Hot Water Clothes Dryer

[jasonweir]

Before I start I know I should have bought a gas dryer but oh well.

I'm using a outside wood furnace (Central Boiler) to provide all my heat and hot water, I have plenty of wood meaning I have plenty of hot water.  I had an idea of trying to convert my electric clothes dryer to run off of hot water.  

Here is my idea, from what I can tell my electric dryer's fan draws air across a heating element and the across a thermostat (thermister, I think).  This thermostat controls the heating element.  If I created a duct on the rear of the dryer and mounted a vehicle heater core in the duct forcing all air across the heater core.  Then plumb the heater core as a separate zone in my house heating system, turning the zone valve on when the dryer is in use.

In theory the air would be heated by the heater core and hopefully would not need the heating element to be used.

I might have to get a broken dryer from the dump and try it before my wife lets me modify out brand new dryer.

Any ideas?

Thanks,

Jason Weir

New Hampshire

[sh123469]

Hi Jason,

I found on Google that the average electric dryer uses ~3kwh per 45 min. load.

3kw x 3.5 (approx kw to btu) = 10.5kbtu or 10500 btu.

Heater cores vary tremendously in size and flow I am not sure what the temp in an electric air dryer is but probably higher than you will get from the heater core.  Looks like, from the little I can find on the net, a car heater core will go 4000 to 10000 btu per hour.  

Looks like it should work but will require longer drying times.

I have never tried this but don't see why it shouldn't work.

Remember to vibration isolate the core and provide good support and anti-vibe on the connector tubes.  They routinely fail due to vibration on many cars.

Steve

[bob g]

would be very interested in your outcome on the dryer project, i too have some reservation as to whether the heater core would get hot enough, but maybe.

i would go pick up a junk dryer to try it on, they are cheap when they quit

and generally quit because of timer, heater element, etc failure, but often times the

thing still rotates

wrong board??? why?

bob g

[nothing to lose]

Why wrong board, rural living ect,, .. Saving and  producing electric  

Kinda sorta falls in there somewhere I think.

First step in going off grid is cutting usage right

Well, my wood burner is indoors. I Modded a gas dryer to a wood dryer, so I don't see why Hot Water won't work though as pointed out it may take longer than normal to dry.

 Maybe longer than hot air directly from the heat source too, and be sure you don't have leaks at the dryer!!

One thing you can do is probably take the wires off the heating coil and insulate them for saftey so they can't short out, touch anything, or shock anyone. If same as my electric dryers they will run fine just never heat and that's what you want.

 If the dryer has a NO HEAT, FLUFF MODE then use that for drying and you probably don't even need to worry about the element heating anyway. My electrics did not have that mode, but the gas  one does.

 No need to ruin the dryer, just unplug the wires so you can use em again later if you want too.

Only thing you really need to do then is make a duct to sit in back of the dryer. All the electrics I have worked with have a flat duct comming down the back where the heating coils are, that's where all the air enters the dryer. Just make a duct to sit back there against the existing duct, coffee cans work well for this normally. I use the metal Maxwell house cans, not the plastic foldgers cans. Now run about a 4" duct pipe from the can to your heat source. Since your using a radiator with hot water, place it next to the coffee can. I like the metal tape, the foil or chrome type stuff. Very sticky and not effected by heat easily. Tape it all fairly air tight. Pump in hot water, dry clothes.

 I would rather use hot air than water if I could, you might want to place the radiator away from the dryer a bit and run a duct to the dryer, if so wrap it with insulation so it doesn't cool the air running through it.

Me, I have the modded gas dryer sitting next to my wood burner. I had to butcher the inside some because it drew air from two places, from the front bottom for gas burner for hot air and open back section for cooler air and mixed them. So I blocked the burners section off with a coffee can bottom (perfect fit) then cut open the back area a little biger and made a coffee can duct that fits well and holds itself in place. The air intake then is about a 4" duct pipe 6" long or so conected to the coffee can and a foil type dryer hose that runs up to the ceiling and dangles down over the wood burner. With a decent fire clothes dry about as fast as with electric dryer, maybe faster, and with a small warm fire it takes longer but still dry nicely.

