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  1. #1
    Join Date
    Jul 2008
    Posts
    9

    Hmm How quiet should a new Ruud furnace be?

    I have a new 90% + furnace and there is a constant hissing/static noise in the ducts.

    The hissing noise is coming from the heat exchanger of the gas furnace of the new unit. With the unit off and listening in the ducts a light tap on the exterior of the furnace unit leads to a metalic vibration sound that fades away in a couple of seconds. I imagine when the fan is on this vibration is amplified a great deal. The sound is louder as the fan speed goes up.

    The contractor says nothing can be done to stop this sound in the heat exchanger, it is normal. Is it?

    They want to start duct modification to damper the sound, I don't plan to go this route as we can hear the hissing in five to six ducts. Are there quiet high efficiency furnaces out there?

    Thank you

  2. #2
    Join Date
    Mar 2005
    Location
    burlington county n.j.
    Posts
    9,748
    heat exchanger noise when blower is running is not normal in any furnace that i have seen.

    if he cannot correct it find another dealer or have them get a factory rep to come out.

  3. #3
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,244
    Probably isn't the heat exchanger, probably just noise from too much air through undersized duct system. New furnaces move a lot more air than oldies of the same capacity, so if the furnace is oversized and/or the ducts are undersized, you will have noise. What's the model # of the furnace? What size A/C do you have?

  4. #4
    Join Date
    Mar 2008
    Location
    Central Maryland
    Posts
    246
    Quote Originally Posted by JPinMo View Post
    I have a new 90% + furnace and there is a constant hissing/static noise in the ducts.

    The hissing noise is coming from the heat exchanger of the gas furnace of the new unit.
    Go outside to the exhaust , and smell for gas.

    Quote Originally Posted by JPinMo View Post
    With the unit off and listening in the ducts a light tap on the exterior of the furnace unit leads to a metalic vibration sound that fades away in a couple of seconds. I imagine when the fan is on this vibration is amplified a great deal. The sound is louder as the fan speed goes up.
    Was your unit converted from updraft to side mount? If so, they may not have secured the blower assembly properly.

    Quote Originally Posted by JPinMo View Post
    The contractor says nothing can be done to stop this sound in the heat exchanger, it is normal. Is it?
    Perhaps with their customers it is normal. With my Rheem mod furnace, which is just a Ruud with another name, there is no hiss to speak of.

    -HF

  5. #5
    Join Date
    Jul 2008
    Posts
    9
    All the static pressures have been checked and fall into the acceptable range. The ducts seem appropriate for the unit. The furnace model is UGFD-12 Ruud and it it a 5 ton a/c. The hissing corresponds to the fan speed.

    If this heat exchanger design is noisy, I am ready to try another brand. Are they all designed the same or are there some differences?

    Thanks to all of you.

  6. #6
    Join Date
    Sep 2005
    Location
    Atlanta GA area
    Posts
    21,286
    UGFD 12 is a BIG furnace. Could you tell us a little about your home? Also, what part of the country are you in (I may have missed that, as I cannot see that part of the posts while in the reply screen). Things like SQ/FT, one level or two level, number of rooms on this system, any big great rooms, etc etc etc... Also please tell us how many returns there are, and roughly what size the returns are at the furnace. The filter size(s) would be helpful also. What would really help is if you could take a few digital pictures and post them; pictures of the furnace/coil installation including the ductwork at each end. Please be very detailed on this; the more details, the easier for us pro's to help as we can, THX!
    GA-HVAC-Tech

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  7. #7
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,244
    We've installed probably 100 of various Rheem/Ruud 90s of that design. Sis got a test furnace back in 1993. Never had that issue so likely a defect in your particular unit or an airflow noise. On this one, return air should come in 2 sides or the bottom. Is the board giving any error messages like 66, which is unable to move enough air?

  8. #8
    Join Date
    Jul 2008
    Posts
    9
    Here is some additional info... it is a big house, basement and two stories and we live in SW Missouri. The contractor did a load calculation with all the numbers that you are asking about, I will look them up. I believe the system is sized right for the house. I am working on the pics.

    The unit is set up with two big returns coming into the bottom sides of the unit and the fliters are about 10"x20"x2".

    At times the 66 code does flash on the board, just on hot days it seems; otherwise I see a F or C or c

    The slight rattle coming from the furnace/aux. heat exchange area into the ductwork is the thing that appears to me to be creating the hissing noise. They did change out this heat exchange with another new one, but the noise remains. Another contractor from a York dealer indicated to me that the basic design of the high efficiency furnace exchangers are all about the same-- is that the case?

    If we convert the most noisy ducts to new 8" flexduct will that work to damper the hissing?

    Thanks again

    JP

  9. #9
    Join Date
    May 2000
    Location
    Indianapolis, IN, USA
    Posts
    34,244
    How many filters? Need at least 3 for 5 tons in my opinion.

    Seeing 66 error code means the motor can't move the air you are asking for. That means a very restrictive duct system. He better do more investigating to see what can be done to improve it for efficiency sake if nothing else.

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