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viessman cm2

spacecadet
spacecadet Member Posts: 4
in Gas Heating
We have a new viessmann cm 2 311 that is locking out with a f4 fault. Most of the time it will light and run on 3rd try, but if it doesn't light on 3rd try it locks out. Gas pressure and combustion are both perfect, Flame rod and electrode where replaced,

Comments

  • CMadatMe
    CMadatMe Member Posts: 3,086
    Check condensate. How do you know gas pressure and combustion are perfect if you can't get it to light? Strongly suggest you call the person that installed it..

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  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,214
    Natural gas or propane? You may need to open the combustion chamber and look inside to check the condition of the burner and see if there is any debris in the chamber.

    Pour some water through the heat exchanger to see if it drains well.

    Check to make sure you're getting plenty of combustion air.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • spacecadet
    spacecadet Member Posts: 4
    The cm 2 is on propane and will run after a couple of restarts. Opened boiler and it is spotless. Combustion air is from large boiler room with a exhausto that keeps it slightly positive. Boiler is vented straight up with Centrotherm. Draft is with in specs.
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,214
    Have you called Viessmann technical support? They are very helpful.

    (888)484-8643
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
  • mars_6
    mars_6 Member Posts: 107
    What is the elevation where the boiler is installed? There are codeing changes that need to be made depending on the elevation.

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  • spacecadet
    spacecadet Member Posts: 4
    Boiler is at normal elevation. Viessmann tech.support has been very helpful ,but they are also scratching their heads.
  • mars_6
    mars_6 Member Posts: 107
    Have you spoken to Greg McNiell in teck support he is one of the best when it comes to CM2 boilers, Chris who posted above is also very good. I have a CM2 311 at 6800' elevation that will infrequently kick a F9 fault code. New install everything to spec, Quite annoying.

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  • Tim McElwain
    Tim McElwain Member Posts: 4,642
    Do you have the Service Instructions and if so have you gone through them? Has a combustion test been done with a combustion analyzer?

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