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  1. #1
    Join Date
    Dec 2006
    Location
    Chicago
    Posts
    14

    Gas furnace: Variable speed vs two speed with fan always ON

    My friend just got a variable speed furnace installed and he was very happy that it eliminate some cold spots in his house.

    I have a two-speed furnace. With fan always on it seems not eliminating the cold spot (two room addition on the 2nd floor, always cold w/o inline booster fan ON). It actually gets less comfortable in warm rooms, since the fan circulate cold air when the furnace is not on. I can feel cold air out of the floor vent.

    What is the advantage of variable speed furnace? If the furnace is not always ON, what is the difference? Thanks in advance.

  2. #2
    Join Date
    Aug 2002
    Location
    Office and warehouse in both Crystal River & New Port Richey ,FL
    Posts
    18,836
    Your friend probably has a better designed duct system.Yours may be so far off that with the fan running some rooms are cold before the area with the stat gets cool enough to bring the furnace on.


    Your ducts could be located in a colder area then the friend's.


    His variable speed may also be running the fan on at low or medium speed,so drafts are less noticable.

    You should have a Pro ,do a Manual J and D to see what is needed to get the duct system corrected.

  3. #3
    Join Date
    Jul 2006
    Location
    Lancaster,Ohio
    Posts
    464
    It sounds like your problem is in your duct system and not the equipment. Did they install a return air in each of your new rooms?
    IcyFlame

  4. #4
    Join Date
    Dec 2006
    Location
    Chicago
    Posts
    14
    Yes. I do see return vents up on the wall. I also called the duct cleaning service to clean them up and found no difference. If I leave the doors open, it should act as returns as well, right? The problem is that there is no much air flow from the floor vents in the 2-room addition.

    The inline booster fan I got can be found in Menards. It is noisy and under-power.

  5. #5
    Join Date
    Oct 2003
    Location
    Washington
    Posts
    7,405
    Quote Originally Posted by dash View Post
    Your friend probably has a better designed duct system.Yours may be so far off that with the fan running some rooms are cold before the area with the stat gets cool enough to bring the furnace on.


    Your ducts could be located in a colder area then the friend's.


    His variable speed may also be running the fan on at low or medium speed,so drafts are less noticable.

    You should have a Pro ,do a Manual J and D to see what is needed to get the duct system corrected.


    Your answer is above. Get that booster fan out of there as well. Duct cleaning will not make your ducts perform better. In some instances it will actually hurt because those machines can tear your ductwork up depending on what they use.

  6. #6
    Join Date
    Nov 2005
    Posts
    1,340
    Ductwork! The lost art. Flex duct is bad. No airflow means you need help.

  7. #7
    Join Date
    Nov 2004
    Location
    Naples, Fla.
    Posts
    1,403
    Quote Originally Posted by emoney1971 View Post
    Ductwork! The lost art. Flex duct is bad. No airflow means you need help.
    Flex duct is no worse & no better than any other duct, in fact in terms of noise reduction it's superior. Proper sizing & installation, as with all products is the key.

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