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Furnace Question

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  • Furnace Question

    I had a furnace replaced in one of my units, small one bedroom second floor apartment. Changed out a 35 year old 65,000 btu Coleman for a 65,000 btu Goodman. The furnace is cycling properly, but the tenant is complaining of cold air when the furnace turns on, she is about 65 years old, but she has a point, the air is quite cold when the furnace starts up. Would it help to insulate the pipes in the basement to help with heat loss; will this lead to condensation? Also, should be furnace motor speed be slowed to help with this problem? The blower motor has what appears to be 2 speeds to select based on the wire that is plugged into the mother board.

  • #2
    Re: Furnace Question

    The new furnace may be oversized for a 1 br apartment. The effiency of the new furnace is at least 80% and the old one is probably around 60%.
    Plus the new furnace most likely has a 3ton drive. Which means it will handle a 3 ton AC unit. I would use the lowest blower speed tap which in most cases is the red fan lead.

    I use 50K btu input furnaces for 1&2 BR units. It's the smallest size I can get from our supplier.

    Hope this helps

    James

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    • #3
      Re: Furnace Question

      The old furnace was rated at 48,000 btu output, which would be about 74 % efficiency. (?) The building is plaster on brick with no insulation, with double pane single-hung vinyl windows, so I didn't think it would be too big. I will check on the lower speed fan, I know this one has a lot more air output than the old one did. Any advice on insulating the pipes in the basement? Will this cause me any problems down the road?

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      • #4
        Re: Furnace Question

        Originally posted by nkyrental View Post
        The old furnace was rated at 48,000 btu output, which would be about 74 % efficiency. (?) The building is plaster on brick with no insulation, with double pane single-hung vinyl windows, so I didn't think it would be too big. I will check on the lower speed fan, I know this one has a lot more air output than the old one did. Any advice on insulating the pipes in the basement? Will this cause me any problems down the road?
        As for the "pipes" do you mean the air ducts? If so it wouldn't hurt to insulate them.

        I'm a little surpised the installer didn't check the fan speed and the temp. rise across the heat exchanger.

        James
        Last edited by James P; 12-22-2009, 07:13 PM.

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        • #5
          Re: Furnace Question

          The new furnaces blowers are controlled electronically now so the blower tends to come on a little sooner than the old style 4064 fan limit switches did.
          sigpic

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          • #6
            Re: Furnace Question

            New furnaces control blower cut-in and cut-out with a timer circuit. Have your installer come back and adjust the DIP switches on the board for a longer cut-in time, say 90 to 120 seconds instead of 30-60 seconds. This will allow the furnace to come up to a higher operating temp before the blower starts, giving you warmer air output at the register on startup. This is a very common complaint with older people, they don't like cool drafts at all. You will loose a little bit of efficiency from the furnace, but a happy tenant is worth it.

            Randy

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            • #7
              Re: Furnace Question

              Originally posted by truckinu View Post
              New furnaces control blower cut-in and cut-out with a timer circuit. Have your installer come back and adjust the DIP switches on the board for a longer cut-in time, say 90 to 120 seconds instead of 30-60 seconds. This will allow the furnace to come up to a higher operating temp before the blower starts, giving you warmer air output at the register on startup. This is a very common complaint with older people, they don't like cool drafts at all. You will loose a little bit of efficiency from the furnace, but a happy tenant is worth it.

              Randy
              I don't think the Goodman furnaces have the blower on delay option.

              Most the newer furnaces that I'm familiar with just have the blower off delay option.

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              • #8
                Re: Furnace Question

                No electonically controlled furnace can control the blower on delay that I know of. The old mechanical fan limits could but they don't let you now for safety. You'll need to ensure the ducts don't blow on her favorite chair. Maybe use deflectors they sell at the Depot. Cold duct work can be minimized by leaving the fan in the on position but the draft would less cold but cool all the time.

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                • #9
                  Re: Furnace Question

                  Originally posted by rjm78 View Post
                  No electonically controlled furnace can control the blower on delay that I know of. The old mechanical fan limits could but they don't let you now for safety. You'll need to ensure the ducts don't blow on her favorite chair. Maybe use deflectors they sell at the Depot. Cold duct work can be minimized by leaving the fan in the on position but the draft would less cold but cool all the time.
                  Don't quote me on this. Back in the early 90's I installed some ICP Comfortmaker furnaces, and I'm thinking you could set the blower on delay. I think they only gave you a 30 or 45 sec choice.

                  James

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                  • #10
                    Re: Furnace Question

                    there has to be a time delay so the fan does not come on until the unit can fire up a little
                    im not up on this unit so i would have the installer come back and look at it and show you whats up
                    Charlie

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                    • #11
                      Re: Furnace Question

                      Originally posted by HVAC HAWK View Post
                      there has to be a time delay so the fan does not come on until the unit can fire up a little
                      im not up on this unit so i would have the installer come back and look at it and show you whats up
                      You are correct. Most are set @ 30 seconds. Which is plenty of time if your blower speed isn't set to gale force winds.
                      The Goodman furnaces factory blower speed for heat is set for Med High.

                      James

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