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  1. #1

    Loud clacking sound on Carrier Infinity Furance during call for heat

    I've tried researching the topic but have not had any luck and so hoping someone may shed some light on the issue (or hopefully non-issue).

    2 1/2 years ago I moved into our new home which also has a Carrier Infinity furnace. I had an installer add an Infinity thermostat as well. This winter (and last winter) I've noticed that when there is a call for heat, the system goes through it's pre-cycle and then before the actual circulating fan kicks up to a higher speed there is a noticeably loud clack. It occurs frequently and is actually a little annoying (and partially distressing).

    I complained to the builder while we were in warranty, and the tech from the installation company said the noise was normal, yet I've never heard a Furnace make such a noticeably loud noise and I'm a little dubious from previous experience with my builder (and subcontractors).

    If I had to describe the sound, it's almost like a valve slamming shut (or perhaps a large solenoid clacking shut), but I honestly don't know as I'm not a tech. I'm stuck between my paranoia and calling a third party company out only to concur with what the builders company says (spending money) vs. leaving it and encountering a more serious issue.

    As a note, there is an Air Exchanger installed as well that I leave running 24/7 on low and the noise does not occur during the summer with our AC.

    In the end, is it normal for the Carrier Infinity Furnaces to have a louder then usual heating cycle?

    Thanks for any help / input.

  2. #2
    I'm not sure if this is of any value - the clacking sound is noisiest on the second floor through the air return vent in my office.

  3. #3
    Join Date
    Jan 2009
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    Keokuk, IA
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    I'd call a reputable Carrier dealer to come check it out. Its' overall a good idea to have your furnace serviuces anually to check any operating issues before winter.

    My best guess would be it's related to the gas valve and/or flame ignition. The valve itself usually isn't very loud. But the "whoosh" of the flame lighting can be a little noisy, especially if maybe draft is marginal or maybe gas pressure isn't set correctly. My Infinity furnace is in the attic and the only think I hear is the hum/vibration of the inducer fan. I can't hear the flam light-off or the gas valve.

    If it's happeneing jsut before the blower comes on, that's probably the point where the gas valve switches back down to low fire. The furnace always lights off on high stage and then warms the heat exchanger for a short period before turning on the blower and cycling down. FWIM, Low fire with a cold heat exchanger can cause condensation in the primary heat exchanger and draft issues with low air velocity over the cold surface, that's why they start out on high stage wth the blower off. It's similar ot hte reason that your car 's engine runs at a high idle when it's cold.

  4. #4
    Quote Originally Posted by motoguy128 View Post
    I'd call a reputable Carrier dealer to come check it out. Its' overall a good idea to have your furnace serviuces anually to check any operating issues before winter.

    My best guess would be it's related to the gas valve and/or flame ignition. The valve itself usually isn't very loud. But the "whoosh" of the flame lighting can be a little noisy, especially if maybe draft is marginal or maybe gas pressure isn't set correctly. My Infinity furnace is in the attic and the only think I hear is the hum/vibration of the inducer fan. I can't hear the flam light-off or the gas valve.

    If it's happeneing jsut before the blower comes on, that's probably the point where the gas valve switches back down to low fire. The furnace always lights off on high stage and then warms the heat exchanger for a short period before turning on the blower and cycling down. FWIM, Low fire with a cold heat exchanger can cause condensation in the primary heat exchanger and draft issues with low air velocity over the cold surface, that's why they start out on high stage wth the blower off. It's similar ot hte reason that your car 's engine runs at a high idle when it's cold.
    Thanks for the additional information - I pulled the cover off last night to see if I could distinguish what part of the unit the noise came from - naturally it didn't do it. I know what you mean by the condensation, a measureable amount drains out at the beginning of the cycle. Oddly enough it hasn't done it for the last 12 hours - the only difference is that I had turned off the main switch for about 5 minutes last night. Seems like I reset something. I don't think it's the flame lighting because it's a fair clear "clack" sound, like a valve snapping shut. Someone mentioned to me recently it might be the damper?

  5. #5
    Join Date
    Jul 2005
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    5,576
    Could be the air filter pulling to when the blower starts or switches to a higher speed. Check for slop in the filter holder.

  6. #6
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    Sep 2003
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    1,677
    okey dokey

  7. #7
    Join Date
    May 2008
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    Missouri
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    Are you using a pleated (accordian) air filter? If so, switch to the cheaper non-pleated filter and see if the noise goes away. The restrictive filter could be getting sucked against the furnace because of the restrictive filter.

  8. #8
    Thanks everyone for replying.

    1. I am using a pleated accordian filter. It's a 5" filter that was installed afterwards by a Carrier installer

    Two things I noted while listening.
    1. Standing infront of the unit I hear a loud click just before the exhaust fan starts up, though I'm not sure if this is what I hear 2 floors up.

    2. The humidifer is on the cold air return - and that is where I often hear the loud clack. However, I checked the humidifier immediately after I heard the loud clack again and it was not running and the furnance was just starting the heating cycle (so I don't think it was the selinoid shutting off).

  9. #9
    Join Date
    Jul 2010
    Location
    wisconsin
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    270
    Your clacking sound is the humidifier relay energizing, which is probably mounted in the blower compartment. We use a quiet relay called a rib relay, call a reputable company to fix your problem

  10. #10
    Join Date
    Jan 2009
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    I wonder if a section of shweetmetal on the return wasnt cross braked or is otherwise making noise as it pulls inward under the vacuum in the duct.

    I bet a good pro could isolate and identifynthe sound pretty quick. Not much substitute for field experience. I love being in a meeting in a control room talking to someone near a industrial process at work, and suddenly everyone will stop and be like, whats that. Just a shift in a sound or vibration and they know something isnt right. In the really old processes... those installed before even pnematic controls were available, they run some parts of it by sound and feel alone. Lots of settings and adjust,ments are still completly manual and would be almost impossible to automate reliably.


    Sent from my SGPT12 using Tapatalk 2

  11. #11
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,599
    Quote Originally Posted by motoguy128 View Post
    I wonder if a section of shweetmetal on the return wasnt cross braked or is otherwise making noise as it pulls inward under the vacuum in the duct.




    Sent from my SGPT12 using Tapatalk 2
    Oil canning.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  12. #12
    Thanks everyone for the responses. Based on the suggestions and information, I was able to determine a better idea of when and where the loud clunk / bang occurs. I thought as well the humidifier might be the culprit so I disconnected it completely to which no difference was made. When there is a call for heat, the small exhaust fan turns on for about 5-10 seconds. After that, the loud clunk happens. Oddly enough, you can feel it in the floor immediately above the furnace

    Additionally, the clunking dissipates when I do a hard shut off (which I did to disconnect the humidifier) and then comes back a day or so later. This makes me think it wouldn't be oil canning as the hard shut off shouldn't make a difference either.

    That being said, is there some kind of damper or valve that opens / closes at the beginning of a heat cycle? if so, is it something that can go bad and start clanking?

    I truly appreciate the information.

    Regards,

  13. #13
    Join Date
    Jan 2009
    Location
    Keokuk, IA
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    I wonder if the gas line size is marginal (high velocity) and isn't supported well, so when it open, it hammers/vibrated. Anyone seen that happen before?

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