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Author Topic: Draft or pressure?  (Read 1471 times)

patvetzal

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Draft or pressure?
« on: December 11, 2016, 12:29:12 PM »
Had years of experience with airtight (and not so airtight) stoves and fireplaces but now we have a OWB with a small fan and gravity damper. It heats two houses (and DHW) and when it gets much below freezing  runs fairly constant.
When the fan runs and it is calling for heat we get a "nice" steam/smoke plume but we also get irregular puffs of smoke out the adjustable vent hole in the door, indicating a varying firebox pressure. When the fan shuts down the door hole sucks fresh air in and keeps the fire going, like the vent/damper on an airtight stove.
Is it normal for smoke to puff out this hole or does it indicate a restricted chimney?  The hole  is only about 1/2" diameter.
Right now we are burning blocks of frozen hardwood that got left outside and are pretty icy when they go into the firebox :pic:
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80 acres of Bancroft bush and Ontario rock, a sweet wife, a few chickens, fishing rod, most everything I need....Most of it made by John Deere, Polaris, Stihl, Ruger, Jeep or me...

patvetzal

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Re: Draft or pressure?
« Reply #1 on: December 15, 2016, 09:24:25 AM »
The next day I found that the fire was almost out at noon, water temp down to 87F (and level pretty low) with the firebox full of half burnt birthday/Christmas paper. Tenant came home at 4pm to a cool house. He was convinced that we suddenly needed to add height to the chimney to get a decent fire, not to mention tracking down the water leak.
After a quick chimney clean and some dry clean wood the water shot back up to 170...
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80 acres of Bancroft bush and Ontario rock, a sweet wife, a few chickens, fishing rod, most everything I need....Most of it made by John Deere, Polaris, Stihl, Ruger, Jeep or me...

agriffinjd

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Re: Draft or pressure?
« Reply #2 on: December 15, 2016, 04:57:17 PM »
Check your pipe fittings from the stove to the underground lines and from the underground lines to your pex in the houses.  I've noticed sometimes with a big heat change they need to be tightened.  So if you're fire went out and your water temp dropped 100 degrees in a few hours, it may have caused the fittings to loosen from the contraction from the temp drops and you lost some water there. 

Also, if you are dropping that fast on temp it's probably from the forced air blowing into the firebox from the small fan.  It's shooting in cold air and cooling the water.  Do a search on this site for slimjim's posts about how to wire in a shutoff switch that will kill the small fan when the water temp drops below a certain set point.  That should keep you from losing heat so fast if the fire goes out.
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