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gas valve on slant fin

sesameking Member Posts: 4
I had a Slant Fin Gas Boiler (Concept 21). Beginning in November we were having an issue where in extreme cold temps (below 20 outside) we would hear a whistle going from the boiler thru the exhaust and outside vent - could hear it outside. I had several plumbers come and could never find anything wrong - heat and hot water always worked (but of course it was not whistling at the time because it would normally be overnight or very early in the morning). Long story short, come to find out there were levels of CO emitting and we never knew it. There were corroded spots in the flue and also a rusted hole in the heat exchanger. We ended up getting a whole new heating system put in.

My question is this. We had a plumber put a new gas valve on the boiler in November. It was right after that that this whistling began. Does a new gas valve need any adjustments? Could not adjusting the pressure cause the heat exchanger to rust out?


  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Is the new gas valve

    on the Concept 21 or some other boiler? Your posting is a little confusing. What do you have now for a boiler and what is the make and number of the gas valve? Is this a Modulating/Condensing boiler?
  • sesameking
    sesameking Member Posts: 4
    gas valve

    Hi Tim

    I'm referring to replacing a gas valve on the Slant Fin Concept 21. It was replaced in November and since that time we had a lot of issues w/the boiler - causing us to ultimately have to replace it entirely.

    Does a new valve on the Slant Fin Concept 21 (CB-135) need any adjustments?
  • Tim McElwain
    Tim McElwain Member Posts: 4,480
    Yes the

    boiler should be set up in accordance with Slant Fin instructions. They can be found at

    How is you system vented?
  • sesameking
    sesameking Member Posts: 4
    gas valve

    Vented outside about 10 feet away thru stainless exhaust pipe. So my question is when one installs a new gas valve on the Concept 21 boiler, do specific adjustments need to be made? I'm curious because none were and immediately following its installation we began having heating problems which ultimately led to corroded holes in the exhaust, a hole in the heat exchanger and leaking CO.
  • RobG
    RobG Member Posts: 1,850
    Slant Fin

    Is your boiler connected with black iron pipe or corrugated stainless steel? Gas appliances with CSST or a flex connector will sometimes howl because of the piping. It can be corrected. And as Tim stated, it does need to be set up per the manufacturers instructions. What water temps are you running?

  • sesameking
    sesameking Member Posts: 4

    We no longer have this boiler. The heat exchanger had a hole burnt thru it. These issues began after the new gas valve was installed. So I am basically trying to find out whether the installation of the new gas valve could have caused such issues.
  • MolonLabe
    MolonLabe Member Posts: 1
    I too have a concept 21 that will whistle from time to time.

    It's about 14 years old. This is my first winter in the house so I don't know any of the history on it except I replaced the igniter last night for the second time. The first time was on thanksgiving morning.

    Luckily I ordered a replacement igniter, I wa snt expecting this one to go out so soon again.

    Could be because my heat shield on the igniter is about shot?

    Anyway, I use it for hot water and to heat the water for the radiant floor heating.

    Should I just replace this boiler with something newer and more efficient?

    Doing searches it seems this boiler is rife with problems.

    Thank you.
  • Ironman
    Ironman Member Posts: 6,560
    You've tagged on to the end of an old thread. You should start a new one to get better exposure and more replies.

    There's a lengthy discussion on the "main wall" right now about harmonic combustion noise in a Lochinvar WH055. It's common to a lot of boilers that use negative pressure gas valves. You'll find a lot of info in that thread.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.