Emergency heat dump for wood furnace

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Micdrew

Member
Jan 15, 2021
66
Maryland
Hello, im heading into my second season with the VF100, I have it ducted into my LP furnace which is about 20 feet away, here’s the dilemma, connecting the VF to the LP is about 25’ of ducting, if the power ever goes out gravity flow will be limited if at all. So I can either have a manual air damper on the plenum that’s always open “wasting” heat into the unfinished basement or install some sort of damper that opens when the power goes out if that’s even a thing, I’ve been looking around on line and I can’t find anything that fits that description, anyone here have any thoughts?
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,531
NE Ohio
Hello, im heading into my second season with the VF100, I have it ducted into my LP furnace which is about 20 feet away, here’s the dilemma, connecting the VF to the LP is about 25’ of ducting, if the power ever goes out gravity flow will be limited if at all. So I can either have a manual air damper on the plenum that’s always open “wasting” heat into the unfinished basement or install some sort of damper that opens when the power goes out if that’s even a thing, I’ve been looking around on line and I can’t find anything that fits that description, anyone here have any thoughts?
The 2 companies that I know of that made a proper emergency heat dump door for wood or coal fired forced air furnaces are both out of business now.
You could install a "power closed/spring open" damper to dump to the basement...but you'll need to do some wiring, and the last I checked they are spendy for good ones, and you would want a good one, no sense buying junk only to have to work on and/or replace it in a couple years...and depending on the damper design, they don't always seal the best.
Contact @sloeffle , I know he bought an EHD for his furnace but soon after changed plans. I don't know if he still has it though.
Good thinking...and if by some chance that one is spoken for , its possible that there is a second one in Ohio that is looking for work right now too.
 
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Unextinguished

New Member
Aug 2, 2022
18
Vermont, northerly, USA
If your other options come up empty consider looking for a Belimo spring return damper actuator on eBay. You'd need to improvise a linkage &/or cables, mounting, etc. and make sure that the one you pick can handle the lift of whatever you rig as a heat/airflow "escape hatch" but it's kind of meant to fulfill a similar function. They come in 24 and 120v -120v having the advantage that you don't have to find and use a transformer of adequate VA for the Belimo, but 24vac maybe being more common and safer to switch depending on how you wire it in. Belimo NF is a now discontinued model but you may find NOS and they're built like a beast (but not lightweight!)
 

Micdrew

Member
Jan 15, 2021
66
Maryland
Quick update, I contacted my local hvac supplier, they fabricated a motorized damper that’s power close spring open so when the power goes out it will automatically open and will immediately dump the heat into the basement.
 

brenndatomu

Minister of Fire
Aug 21, 2013
7,531
NE Ohio
Quick update, I contacted my local hvac supplier, they fabricated a motorized damper that’s power close spring open so when the power goes out it will automatically open and will immediately dump the heat into the basement.
What did that set you back, if you don't mind me asking?
 
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JRHAWK9

Minister of Fire
Jan 8, 2014
1,918
Wisconsin Dells, WI
Keep in mind this setup will only protect from a power outage and not a mechanical failure.....like a blower or low limit failure.
 
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brenndatomu

Minister of Fire
Aug 21, 2013
7,531
NE Ohio
Keep in mind this setup will only protect from a power outage and not a mechanical failure.....like a blower or low limit failure.
That's a good point...and another one that had not occurred to me prior is you if have a short term power outage, where the power would maybe not be off long enough to overheat anything, but right outta the gate you still loose the gravity heat flow to the house (upstairs) that you would/could have gotten otherwise.
 

Micdrew

Member
Jan 15, 2021
66
Maryland
That's a good point...and another one that had not occurred to me prior is you if have a short term power outage, where the power would maybe not be off long enough to overheat anything, but right outta the gate you still loose the gravity heat flow to the house (upstairs) that you would/could have gotten otherwise.
Well with the 25’ horizontal run of ducting to the main house ductwork I don’t think I was going to get any gravity flow, maybe just a little.