Dampers on old potbelly wood/coal stoves

George D · Post by **George D** » Sun. Nov. 14, 2021 8:22 am

I just picked up an Umco 21 coal stove, and will be doing the chimney install soon. I didn't get a flue damper, because It seems a lot of users of these old stoves feel the damper will send CO back into the room, being these stoves leak so much. This is a brand new install, and I want to do it right the first time. Any advice is much appreciated. Thanks, George

Sunny Boy · Post by **Sunny Boy** » Sun. Nov. 14, 2021 10:44 am

The MPD (Manual Pipe Damper) come with holes in the cast iron plate, so they never really block off the exhaust when fully closed. They just slow it down with flow resistance.

Your stove would have to have some large air leaks in under the firebed, or your chimney would have to have a poor drafting ability to overcome the resistance of an MPD and back up to cause a CO leak.

The MPD (or a baro) not only help control the fire, it helps keep more heat indoors by slowing the exhaust gas flow which gives it more time to exchange heat to room air.

I ran a pot belly stove much like yours for a few years, both with wood and coal and the MPD helped a lot to control it.

Paul

George D · Post by **George D** » Sun. Nov. 14, 2021 11:16 am

Thanks for the reply, Paul. I do have a large air leak in the ash pan, which I feel can never be made tight. It basically justs "pivots" in a hole at the right side, and just lays down on a small nub on the left side. Any gasketing material I use won't get the compression it needs to do it's job. I attached some photos.

warminmn · Post by **warminmn** » Sun. Nov. 14, 2021 12:12 pm

Tin foil is your friend for leaks but is temporary. Sometimes fiberglass insulation can be packed into a hole too.

Sunny Boy · Post by **Sunny Boy** » Sun. Nov. 14, 2021 12:50 pm

George D wrote: ↑
Sun. Nov. 14, 2021 11:16 am
Thanks for the reply, Paul. I do have a large air leak in the ash pan, which I feel can never be made tight. It basically justs "pivots" in a hole at the right side, and just lays down on a small nub on the left side. Any gasketing material I use won't get the compression it needs to do it's job. I attached some photos.

High temp silicon stove sealer can reduce a lot of any ash door leakage. Wire brush the inside edge the door. Run a bead of sealer around the edge and close the door against some wax paper and let it setup for 24 hours.

The silicon does not have to rely on seal crush to make a good seal, like a fiber glass door gasket does. It just needs to contact the stove base. So, that way there is no gasket spring-back pressure that would pop the ash door off that gravity ramp type door latch.

For the door pivot hook pin hole, you might be able to make a bushing out of metal tubing and press it into the hole to reduce the hole size closer to the door hook pin diameter.

You don't have to get the door to seal 100% airtight - just reducing any leakage it has now will help.

Same for reducing over-fire air leaks above the firebed. But they have the opposite effect with coal as air leaks under the firebed. They bleed air in over the fire, which cools and weakens the draft strength and makes it tougher to get a coal fire going, plus longer to recover the firebed after refueling..

With wood it's the opposite of coal - the over-fire air leaks make it tougher to slow the fire.

Paul

George D · Post by **George D** » Sun. Nov. 14, 2021 4:11 pm

warminmn wrote: ↑
Sun. Nov. 14, 2021 12:12 pm
Tin foil is your friend for leaks but is temporary. Sometimes fiberglass insulation can be packed into a hole too.

I understand that whatever I do will be a temporary fix...these old stoves were never designed to operate efficiently. Thanks for the advice.

George D · Post by **George D** » Sun. Nov. 14, 2021 4:13 pm

Sunny Boy wrote: ↑
Sun. Nov. 14, 2021 12:50 pm
High temp silicon stove sealer can reduce a lot of any ash door leakage. Wire brush the inside edge the door. Run a bead of sealer around the edge and close the door against some wax paper and let it setup for 24 hours.

The silicon does not have to rely on seal crush to make a good seal, like a fiber glass door gasket does. It just needs to contact the stove base. So, that way there is no gasket spring-back pressure that would pop the ash door off that gravity ramp type door latch.

For the door pivot hook pin hole, you might be able to make a bushing out of metal tubing and press it into the hole to reduce the hole size closer to the door hook pin diameter.

You don't have to get the door to seal 100% airtight - just reducing any leakage it has now will help.

Same for reducing over-fire air leaks above the firebed. But they have the opposite effect with coal as air leaks under the firebed. They bleed air in over the fire, which cools and weakens the draft strength and makes it tougher to get a coal fire going, plus longer to recover the firebed after refueling..

With wood it's the opposite of coal - the over-fire air leaks make it tougher to slow the fire.

Paul

I'll give it a try Paul, and I will install a damper. Worst case if it causes me problems, I can always remove it.

Dampers on old potbelly wood/coal stoves

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