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Thread: Questions about fresh air return for gas furnace

  1. #1
    DIY Junior Member sanrico's Avatar
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    Default Questions about fresh air return for gas furnace

    Hi all, I have a 2,000 square-foot ranch-style home in a dry climate (New Mexico). The furnace is gas (Bryant Plus 90) and located in the garage.

    There are two fresh-air returns: one in the hallway about 30 feet from the furnace, and one in the living room just on the other side of the wall where the furnace is located.

    The furnace heats well, but it's pretty loud and when it kicks in, the fresh-air return in the living room makes a lot of noise, nearly drowning out the television and conversation. There have been times when we are watching a movie when the furnace is too loud, so I put a piece of cardboard in front of it to quiet it down a little. I figured that it can draw from the other return just for that short period of time.

    My question: Can the fresh air return in the living room be moved to the garage space? I don't know if the colder air will make my heater less efficient, or if I'm violating some sort of code.

    Thank you in advance for your input!


  2. #2
    Jack of all trades DonL's Avatar
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    If your garage is not heated then that is not a good idea.

    You might want to consider a different type of air filter.


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  3. #3
    DIYer, not in the trades LLigetfa's Avatar
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    No, you cannot draw return air from the garage. BTW, it is called a cold return. Fresh air should be coming from outside, also known as make-up air.

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    DIY Junior Member sanrico's Avatar
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    Thank you both for your quick replies. I really do appreciate your knowledge and willingness to help. This forum has been a great help to me over the years.

    I have one more question. Don, you said:
    Quote Originally Posted by DonL View Post
    You might want to consider a different type of air filter.
    Would a different type of air filter on the cold return (thanks LLigetfa for that clarification) make it quieter? The "whooshing" sound from the return is loud enough to surprise guests when the heater comes on.

    Thanks again!

  5. #5
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by sanrico View Post
    Thank you both for your quick replies. I really do appreciate your knowledge and willingness to help. This forum has been a great help to me over the years.

    I have one more question. Don, you said:


    Would a different type of air filter on the cold return (thanks LLigetfa for that clarification) make it quieter? The "whooshing" sound from the return is loud enough to surprise guests when the heater comes on.

    Thanks again!


    I have noticed that some air filters do damper the noise more than others. It is a buy and try tho.

    Dirty filters can cause more noise also.

    You may want to see if you can lower the Blower speed on your unit, some units will have different blower speeds available. Depends on the make and model.


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  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    The returns may not be sized properly. Plus, often they are hard connected and can transmit more noise than they should. If it is just air movement that is your issue, it may be either the size or the fan speed. Somewhere in the documentation, it should state with the BTU output of the furnace, what the fan speed should be. If you can lower it, it will be quieter, and may save a little in electricity, too. You should never go lower than the spec sheet says, though.

    If it is vibrational noises transmitted in the ductwork, most furnaces specify a flexible connection between the furnace and the ductwork. This prevents any vibrational noises from radiating into the metal ducts. This is typically a vinyl covered section of canvas between two sections of ductwork to provide a mechanical break between the two metal parts.

    FWIW, ideally, unless you have a very open floorplan, each room should have a return. Think of it this way...the furnace blower tries to blow hot air into the room...if there's no way to get air out of the room back to the furnace, it can't heat that up. If the room is quite tight, it may not be able to blow any hot air in, either. You want a nice balanced flow - hot air in, cold air out. As a result, the cold air returns are usually down low, and the hot air supply is up higher. In the summer, when running a/c, ideally, their location is reversed...pull the hottest air out at the ceiling, and drop cold air in and let it fall down, cooling the whole room without stratification.
    Jim DeBruycker
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  7. #7
    Jack of all trades DonL's Avatar
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    Quote Originally Posted by jadnashua View Post
    The returns may not be sized properly. Plus, often they are hard connected and can transmit more noise than they should. If it is just air movement that is your issue, it may be either the size or the fan speed. Somewhere in the documentation, it should state with the BTU output of the furnace, what the fan speed should be. If you can lower it, it will be quieter, and may save a little in electricity, too. You should never go lower than the spec sheet says, though.

    Very good Jim.

    It is very important to read the manual when changing Fan speed.

    The Duct temperature will rise, but can save money if the unit supports the speed change.

    Chances of having a return in every room is rare, unless you have a basement.

    Most systems have undersized returns for cost savings.


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