Either way we get the advantages of dryer clothes (soft and fluffed) and only have to use the electric motor to tumble them. I like clothes from the dryer better than from the line, so next sumer this modded wood dryer will become an outdoor solar heated dryer. Probably line dry mostly, then warm tumble for a few minutes for the soft and fluff. I hate shift shirts and socks that come off the line sometimes.

I let the dryer vent into the house for now. I just connected a pvc elbow and a straight duct pipe pointing straight up. I put a nylon hose over the pipe as a second lint filter. Now we humidify the dry house air while drying clothes as well. So far alot less static shocks around here already. To move hot air around the house and away from the wood burner I have used a elbow or T pointed at the wood burner. That works like a fan to circulate the air while drying clothes. I took it off when I put the nylon filter on, I will put it back on soon. Trying differnt things.

 With the nylon hose we are not getting any lint in the house I can find, the nylon does have a little build up starting that has gotten past the dryers lint filter, so it's a good Idea to use it.

.

[walsdos]

Hello Jason,

I have a Pacific Western 12"X12"X3row rad which I had fitted into a GE drier and was inadequate with water at 180 Deg F. It is possible there was significant air leakage but this was not apparent. Anyhow I think an auto heater core would be way undersized, bear in mind auto water temps are commonly close to boiling point.

Good luck with your endeavors.

[picmacmillan]

one thing i would like to offer up is that the common thread here is water.....what if you used something else like coolant.....what i am getting at is water has a specific heat capacity of "... "1" if you used something else like radiator coolant or whatever that has a better suited boiling point?..just a kick at the can here boys.......pickster

[elvin1949]

use the heater core out of a school bus.

it 10 times bigger than any auto heater core.

later

elvin

[Volvo farmer]

Here comes the ideas from the appliance repairman. A wet load of laundry contains about 10-12 lbs of water, or about 1.5 gallons of water which must be removed from the clothes. An ordinary dryer thermostat turns the heat off at 150F and on below 135F. At the beginning of the cycle, the heating element (or gas flame) stays on almost continuously. Toward the end, when the clothes are dryer, the heat source begins to cycle on and off. I think you'd need a whopping big water to air heat exchanger to do this as fast as a normal dryer. Maybe a car radiator sized thing, off the top of my head. An electric dryer has a 5000 watt heating element. So if you can convert watts to BTUs and a water/air heat exchanger to BTUs, that would be a good starting point. I would suggest using one of the Whirlpool/Kenmore dryers for an experiment like this (the ones with the pull-out lint scren on the top). All the heat comes in from a duct in the rear of the drum and it would be much easier to convert one of these than the style (GE/Frigidaire) that uses heating elements behind the drum. I know for a fact that an electric dryer will tumble with one leg removed from the 220. I'm pretty sure the timer will advance as well. So if you can't find a gas dryer to experiment with, an electric would work by finding which leg is connected to the motor and connecting it to 120V acrross neutral.

And I do not suggest using a nylon sock to catch the lint that gets by the filter. These things plug up and dramatically restrict airflow in about one load. If you want to vent the thing to the inside, make up a 2 gallon bucket with a 4" hole in the middle of the lid, and a bunch of big holes around it. Then put 2" of water inside the bucket. The lint sticks to the water and doesn't become airborne but there is nothing to get plugged up. There's a kit made by Deflect-O that does the same thing but a bucket is often cheaper. Good, unrestricted airflow is very important when you're trying to remove 10 lbs of water from wet clothes.

Good luck and let us know how it turns out!

[bob g]

good response!!

if the temp range is in the 130 to 150 degree zone, then what he is proposing may just work out well.

i really love this board, if you ask the right question you inevitably end up with some good answers

bob g

[bob g]

you might also consider and airconditioner evaporator from a gm product, they are in the range of 40,000 btu/hr rating, are aluminum and pretty compact, should reject the heat to the dryer fairly well i would think

would need to be a captive system with some sort of water conditioner/antifreeze to keep corrosion at bay, but you should use it anyway even with a heater core.

bob g

[thunderhead]

I thought about this, too, with a small baby and an aversion to throwaway nappies (diapers).  A large fraction of our energy goes on washing and drying nappies. :-(

I would have thought that one car heater would not be sufficient, but the solution would be to put several one after the other.  The first one to get incoming air should be the last one to get incoming water, and so on - that way the air is already preheated when it hits the hottest water.

