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Loud snap when furnace turns on and off

TronTron Member Posts: 2
I've got a 10 year old Rheem gas furnace. I just had an HVAC tech out to do the regular cleaning and maintenance and he gave it a good bill of health.

2 weeks later I turn it on for the first time and every time it turns on or off, there is one loud snap. I can even hear it on the first floor of my home. I assumed it was the igniter, but it happens when the heating element turns off too....and I can't figure out what would cause it as it shuts off. It's not a bang. More of a sparking snap sound. And it never happens more than once per start or stop.

Any suggestions? Ill admit I'm not much of a do it yourself guy, but I like to be somewhat educated when dealing with contractors...


  • JackJack Member Posts: 936
    I think they are designed that way to....

    Number one give you the satisfaction of knowing that the heat is on and you will be warm. Secondly, it does so on shutdown to give the the knowledge and comfort that the unit is off and not consuming any more energy. See, it is all in how you look at it.

    I've always described it as, Kawumpf...heats on! And then, Kawumpf...heats off

    Beyond that I cannot say as I'm not sure how the Rheems are set up.
  • RolandRoland Member Posts: 147
    Loud Snap.........

    I had a water heater that made a similar sound. It was the gas valve opening and closing.
  • TronTron Member Posts: 2
    thanks, guys.

    I didn't think it could be too serious since i just had someone out to look at it and all was fine. But, this is my first winter in this house, so this furnace (and it's noises) are all new to me. My last home's furnace didn't make this sound, but it was a different brand, too.
  • JStarJStar Member Posts: 2,668
    edited October 2013

    My bet is that you are hearing a small relay click on and off. If the relay is attached to the furnace case, they can make a loud sound.
    - Joe Starosielec
    [email protected]
  • BobCBobC Member Posts: 4,408
    gas valve

    When my Carlin EZ-Gas was first installed last October it had a loud noise at the start and end of firing that I traced to the gas valve being turned on and off. It was very noticeable in the living room above.

    I found the valve was transmitting the noise up the 3/4" gas line that was tightly clamped to the floor joists above. The solution was to wrap the pipe in some silicone rubber sheet and then put the clamp back in place but not as tight as it was. That cut the valve noise by at least two to one.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • Ron Jr.Ron Jr. Member Posts: 527
    I think it's a relay too

    Some manufacturers use isolation relays that sound like those snaps your kids throw at the ground to make em pop !

     Bob could be right too , I've heard some loud gas valves open and shut too . 
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