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Heat Activated Draft Control

Drod Member Posts: 59
I've discovered that I have a heat activated vent damper on the flue/pipe going from my boiler to the chimney. I'm assuming it's about 25 years old, and appears to be working fine (CO detector never goes off, and when I've looked at it using a mirror and the boiler is running the "wings" are opened about 30-40%). Should I be checking it regularly, or doing any maintenance work on it?
Thanks in advance.


  • Steamhead
    Steamhead Member Posts: 14,338
    That's probably an old AmeriTherm

    I have one of these thermally-activated units on my water heater and it has held up well. But like any stack damper it should be checked periodically. This is best done by a technician with proper tools and instruments, as part of a yearly inspection- go to the Find a Contractor page of this site to locate one near you.

    Unfortunately, this type of damper is no longer made as far as I know. If it goes bad, I'd replace it with an electrically-operated one.

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  • The AmeriTherm thermal dampers

    are not made any more. If it is working leave it alone. I have had one on my water heater for over 20 years. I check it about once a month when I ma in the basement and it is fine. Good idea to have a combustion test run about twice a year other than that it should be fine. If it is the Ameri-therm it was the only one the gas company I worked for would approve. I ran tests on all the thermal dampers made in our lab and that one was the only one that opened fast enough and closed fast enough. All the rest took too long to open and stayed open too long to be any good as far as efficiency. The other thing about Ameri-them was the four bi-metal quadrants, that way if one got stuck or broke the others would still open making it much safer than the single opening style.
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