Chimney draft woodburning boiler
I purchased a harman wood burning boiler 3 years ago and love it. However, it eats the wood like jabba the hut. Considered putting in a barametric damper to reclaim and keep more of the heat in the firebox, but afraid it will cool the chimney too much. Is there any other concern I need to consider since I clean the chimney beginning end and middle of the season as far as the creosote buildup. I just feel that the draft is too strong and pulling alot of the heat out of the chimney. Sometimes the chimney even wistles, which indicates to me that there is too much draft. The chimney is 24 feet tall of double insulated stainless, and I’m thinking that the barametric damper would help retain more heat to the water jacket and hence burn less wood. How far off am I on this one? Any ideas?
Mark Russo
Washington pa
Custom Woodworking and Residential Contracting
Replies
Is there a thermostate that opens the combustion air to the fire box or is that open all the time?
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Yes there is a aquastat that opens and closes the damper at the bottom of the firebox electroncally to fluctuate the water temp
when you clean the chimney, do you get a lot of creosote or just a little soot?What is the condition of the wood that you burn? dry or a bit green or damp?
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Talk w/ the manufacturer, first. Is your flue the proper size for your boiler?
Also, if you have either a forced draft or induced draft combustion air fan system, there shouldn't be a lot of free movement of air up the stack when the system is off. If you have either, you shouldn't need a barometric damper as they are for atmospheric burners, I think.
Consider using a thermal energy storage tank to store excess heat from your combustion process. Burn your wood hot and store the heat.
Have you measured your flue temp during operation? The manufacturer should tell you what range that should be, I would think. Maybe there are some adjustments to combustion system that will fine tune that a little.
I assume this is hand fed fuel on an 'as needed' basis?
What clewless said.
As a general rule, a barometric damper is a good idea, even with gas fired - there can be too much draft for them too
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I think you are confused about the purpose of a barometric damper. They are typically installed as a tee fitting on the pipe immediately behind the boiler. The damper does not block off the smokestack, it controls the amount of air that flows from the room into the smokestack. This assures that even tho you have the intake air control dampered down on the boiler, you will still have enough air to carry the smoke up the chimney.
You should be controlling the combustion air through the main air port on the boiler. You have to get that set up properly so that you don't have too much draft. I have never seen a wood boiler that doesn't allow you to adjust that properly. Do you have a draft fan that goes on when the boiler calls for heat?
Barometric dampers also slow the flow of flue gases (and hence the burn) when the draft is too high.
"Ask not what the world needs. Ask what makes you come alive... then go do it. Because what the world needs is people who have come alive."
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That's true. I'm not saying he shouldn't have one..in fact I think every indoor wood boiler should have one...but it may not do what he thinks it will do.
The primary draft control still should be the combustion air inlet, and that has to be set up properly.
It would also help to use unsplit wood in many situations like he has.