Let us know how you get on - since hot water can also come from solar heat or load dumps, this sounds very interesting.

[nack]

I think the phase change is what makes evaporators 40k btu instead of 4k.  Heater cores have similar or better fin density, and tube sizes that are appropriate for fluid.  

[Opera House]

Regardless, it will take longer.  The electric element in my dryer burned out and I replaced it with a new one that I had bought at an auction.  After my better half did the first load, she complained that it took too long and that she had to restart the load. This element was half the power of the old one.  The problem wasn't that it took to long, but she had to go back and reset the timer.  To solve this I installed a repet cycle timer in series with the timer motor of the dryer.  The repeat cycle timer turned on for five minutes and then turned off for five minutes.  The cycle continues to repeat.  So if you set the timer for 40 minutes, the dryer runs for 80 minutes. This lets her set and forget!  This is just in case you don't have a dryer that senses moisture to turn off.

[nothing to lose]

"And I do not suggest using a nylon sock to catch the lint that gets by the filter. These things plug up and dramatically restrict airflow in about one load. "

 Well I would advise watching them, but no they don't plug up very fast. The dryers lint filter does plug up in one load or often less. Heavy towels, fannel shirts, blankets ect.. are fast to collect in the dryers filter in less than one load at times. We check the clothes durring the dry cycle and also clean the dryers lint filter then and often have maybe 1/4" built up loosely. The nylon sock on top of the vent pipe has been in place now for at least 12 loads and has some fine buildup in the toes, not alot though, and only a small patch barely thick enough to even see here or there on the leg part.

" Good, unrestricted airflow is very important when you're trying to remove 10 lbs of water from wet clothes."

Yes I agree. And using a clean nylon panty hose type stocking is about as free flowing air as you can get and still filter so fine. What I do is pull the top of the stocking over the pipe and let the rest blow in the breeze. For my pipe and the stocking use it holds itself in place, otherwise a rubber band would hold it. Stocking hangs limped over when not in use and blows upright when dryer is running. About a 4-6" long filter depending how you put it on. Working great!

 Sooner or latter it will need cleaned same as any other filter, so far I haven't needed to.

The buildup now is just enough that the toes no longer stand staight up, enough lint was collected to make just enough wieght to hold them at about half mast. That just menas the air is comming out the sides of the stocking more now and lint will be collecting in that area a bit more than it di to begin with. I would clean it but I am watching to see how it does for awhile. Airflow is not restricted.

Cleaning it is simple, turn inside out, brush off any collected lints, run water inside it or blow with air hose, put it back on.  Or you could just toss it out and use the other leg!

I would not use one on a normal gas or electric dryer maybe as the air coming out would be much hotter. Perhaps that's also why this does not fill the sock? Maybe the lint is still moist in the dryer since we are drying with cooler warm air instead of hot air. Maybe the lint tends to collect more in the dryer moist, instead of being dry and blown past the dryers filter??

I use nylons for alot of filters they work great, when we had a problem with rust type particals in the water and gritty bathtubs I put a nylon over the tub faucet (and others) and strained the grit out of the water. Then I found it was coming out the hot water tank and flushed it extremely well and filled several nylons with rust. Where that came from I don't know, wasn't normal sediment and haven't had problems since, no leaks either.

[nothing to lose]

130 to 150 degree zone

Not alot. Should be easy to get coolant that high, only problem would be drawing the air through slow enough to extract the heat from the radiator. These dryers move a nice volume of air, not sure any measurements of it, but it's a good bit.

In a different type of post a person has the picture of a heater he made. Round duct pipe with copper tubbing coiled inside and a cap on the end inside the coils diameter to force the air through the coils spacing so it does not just blow straight through the pipes in a straight line. Something like that may work well for this.

