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Old 06-18-2011, 06:14 PM   #1
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Old A/c unit tied into new furnace...any problems?


Instead of paying 4 grand for a a/c unit which I can't afford, I tied my $400.00 in the door a/c unit into my cold air return. I have the a/c unit in a basement window and I am running fan only on my trane xr95 high eff furnace.


It is bowing cold air around the house and works good.

Any way that I am gonna screw up my furnace or furnace fan?

Just checking if I may be making a bad decision?


Thanks!

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Old 06-18-2011, 06:18 PM   #2
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Old A/c unit tied into new furnace...any problems?


Will cause condensation inside the heat exchanger and rust it out from he inside out.

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Old 06-18-2011, 10:13 PM   #3
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Old A/c unit tied into new furnace...any problems?


I agree

After running it for one day I got a ton of condensation from the piping...it won't work...ah nice wasted day!
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Old 06-18-2011, 11:29 PM   #4
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Old A/c unit tied into new furnace...any problems?


But at least you found out before it harmed your furnace permanently.
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Old 06-19-2011, 08:56 AM   #5
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Old A/c unit tied into new furnace...any problems?


That is definetly a positive.

I wired from G on the furnace to G on the thermostat. Now I can turn the fan on or off - to act like a summer fan. I cut in 2 cold air returns in the basement, one on either end of the return.

Would that cause any problems I'm unaware of?


Also I am not sure about the thermostat, I have heard that this may be a multistage fan and that I should get a thermostat that can run the fan at different speeds?

And thirdly, is there any way to have the "summer fan" I wired in - have it kick in at a certain tempurature or certain time of day...then I wouldn't have to wake up and manually turn the summer fan on.

Thanks!
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Old 06-19-2011, 12:13 PM   #6
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Old A/c unit tied into new furnace...any problems?


Quote:
Originally Posted by hellothere123 View Post
That is definetly a positive.

I wired from G on the furnace to G on the thermostat. Now I can turn the fan on or off - to act like a summer fan. I cut in 2 cold air returns in the basement, one on either end of the return.

Would that cause any problems I'm unaware of?

Depends how cold the air is coming into the furnace.


Also I am not sure about the thermostat, I have heard that this may be a multistage fan and that I should get a thermostat that can run the fan at different speeds?

Multispeed fans aren't controlled by the thermostat as far as what speed they use.


And thirdly, is there any way to have the "summer fan" I wired in - have it kick in at a certain tempurature or certain time of day...then I wouldn't have to wake up and manually turn the summer fan on.

Thanks!
Would need a timer to do it.
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Old 06-19-2011, 02:30 PM   #7
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Old A/c unit tied into new furnace...any problems?


The cold air i assume is coming from 2 pipes tehy drilled to the outside of the house, the cold air returns I cut in are to allow basement air to circulate to the upstairs.

I have read about the Honeywell 8000 series thermostat that allowes you to set the fan speed to auto or on at certain times during the day...I was thinking of buying this and then setting the fan only to run in the morning to cool off the house before we get up.


Thanks for your info as I am a beginner on most of this HVAC stuff!
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Old 06-19-2011, 03:00 PM   #8
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Old A/c unit tied into new furnace...any problems?


That stat doesn't control fan speed. It can be set to On, Auto, or Circ. Circ wil bring the fan on every 36 minutes if it has done a heat or cool call in that time period.

The humid air in the combustion intake pipe is what will condensate in the furnace heat exchanger.
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Old 06-20-2011, 12:15 AM   #9
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Old A/c unit tied into new furnace...any problems?


Quote:
Originally Posted by beenthere View Post

The humid air in the combustion intake pipe is what will condensate in the furnace heat exchanger.
I'm not sure what pipe you mean? Is this the pipe that comes from outside?

I don't see how circulating colder air from the basement would cause any condensation or troubles, just moving air around right?
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Old 06-20-2011, 12:20 AM   #10
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Old A/c unit tied into new furnace...any problems?


If your furnace has 2 PVC pipes going outside. One is the combustion air intake, the other is the exhaust.

How cold is the basement?
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Old 06-20-2011, 12:47 AM   #11
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Old A/c unit tied into new furnace...any problems?


basement is just cool, not cold...but when I run the fan it circulates the air and the upstairs is definetly a lot nicer!
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Old 06-20-2011, 04:06 AM   #12
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Old A/c unit tied into new furnace...any problems?


Ok, should not be a problem them.

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