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Triangle tube Challenger Combo

RDH007 Member Posts: 4
Having issue with my appliance after replacing whole house water filters. Done the same procedure probably 40 times since installing the unit. Had to shut off and purge air from hot / cold lines before restarting. This time unit did not recognize when hw faucet was closed and kept registering temp as if line still open. Didn’t realize until knocking sound was coming from piping - turned off immediately (perhaps 5-8 seconds). Unit will work normally if hw faucet on, but turn off and within I’d say 20 seconds knocking (not loud like water hammer but still extremely concerning) commences. I’d like to think it’s the DHW Sensor malfunctioning but I thought it should immediately create a fault code. Any help greatly appreciated - anyone know a good tech in my neck of the woods (south shore Massachusetts).


  • pedmec
    pedmec Member Posts: 718
    sounds like the water is flashing to steam because its not moving water thru the heat exchanger and the burner is still on. flow switch might be stuck closed but that's just an educated guess as you probably should get a tech there. you really can get yourself in a bad situation if that's the case
  • kcopp
    kcopp Member Posts: 4,189
    On the entrance to the Cold water there is a flow switch. Sounds like the switch got some sediment in there and it will not close.
  • RDH007
    RDH007 Member Posts: 4
    That did the trick! Much appreciated. I’ve become so used to this unit running without problems that I’ve put off the annual general maintenance requirements - won’t make that mistake again. Thanks for taking the time to address my issue. If anyone knows any tech in my area I’d still be interested in sending business his way - even if it’s just for an annual maintenance call.
  • Zman
    Zman Member Posts: 7,447
    I am not sure how far off the cape they go or exactly where you are located. These guys have worked on my Mother's house and I have been very pleased with them.
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • RDH007
    RDH007 Member Posts: 4
    I’ll schedule an appointment and see - Thank you.