creosote

Hello Everyone!
Thinking about hooking up my Modern Oak 16 this season.
Previous occupant here burned wood for about 30 years and deposited lots of creosote in the approx. 290 year old flues: Forgive the possibly dumb question but is there a high chance of igniting this stuff with an anthracite fire?
Thanks for any advice...
Pete in CT

I think the chance is low, but run a brush in that chimney anyway. The coal heat will probably dry out the creosote and it will flake off and fall to the bottom where it should be shoveled out.

All that creosote will be at the bottom of the chimney in a few weeks.

There is two potential safety issues here. Firstly if you are using a barometric damper if a chimney fire is to occur you have perfect source of air for the fire. If you are going to install a barometric damper hold off until the creosote is gone. For the record I have never heard of coal stove igniting creosote.

The other issue already mentioned is it's going to fall off and it could potentially block the flue pipe if enough falls off at once. Be sure to check the flue pipe frequently. A T at the thimble with one end capped will give you easy access to it for inspection and cleanout. In fact adding T's in place of elbows at appropriate places will give you access to any horizontal runs in flue pipe.

Lastly it's generally recommended you install flue pipe male ends towards the thimble. It's small safety measure but you can't do that with wood because the creosote will run out of joint. No idea if that will happen when switching to coal but it's something to consider.

Richard S. wrote: ↑

Wed. Sep. 30, 2020 6:45 am

There is two potential safety issues here. Firstly if you are using a barometric damper if a chimney fire is to occur you have perfect source of air for the fire. If you are going to install a barometric damper hold off until the creosote is gone. For the record I have never heard of coal stove igniting creosote.

The other issue already mentioned is it's going to fall off and it could potentially block the flue pipe if enough falls off at once. Be sure to check the flue pipe frequently. A T at the thimble with one end capped will give you easy access to it for inspection and cleanout. In fact adding T's in place of elbows at appropriate places will give you access to any horizontal runs in flue pipe.

Lastly it's generally recommended you install flue pipe male ends towards the thimble. It's small safety measure but you can't do that with wood because the creosote will run out of joint. No idea if that will happen when switching to coal but it's something to consider.

I always install the horizontal sections with some slope upwards toward the chimney. With the male ends of the pipe toward the chimney, fly ash will be forever leaking out the pipe joints everytime you shake the stove. Been there and got fed-up with the daily fly ash vacuuming under areas near the pipe.

Years ago, I switched to female ends toward the chimney and no more fly ash seeping out.

I'd love to use T sections for clean-out at every turn, but I can't find T's with the female ends facing toward the chimney when the clean-out cover end is facing the opposite way horizontally to allow getting into the horizontal pipe sections.

Paul

Sunny Boy wrote: ↑

Wed. Sep. 30, 2020 7:42 am

Years ago, I switched to female ends toward the chimney and no more fly ash seeping out.

I have never heard of that issue Paul but it makes sense. Male ends towards the chimney is minor safety improvement because the gas will flow over the joint instead of against it. Female ends towards the chimney is standard install with wood because the creosote will leak out.

but I can't find T's with the female ends facing toward the chimney when the clean-out cover

Cut the crimped section off the flue pipe which may not be viable option if you have already have the pipe sized for application. Of course that will put the male end torawds the chimney but it will only be those joints.

Richard S. wrote: ↑

Thu. Oct. 01, 2020 3:56 am

I have never heard of that issue Paul but it makes sense. Male ends towards the chimney is minor safety improvement because the gas will flow over the joint instead of against it. Female ends towards the chimney is standard install with wood because the creosote will leak out.



Cut the crimped section off the flue pipe which may not be viable option if you have already have the pipe sized for application. Of course that will put the male end torawds the chimney but it will only be those joints.

No safety gained with gas flowing over the joint instead of against it. Remember there's more pressure outside the pipe than inside, or else the chimney has no draft strength. So it's not the same as if you were blowing air over the joint. If smoke leaks out there's a problem with the draft strength. Plus, there isn't as much gas flow velocity near the pipe wall as there is more into the pipe middle. So less Bernoulli effect to keep the heavier than air fly ash from leaking out. If anything, pipe joints leak outside air into the pipe. Easy way to see that effect is just open up a pipe clean-out cover and watch what happens to the draft strength.

That exhaust gas velocity pressure difference inside the pipe can be seen by moving the probe end of a mano gauge from in the middle to the outer wall of the pipe (that's why I don't install mano gauges with a fitting flush to the pipe wall. It gives a lower reading than what the real draft strength is).

On a wood stove, the draft has to be kept higher so there's more pressure difference at any pipe gaps.

If you run a coal stove at very low draft pressures, like some of us can get our antique stoves down to, such as .01-.02 WC, fly ash is just heavy enough to leak out the joints against such low pressure differences, especially when you get a layer of fly ash built up that starts to shield the fly ash near the pipe joints from the lower pressure inside the pipe.

Paul

Install a manometer to monitor your draft pressure and carbon monoxide detectors in the house and stove room. If enough creosote falls to block the flue passage the manometer will drop to zero and the carbon monoxide detectors will alert you if there is a CO danger.

Lightning wrote: ↑

Thu. Oct. 01, 2020 10:25 am

and the carbon monoxide detectors will alert you if there is a CO danger.

The carbon monoxide detectors will alert you if there is a CO danger so best to Train any household pets that may be home alone to leave if alarm goes off...
The real point is CO detector can warn only if someone is home to hear the warning...otherwise first one home gets the warning.

I guess you could get one of those fancy CO detectors that alert yer phone if yer not home then?

H, all that creosote crap is just that--CRAP. A good brushing is tried & true.

Thanks for all the advice everyone!

Richard S. wrote: ↑

Wed. Sep. 30, 2020 6:45 am

The other issue already mentioned is it's going to fall off and it could potentially block the flue pipe if enough falls off at once. Be sure to check the flue pipe frequently.

x2. That happened to me. So much creosote fell down it piled up in the chimney and started blocking off the thimble.