Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: Freekazoidd on April 14, 2014, 07:38:54 AM
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How big of a heat exchanger would I need for a well insulated 24x24 pole barn? I have 6" of insulation the walls and 9" in the ceiling with ridge vent. I currently and heating with an P&M ML30, which for the last couple years is awesome. It heats my 1500 sq ft house and my 30x40 workshop. I smile when I think of how much money I save not buying fuel oil to heat just my house.. :thumbup:.....especially this last winter...it was a cold one here in Michigan. Went through a lot of wood. Anyway, is there some sort of figuring or method to figure this out? Thanks for any help!
Brian
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Not sure on size for sure I would think it really wouldnt hurt to go to big, its not like a condensing furnace where they need to be sized correctly to be efficient. I'm shooting from the hip here but I think 100k btu.
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Check this website, dragon's breath was the one I was thinking on getting for my garage.
http://www.altheatsupply.com/ (http://www.altheatsupply.com/)
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I agree with jWood, but I would call your local or not-so-local supply house and ask then to size a heat exchanger; they should be able to get you the right size based on expected heating load, pipe sizes and weather its water to water or water to air.
If they spec a FPHE, with less than say 20 plates (personal limit) consider upsizing cause it will cause a lot of head pressure; upsizing generally gets you larger inlet ports and smaller head loses.
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if you go too big with a water to air exchanger you will be sending back return water likely too low of a temp and you will have to slow down your fan or block off part of your rad as to keep return temps high enough not to cause your thermo valve (if you have one) to slow your water delivery
i would think it would be a good idea to first know how many gpm you can send to your exchanger and then size the exchanger for that
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If you figure out what size you need let me know I have 12 of them of different sizes, maybe able to hook you up.
Informer
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Freekazoid,
You have 24 x24 + 576 sq. ft. x 55 btu per sq. ft. rule of thumb, = 31680 btu needed. Now if the walls are over 8' you would have to adjust for that. If they are 16 ft. you would double the btu's needed.
A 12 x12 Heat exchanger is 60,000 btu's at 180 degree boiler water temp.
A dragon breath heater is 70,000 btu's at 180. It comes with the fan built on it, where the exchanger has no fan. You would have to mount it on a fan of some sort.
Greg Steinacher
618-401-0726
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And dragons breaths are made in USA at least the that's what they say!
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Hey thanks for all the great responses. I should have told you guys that I will be heating the shop all the time so my equipment does not get hot-cold start-ups. Because I was in a sort of panic, I ended up using a 100kbtu heat exchanger, which may be overkill, but the last time I went in my shop I had crazy moisture all over my wood working tools which caused rust. :bash:...just over a span of a couple of days without going in there. The 100k BTU exchanger works great. It is actually more than adequate to heat less than 600sqft of well insulated space. I ended up putting a simple box fan and leaving it on low at an angle blowing towards the ceiling to keep the temp at a very comfortable 62 degrees. Now I can clean up my stuff with steel wool to clean the rust. Thanks for all the help everyone. It is appreciated.
Brian
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Glad its working for you! I'm going to go with the 100,000btu Dragon Breath unit heater, I could build my own with a squirrel cage but with 800 sq ft I don't need to move as much air as a squirrel cage pushes around.