Sealant creating a draft problem?

[Mech]

Hello friends.

I was hoping to get the collective opinion on an issue I’m having with my little wood stove. I’ve sealed some gaps in the panels and stovepipe with stove cement and now the fire seems starved for air.

The heater is a 1979 Atlanta Stove Works “Old Hickory”. Nothing special really, very basic unit. The stove pipe is 37 inches vertical, and elbows to a small straight horizontal section providing about 10 inches to the recently inspected chimney. The chimney is approx... 25 foot masonry construction with no cap.

I had a sight overfire and noticed some smoke escaping between the panels and small gaps in the stove pipe. I sealed these up with cement and performed a flashlight test. Since then, the stove doesn’t seem to get enough air even with the vent wide open. I’ve opened windows to account for room air with no success. The only way I can get the stove to fire well is with the door cracked.

Any ideas? Are these cheap old stoves designed to be “leaky”?

 

[begreen]

Could be other issues that are not related to the sealant. If this is a basement install it might be negative pressure and the chimney is backdrafting, especially when outside temps are mild. Or it could be the chimney tile area is large compared to the stove's flue requirement.

 

[Mech]

Could be other issues that are not related to the sealant. If this is a basement install it might be negative pressure and the chimney is backdrafting, especially when outside temps are mild. Or it could be the chimney tile area is large compared to the stove's flue requirement.

Fair enough point. Thanks. It’s a first floor installation in a 100 plus year old farmhouse. I opened a window about 6 feet from the stove and it made no real difference. I’m puzzled. I’m tempted to blame it on the stove. My wood is mixed variety mostly hardwoods reading about 10%.

 

[begreen]

Fair enough point. Thanks. It’s a first floor installation in a 100 plus year old farmhouse. I opened a window about 6 feet from the stove and it made no real difference. I’m puzzled. I’m tempted to blame it on the stove. My wood is mixed variety mostly hardwoods reading about 10%.

Does the stove have a baffle? If yes is it in correctly?

 

[bholler]

Did you check the chimney after your "slight overfire"? If it was actually a fire it could have expanded creosote in the chimney and caused a restriction.

 

[Mech]

No baffle in the stove at all. It’s a simple affair, firebox on legs. Creosote build is minimal, but I will admit there is a little protrusion of insulation coming from a second floor access plate. I recognize this is an issue and will be adddressed shortly, however it was present previously and the stove fired like a champ.

 

[bholler]

No baffle in the stove at all. It’s a simple affair, firebox on legs. Creosote build is minimal, but I will admit there is a little protrusion of insulation coming from a second floor access plate. I recognize this is an issue and will be adddressed shortly, however it was present previously and the stove fired like a champ.

But did you check everything after the overfire?

 

[Mech]

But did you check everything after the overfire?

Yes, top to bottom.

 

[bholler]

Yes, top to bottom.

Ok good

 

[begreen]

Is there a cleanout door at the bottom of the chimney? Is it sealed tightly? Maybe try duct taping it to ensure a tight seal.

 

[Mech]

Is there a cleanout door at the bottom of the chimney? Is it sealed tightly? Maybe try duct taping it to ensure a tight seal.

No cleanout at all really in the chimney. It appears to be blocked off just below where the stovepipe enters.

Is it feasible that the little tuft of insulation at the scond floor access s disrupting the flow that much? Do these stoves perhaps have a repution for not breathing well?

 

[begreen]

Normally these old timers are not too fussy about draft. Did you look for any obstruction in the air inlet? Can we assume that you are burning fully seasoned wood? If yes, describe the entire flue system from stove to chimney cap, including any turns in the flue piping and the ID of the masonry chimney, and its height.
Pictures are always welcome.

 

[bholler]

No cleanout at all really in the chimney. It appears to be blocked off just below where the stovepipe enters.

Is it feasible that the little tuft of insulation at the scond floor access s disrupting the flow that much? Do these stoves perhaps have a repution for not breathing well?

