Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: shepherd boy on March 14, 2018, 09:58:25 AM
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Anyone using a dryer on an outdoor furnace? Ideas on hooking one up?
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I’ve seen a few “kits” around. Most are just a small HX and mounting brackets. Place it over the air intake for the dryer then run it on air fluff. Generally takes a LOT longer to dry a load of clothes.
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I have done two like that for myself on old dryers, but they didn't last long. I'm thinking the intake puts cold air over the tumbler/fan motor and putting the coil there puts hot air on the motor. And your right took a lot longer to dry. Trying for something better.
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Only thing you could do then is disassemble the dryer and make up a spot in the ducting to place a HX after the motor.
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That's kinda what I have in mind. Need to take the dryer apart and see how it's configured.
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I once heard that a heater core from an 80's Ford escort could be hooked up efficiently. I think I heard it from a guy pushing Natures Comfort stoves............years ago.
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I did one once using a 12x12 2 row heat exchanger that I had laying around. I used I think a Whirlpool dryer that has a metal duct from the heater up to the air intake at the back of the drum. You have to take off the back cover to get to this. On electric models, they put the heating element inside this tube.
I removed the heater and cut open 12" of the duct which is about 6" wide and attached the heat exchanger to it.
It worked fairly well but did take longer to dry the clothes than a normal dryer.
I redid the plumbing in my house a couple years ago to remove some major restriction (10 plate) and was able to go from a PL36 pump to a Grundfos 15-58 (then to an Armstrong 20-20CI)
After I did that, there was not enough back pressure to get any blow to the dryer the way it was connected. I never got around to redoing the piping. I will have to put a pump on it to get the needed flow.
If I do hook it up again, I will probably swap out the heat exchanger with a normal 3 row. I am not sure if I will go with a 12x12 again or use a 6x12.
Another thing I might add is a blower to push air through the heat exchanger. Dryers suck air through them so if you get too much restriction on the air intake and/or if it is an old worn out dryer, it will start pulling in cold air around the seals, bypassing the heat exchanger. My first attempt to do this was with an old dryer with a bad drum seal and it didn't work at all.
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In the winter, I dry my clothes using the heat from my outdoor furnace by simply putting up a clothes line in my basement. I have a fan driven heat exchanger down there to heat the basement and it drys the clothes quickly and easily usually overnight. Also the increased humidity makes the entire house much more comfortable. Since I also use an outdoor clothesline in the summer I have barely used my dryer in the past several years. :)
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Just checked the temps on the dryer intake using electric. Running at 225 degrees. Pretty hard to come close to matching using outdoor furnace. Fluff cycle on this dryer is max 30 min., about what it takes to dry a batch now, so doesn't look too promising.
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Thinking here, if the total airflow through the dryer went up... Maybe it would compensate some for the lower temps. Move the moisture out faster. ?
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Just don't want to destroy this dryer. Just want it as an add on. Maybe I need to get an old dryer that still turns and add a bigger blower and force feed it.
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Some pictures of a blower I made up pushing hot air into the back of a dryer. Took the back panel off and located the wire going to the motor. Created a 120v jumper off that circuit to power a 250cfm fan attached to a 12x12 heatexchanger. Cut a 4" hole in back of dryer next to the air intake. Getting 165 degree air temp from the blower in the tube, more than I expected, but I don't think I'm getting enough air flow, as I think the dryer is pulling additional air and mixing pulling the actual temp in the dryer down. I think I need to change to a 6"duck and get more air in there.
Takes 2 1/2 times as long to dry as electric now.1 1/2 hrs. vs. 30 min.
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You are running the hot air down that silver pipe? It looks like it would be too restrictive.
I would open the dryer and run your fan and see how much air is coming through the intake vent. If it is not as much as you get out the vent without it attached then you the dryer will probably pull air in through other places.
I think you loose a lot more cfm when there is a restriction on the inlet of a squirrel cage blower than the outlet but I could be wrong.
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So basically your (or all) electric dryers boil the water out. Remember latent heat of evaporation will significantly reduce your observed temps after it hits the fabric. I'll go so far as to suggest the air inlet temp of that electric dryer is several hundred degrees. The average dryer generates between 10,000 to 20,000 btu. Seems like a little math could get you the proper cfm requirements at the temperature you have available; which is probably a LOT.
The heating element section on the inlet - that thing looks restrictive, does it turn into a 4" round duct as it enters the drum?
I propose a 6" inlet and outlet would do wonders for the drying time.
I like what you've done there. Personally, 1.5 hours would be fine with me for the few cents it costs to run the fan motors, the woman though, huh, well you know how that goes...
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The 4" silver pipe is the hot air from the coil/blower unit. It just puts air into the dryer, is not attached to the element tube. I agree it is too restrictive, I'll put a 6" there when I get a chance and let you know how that does. 250cfm fan but it is no way you can get 250 cfm in a 4'', so there should be room to play.
The fan on the dryer is on the exhaust, so if you open the door you lose the vacuum on the inlet.
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Did you seal off the original air inlet? If not, I doubt it will work very good. You will need 100% of the air entering the dryer to go through the heat exchanger.
Are you wanting to be able to turn on the electric heat without any changeover?
If not, get an extra heat element tube out of a junk dryer modify. If I remember right, I think it is only one screw to pull the tube.
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You're right. I just had an element burn out. Got a new one on eBay.
I have the old element section of the tube laying in my shop, it held on with two screws. Could cap the bottom and cut a hole in the side to send the air in. Total airflow should go up then and heat better then just sending it in behind the cover near the tube..
Hmm... I'm tempted to try.
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I am sure if you hooked it to flow direct into the dryer it would work better but I wanted to keep the electric option.
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OK, got a 6" duck to dryer, everything else the same. Air temp is 163 going in dryer. Dried a small load, two pairs jeans and two work shirts and socks, 40 min. I think I can stand this. The whole dryer heats up now, so I know I'm giving it all the air it can utilize without going to direct feed. My electric can work as always.
Looks like I'll be burning all summer for sure.
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That's pretty cool.. I like it.
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Will bring this back up, Found out with this hookup, works best if I run the dryer as normal. The outside furnace will bring air temp up to about 165 and then electric will come on some to run at max temp and dry quick on less than half the normal electric use.
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Will bring this back up, Found out with this hookup, works best if I run the dryer as normal. The outside furnace will bring air temp up to about 165 and then electric will come on some to run at max temp and dry quick on less than half the normal electric use.
:thumbup:
Thanks. I'd go for something similar.
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Having a lot of people asking about dryer hookup. Still using mine. Refresh this.