!

Does this setup make sense to you guys? It's a relatively new home that passed code, obviously, so you'd think it's right, but it seems backwards as a summer re-circulation fan setup to my layman eyes...

Appreciate any comments.

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Old 02-23-14, 08:12 PM
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I should also note, I have the normal exterior-air supply "combustion air" intae that drops from the outside to right beside my furnance to bring in fresh air for combustion... So this is sepreate, and I belive 100% relaced to the reciruclation fan...

Does it make sense that it's blowing out of the house through the CAR (Cold Air Return), or should it be blowing outside air into the CAR?

Old 02-24-14, 05:21 AM
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Seems it intent is to exhaust which would make sense in the summer, especially in the evenings. Is there a check valve on there so your not pulling ice cold air into the heating system during the winter?
Old 02-24-14, 05:51 AM
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I would need to know more about your house and this setup, but energy efficient homes will often have fresh air requirements other than just venting cooler air in in the summer. The air tight nature of an energy efficient home limits the natural ventilation required for indoor air quality. To meet this need home designs will include a H/ERV system (hear or energy recovery ventilation) or simple an exhaust ventilator.

Did the house come with any energy audit papers?

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