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Viessmann Vitodens 100-W: Radial Fan Air Intake Port Deteriorating / Wearing

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WoodsCourtHeating
WoodsCourtHeating Member Posts: 1
edited January 11 in THE MAIN WALL

Hi Viessman Experts,

We have a Viessmann Vitodens 100-W propane furnace and the Radial Fan NRG118 air intake port deteriorates to the point where it drives F4 errors and has to be replaced. Also noticed fouling on the it's burner interface flange. Seems like the burning propane flame is somehow backing down the input channel which I can't imagine is intended. Please see the photo's below.

Any thoughts on why this is happening would be greatly appreciated, we are now on our 2nd fan replacement in 6 years!!!

Thanks, Paul

Radial Fan Intake Port.JPEG Radial Fan Flange.JPEG

Comments

  • gibbs05
    gibbs05 Member Posts: 8

    Just worked on one today with same issue. Code F4 I'm a 4 year old boiler. Wont ignite. Inlet looks the same. Is replacing fan only option? Trying to see what caused this

  • GGross
    GGross Member Posts: 1,720
    edited December 10

    @gibbs05

    It's flue gas recirculation. the flue gasses are re-entering the cabinet and being sucked in to the fan. From my estimation that is really extreme. I've seen at least a hundred jobs where there is considerable flue gas recirc on these boilers and never seen the venturi wear down like that, seen plenty of the "paper" style venturis break down. In the bottom left of the inside of the cabinet there is probably a big brown or black spot like rust sort of. The cure is to separate your vents, the intake should be pulling in fresh clean air only and be separated from the exhaust, not just to manufacturers minimum separation it needs to be separated enough that it doesn't recirc.

    If you really think it's the flame getting sucked out of the fan you can always pull the burner and have a look. My guess is that its not pretty in there! The burner should get pulled out and everything cleaned and put back to factory spec annually (every other year realistically.)

    kcopp
  • gibbs05
    gibbs05 Member Posts: 8

    So the boiler was plugged into a receptacle for a near by humidifier. That plug only had power when the furnace blower was on. So power was getting cut mid heat cycle and flue gasses just hung around in the fan and cabinet and ate away at the venturi. Replaced fan and ran a cord to a proper receptacle

  • gibbs05
    gibbs05 Member Posts: 8
    1000026565.jpg
    GGross
  • gibbs05
    gibbs05 Member Posts: 8

    No post fan purge. It is a one pipe vent system.

  • R Mannino
    R Mannino Member Posts: 441

    It's flue gas recirculation. Check the condensate drain where it goes into the trap. If there is any debris at that connection it might leak flue gas.

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