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Old 10-23-2010, 07:22 AM   #1
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AC backdraft dampers?


New 3 ton two stage with variable speed handler w/ AccuClean in unheated third floor attic. 5 supplies second floor, return top of stairs second floor and 4 supplies first floor --all cieling mounted with insulated round ridgid or flex duct-- AC only -- house heated by hydronic baseboard. Question--- does the AC system need backdraft dampers. I am thinking about heat loss to unheated handler in attic thru supplies and return during heating season. Home is located in Boston, Mass area. THANKS

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Old 10-23-2010, 07:34 AM   #2
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AC backdraft dampers?


IMO I would leave it and allow some heat into the unit to prevent it from getting too cold and rusting the circuit board and VERY expensive motor etc. I would turn the fan to ON occasionally to circulate some air thru it and keep it dry. Corrosion is a VERY expensive and serious issue with high end expensive units and can cost $1000s to fix.
You have a very efficient energy saving ECM motor which only uses 80 watts on low speed so you may want to leave it to ON for circulation if your unit is setup for that. Contact the installer or post the model and make here for more info.

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Old 10-23-2010, 11:36 AM   #3
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AC backdraft dampers?


Down here. Its common for people to put a piece of cardboard in the return to stop air from flowing intot eh duct work and unit. This prevents the humid air from the house from condensating in the ducts and on the cold motor. Some people buy a new air filter, and leave the plastic on it and install it in the return air filter grille.

Every so often. Someone does forget to open the return in the spring though.
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Old 10-23-2010, 12:11 PM   #4
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AC backdraft dampers?


I wonder if even a small amount of moisture sneaking past the cardboard blockage would condense on the motor. I have seen a LOT of damage/circuit boards turn green and connections fail/motors fail from corrosion in damp cold basements. My preference would be to keep some air flowing thru it.
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Old 10-23-2010, 12:20 PM   #5
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AC backdraft dampers?


Down here. Its the warm moist air flowing through it that causes the corrosion. This is for units in the attic. Been to places. that the people didn't block off the air. And every duct had water in it.

In a basement, or crawlspace. Its the air leakage of the duct system that causes moisture to be pulled in. As the warmest air in the duct rises to the occupied area, its replaced by basement/crawlspace air.
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Old 10-23-2010, 12:22 PM   #6
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AC backdraft dampers?


Quote:
Originally Posted by yuri View Post
I wonder if even a small amount of moisture sneaking past the cardboard blockage would condense on the motor. I have seen a LOT of damage/circuit boards turn green and connections fail/motors fail from corrosion in damp cold basements. My preference would be to keep some air flowing thru it.
You guys are smart up there. And don't put A/C units in the attic, do you.
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Old 10-23-2010, 05:10 PM   #7
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AC backdraft dampers?


Too da*mn cold up there for furnaces. A few houses with h/w heat have air handlers with AC but no furnaces up there.

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