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Gas vent dampers

I am a Licensed Plumbing and Heating contractor located in Rhode Island.
Recently a problem with a vent damper on a boiler that I installed some two to three years ago reared it’s ugly head again.
Upon installation I left the vent damper switch in the normal position.
Just after the year warranty had passed a no heat call came. The vent damper was found to be faulty. I replaced the vent damper. The only thing I did different. Hoping to avoid this same no heat call in the future, was move the switch on the damper to hold open. Heat was fine and client paid the bill. OK good.
The other day. ( which is again just after warranty of the newer vent damper.) A no heat call came in. The problem is not the vent damper. The dampers wire harness has a slightly broken wire near the boiler control and the boiler fails to operate. In the morning the client pushes the cover of the L8148 in and low and behold the heat comes on.
At this point I have removed the cover of the Honeywell L8148 taken the wire harness out of its normal entrance to the control box and taped it to other conduits exiting the control. All is good. Just one thing this is not the way it should/shall be left.
I am aware that the L8148 has a fusible link that if you remove the factory plug and use a damper. The fused link burns and you can not use the factory plug again.
The client is not happy!!!! While no fault of my own. This installation has not made it through a season without a problem. All warranty’s are over. My clients do not want to pay for anything the damper, the L8148, never mind me. This is a top of the line boiler with a top of the line installation. The client paid a premium. I expect to provide many years of good quality service when I install something /anything.
This vent damper has been a thorn in my side.
Is there a way to safely by-pass this vent damper and not replace either the control or the damper?
All that being said. I am all for saving energy! Enough is enough these vent dampers have been a problem sense day-one.

Thank you for any and all information and your time.

Russell L. Hill Jr.


  • Steamhead (in transit)Steamhead (in transit) Member Posts: 6,688
    Why not

    just replace the harness? It would take about the same amount of time, and you wouldn't have to modify anything.

    What brand of damper was it that failed so quickly? Some are better than others......

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  • jeff klaverweidenjeff klaverweiden Member Posts: 57
    vent damper

    As far as I am concerned there is not one name brand on the market that has not given me trouble.All the excitement of saving energy goes right out the window when the customer has no heat.If its not the micro switches on the damper assembly its the damper wiring harness. Now I know why installers leave the dampers in open position on a new job
  • pjcpjc Member Posts: 4

    Not to mention that vent dampers on gas boilers are notorious for causing chimney damage. The pinheads who come up with these stupid ideas never cease to astound me. Always leave them open or line the chimney with stainless steel.
  • do not want to give in

    I would change the harness if I had not gone through this all so many times before.
    I don’t feel like giving in to this engineered obsolescence anymore.
    Looking at the paper work at the job and on the webb. It looks like what is needed is a jumper between poles 2 & 3 at the L8148, but I am not totally sure what goes on behind the circuit board, I do not want to burn up anything nor do I want to bypass any safety equipment.
  • Steamhead (in transit)Steamhead (in transit) Member Posts: 6,688
    Haven't seen that yet

    and there are any number of damper-equipped boilers out there.

    I would think that the damper keeps the chimney from cooling down as quickly, since the hot flue gases can't leave the chimney so easily if nothing comes in from the bottom to replace them.

    Do you have pics of these damaged chimneys?

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  • Bob HarperBob Harper Member Posts: 54

    You need to follow the mfrs. lised instructions. If they require a draft hood, then you must install one. If they specify theirs (Weil McLain) you must use theirs. If they spec. an auto vent damper, you must follow the spec. The point is, all our free advice isn't going to cover you in the case of a problem. Given the history, if God forbid something goes wrong and it fails to open.....well, nobody wants that. Better to replace the unit but test to ensure proper operation. Always document your installations with pics. In this case, it would be vital to have a pic showing the relationship of the components, part numbers, and switch position. Vent dampers are nothing to mess around with.

    A chimney should not be relined based upon the presence of a vent damper or not but on a Level II inspection and the class of service.

  • Thanks for Info


    Thanks for your important information. This is not a draft hood this is a motorized vent damper. In my opinion only needed for saving energy. Which I have said I am all for. With a limit.
  • Russell Give me a call

    at 401-437-0557 and I will give you some help.
  • I will


    I will give you a call during reg. Bus hours. I thank you for any help you may give.

  • JohnNYJohnNY Member Posts: 1,811
    Vent damper.

    Vent damper = motor and end switch
    Same as a Honeywell zone valve.
    Identify the power wires to the motor and jump out the other two at the boiler side of the harness. Those are the end switch. This of course is a temporary fix.

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    Or email John at [email protected]
    Or at Gateway Plumbing & Heating
    John travels regularly to out-of-state clients for consulting work.
  • put it to bed


    I wish to put this to bed. I really do thank you for your input. I am not looking for Temp. Fixes.
    There has to be a way!
  • Sent you an e-mail

    for the rest who are interested this is what you can do if you are comfortable with assuming the liability for changing mfrs specs.

    Concerning your problem with the vent damper: If you are going to cease to use the damper then remove it from the flue. Then take the plug on the L8148 control and jump out the two middle terminals/or wire which ever is available in case you have done some change of wiring. All that does is bypass the blown fuse in the L8148. As long as the damper is no longer in the flue you are all set.

    Make sure everyhing works and that the boiler shuts off on limit on all calls for heat.

  • Thank you

    Thanks to all who participated in this fact finding mission of mine. I am sure the procedure that I have been able to find with the help of all of you within the pages of “THE WALL” will take care of the problem and finally put this to bed. At this point all I can say is if you have a heating problem voice it here and you will find the answer.

    Thanks Again

    Russell L. Hill Jr.

    [email protected]
This discussion has been closed.


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