You really need to plug that other crock with firebrick and refractory cement. They can be very dangerous in the event of a fire.

 

[begreen]

You really need to plug that other crock with firebrick and refractory cement. They can be very dangerous in the event of a fire.

I wasn't sure what is meant by "access plate"

I will admit there is a little protrusion of insulation coming from a second floor access plate

Is this a second hole in the chimney? If it's just stuffed with insulation that's no good. Follow bholler's advice.

 

[Mech]

Here are some images of the air inlet wide open. The wood reads 10% moisture.

The stovepipe exits the rear of the unit and runs 37 inches vertical and elbows. After the stovepipe elbow there is a short 10 inch horizontal run into the chimney. The chimney is 7x7 with no turns. Straight shot to the roof with no cap. It’s 20-25 feet from where the stovepipe enters to the top.

There’s is one very small obstruction at the second floor access where another stove had once entered the chimney. It’s really just a small tuft of insulation but does take up maybe 20% of the cross section there.

This will be remedied shortly by removing it and bricking up the old access.

 

[begreen]

Just a guess here. Fiberglass doesn't block air. If there is a large inflow of air into the chimney past the fiberglass plug that might be diluting draft. That's why I asked about a cleanout.

Wood moisture of 10% is pretty low. Is this being measured on a freshly exposed face of a resplit piece of wood at room temperature and not the end grain? At the pins being pushed very firmly into the wood?

 

[Mech]

A sampling of the wood measured at end grain, split face, through bark, you name it.... 18% absolute max.

 

[bholler]

A sampling of the wood measured at end grain, split face, through bark, you name it.... 18% absolute max.

Was it a fresh split face? If not and you are getting 18% without splitting i would guess you wood is not that dry. But the second crock could be causeing problems with air leakage

 

[Mech]

When I crack the door juuuust slightly it runs just right. This allows about the same amount of air into the box as it has before i sealed it up. I’m confident that sealing the unit has caused my performance issues.

However... it’s very possible that the additional air provided by the leaky box was making up for some other deficiency in the system. Effectively allowing the stove to cheat and overcome some other derogatory factor.

I’ll continue to investigate and please keep the suggestions coming. Thanks!

 

[bholler]

When I crack the door juuuust slightly it runs just right. This allows about the same amount of air into the box as it has before i sealed it up. I’m confident that sealing the unit has caused my performance issues.

However... it’s very possible that the additional air provided by the leaky box was making up for some other deficiency in the system. Effectively allowing the stove to cheat and overcome some other derogatory factor.

I’ll continue to investigate and please keep the suggestions coming. Thanks!

Sealing on the exhaust side would have absoluty no negative effect on your draft. My bet is still on something happening with the system due to your overfire. Can you tell us exactly what happened? Have you checked the second thimble to see if that seal has changed at all?

 

[Mech]

With regards to the sealant, maybe I wasn’t clear in the earlier posts. I sealed up both the firebox and the first section of stove pipe. The newly sealed section in the firebox was right next to the door and was not functioning as exhaust. It was providing additional unregulated intake air to the fire.

The overfire “incident” was slight. It ran hot after I over loaded it and had the door open. It ran hot for maybe 5 minutes and I got some smoke out of the larger cracks in the stove pipe joints. No flue fires or anything like that.

The second floor thimble seems tight and doesn’t suck room air when the stove runs.

 

[bholler]

Oh well that is totally different. That absolutly could have an effect

 

[Mech]

Right, so pursuant to the original question I was getting at are these kinds of stoves meant to be run “leaky”? Or are they known to starve themselves a little?

If not, maybe I have a design problem with the chimney.

 

[begreen]

Right, so pursuant to the original question I was getting at are these kinds of stoves meant to be run “leaky”? Or are they known to starve themselves a little?

If not, maybe I have a design problem with the chimney.

Depends on the stove and age, but most of the good ones were designed to afford proper regulation with the air intake control and not be leaky.