Furnace blowing Hot & Cold!?


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Old 11-28-07, 07:28 PM
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Furnace blowing Hot & Cold!?

Ok this is a strange one. I just bought a 1950's house with a pretty new furnace. Now, in the finished basement, each room has two vents...one blowing hot air, and one blowing cold! So no matter what we set the temp to, the rooms do not heat up.
Can anyone clue me in as to why this may be happening, and more importantly, how to overcome it?

Much appreciated
crazybrit.
 
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Old 11-28-07, 08:24 PM
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Does it blow when the system is not running?

Do you have an air exchanger? (ERV)

Is this vent at the same area (wall/ceiling), or no?
 
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Old 11-29-07, 12:43 PM
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Hi Jay no it doesn't blow when off, just when I start up the temp and the furnace kicks on.
The vents are in the same locations ie same room on the wall only on opposite walls and one blows hot while the other blows cold.
As far as an ERV not quite sure what that is.
Thanks.
 
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Old 11-29-07, 03:05 PM
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Are you able to follow this pipe back to it's source? or what is on the back side of this cold pipe?

ERV (Energy Recovery Ventilation) is another word "Air Exchanger".
 
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Old 11-29-07, 03:19 PM
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My guess is that if only two registers, at same height, and not one being low on the wall, that both were intended for heat and they are using the pathway out the door to a common return. My guess is that the cold blowing register is not hooked up, because someone determined later that 2 heat registers in the room were unnecessary, and what they didn't realize is that suction, as the air leaves the room, is pulling basement air through that register.

You can be more certain it is basement temp air if you use a thermometer and first take temp of basement and then take temp of cold air blowing out that register to rule out possibility of some outside makeup air coming in. If the basement temp and the cold air register temp are the same, then I believe more in my first paragraph theory.

Does the cold register 'blow' as hard as the one with heat, or is it less, yet still blows?

I'd see if you can trace the ducting. But if you can't, I am betting you can just close down that register. That is if both registers have damper controls on them. (Do they?)
 
 

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