Ductwork size


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Old 03-08-04, 09:01 AM
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Ductwork size

I am planning to improve my heating system. We have 5 warm air ducts (6") in the attic going to registers located high up on the interior walls near the center of the house, and one big, short return. I plan to run new warm air ducts through the basement to new floor registers located near the outside walls. A heater guy said I should use the existing warm air ducts as return ducts. Can I do that or are the 6" ducts too small to be used as returns?
 
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Old 03-08-04, 12:13 PM
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Well you dont say what load you have there how much heat and AC Are you going to be working on. Heat runs on or in the center wall work good for the return air in a home. Do it all the time in older homes. You say 5--- 6" runs thats only say about 500 cfm so just a little bit over a ton of AC . You need about 400 cfm per ton of AC. You could have them come back into that one big return you have and cut it down a little bit. ED
 
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Old 03-08-04, 03:00 PM
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I have an 80,000 Btu/hr furnace, no air conditioning (no need around here). There is no cfm listed on the nameplate.
 
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Old 03-08-04, 03:33 PM
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model number will show furnace airflow or "drive" as we call it. you can use a 6 inch for return, just allow 100 cfm per 6 inch pipe, and be sure the total cfm of return is sufficient
 
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Old 03-08-04, 04:11 PM
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Thank you guys for your interest. The furnace is a Day&Night model # 80UA-14, and it is over 33 years old (am thinking of replacing it too).
 
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Old 03-09-04, 04:22 AM
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Is your furnace in the attic or the basement?
For heating only it would be ideal to have the supplies @ floor level and the returns up high.
If the furnace is in the attic how do you plan on getting the duct work into the basement?
What type of duct material are you planning on going with?

33 years old! Good life, about time for the Smithsonian.
 
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Old 03-09-04, 09:50 AM
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The furnace is in the basement. Does the model number (80UA-14) indicate how many cfm's it puts out?
 
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Old 03-09-04, 01:04 PM
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i am guessing the 14 indicates 3.25 tons, 1400 cfm
 
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Old 03-18-06, 07:56 AM
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couldn't the 14 also be a seer rating? I didn't notice how old the original post said the system was, but I know most newer systems include a seer rating somewhere in the model/serial number...
 
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Old 03-19-06, 01:57 PM
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Originally Posted by 1920_FL_Bungalo
couldn't the 14 also be a seer rating? I didn't notice how old the original post said the system was, but I know most newer systems include a seer rating somewhere in the model/serial number...
it's a 33 year old furnace. maybe close to 65% eff. if guessing.
SEER is the a/c rating. he doesn't have a/c.
 
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Old 03-19-06, 08:37 PM
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80,000 BTUs and 33 years old is anybodys guess. I would bet you have at least a 3 ton drive. Definately not 4 so 3.25 sounds good.
 
 

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