Connect the duct with tubbing to the back of the dryer (same as you would for other methods) running up to near the ceiling. The dryer draws the warmer air from the ceiling down through the copper coils heating it. For this type use you might want to block the center of the coils at the top and maybe the outer section between coils and duct at the bottom to force air through the coils. Run hot water into the bottom and out the top for the coils so it's prewarmed like metioned for using radiators. Hotest at the dryer. Might be easier and better than using radiators? Longer distance to heat water, several feet of duct instead of 3-4" thick radiator. Less chance of leaks, compact taking up less space. Maybe cheaper and easier to find good scrap tubing than good non-leaking radiators. If buying new probably alot cheaper!

Really the main key to the whole thing is very simple really. Tumble clothes, blow air, that's all that is needed. The warmer the air the less time needed for tumbleing and the less electric used for the motor. But room temp air will still dry the clothes just fine, might take all day though. We often hang shirts on the shower rod to dry, and clothes hanging on the line in the shade don't get to 100F either. In the past durring wither we have hung some things near the wood burner and used a fan to blow air acrossed them, about 90F maybe for the air temps hitting the clothes and they dried pretty fast. So you don't really HAVE to have alot of heat. And don't forget you can always add more coil or radiators if wanted.

And I think we have all dried socks in the oven before

 Well ok, not in the oven maybe, but needing dry socks and having a grid failure I have dried them hanging in front of a 400F oven before. So the temps needed to dry clothes range from room temp to not burning them ( lite and crispy or untill toothpick comes out clean)

The warmer the better to a point for heavy items like towels, jeans, blankets. But don't forget low  heat for the delicates. If your wife shrinks her lacy nighty she might think she's getting fat and ruin the mood and there goes your night!

[nothing to lose]

"Longer distance to heat water"

I meant longer distance to heat the air.

[nothing to lose]

It won't nessacarly take longer, it depends on the tempature of the air. Your smaller coil probably was not getting the air as hot as the one you replaced did. If the dryer was designed to heat air to say 140F and you installed an element that only heated it to 100F then it will take longer of course. But if you piped in 140F air from any other source then it would have dried just as fast. Doesn't matter where the heat comes from, just the tempature.

All the manufactorers try to get the fancy stuff extra cycles etc.. to grab customers away from the compatition, so they may do alot of things different. But it all boils down to basics, bounce clothes, blow hot air. That's all there is to it! Fancy cycles and other doo dahs might be nice but the best electric dryer I ever had was a very old Sears model with one dial. Turn to the number of minutes you want it to run with heat, or other way for minutes to run without heat. That was it. Bounce clothes and either blow unheated air or heated air.

I think some of the fancy ones will blow heated air awhile then unheated air awhile so as to not over heat the clothes. They don't just blow 140F all the time or what ever temp they use. Kinda like the kitchen stoves oven, you set it to 450F and it burns gas awhile, then shuts off, then burns awhile, then shuts off. The average temp might be 450F in the oven but at times it's much higher at the burner and other times theres non coming from the burner. I think some electric dryers do about the same thing, not a constant heat source,( I was watching one do this awhile back, not sure the brand)

 and for sure this gas dryer I modded to a wood burner dryer did that.

[nothing to lose]

Oh ya something I was gonna say about the cycling. If the dryer normally cycles the heat on and off like the one I said above I watched do that, then constant warm air will dry clothes faster at a lower temp than hot/cold cycle with the element heating and cooling.

If the average air temp durring drying is 100f with an electric element sometimes suppling 140F air and sometimes room temp air, then a constant 120F air source will dry clothes faster.

I think a quick test should be in order for people using normal dryers. Put some dry clothes in the dryer and run for 20 minutes or so as if you were going to dry them. As soon as the dryer stops put a wall thermometer into the pile of clothes and see how high it actually reads. That should give a good Idea of the real temps involved.

My wall thermometer goes to 120F, I would try it but I don't have a normall dryer to test.

My theory here is the actaul temps to dry clothes are far less than what the element heats. In other words you have 150F heat at the element maybe but not at the clothes!

Running dry clothes for 20 minutes should give you clothes at the air temps actually used for drying. Trying to measure the exhausted air will not be acurated for many reasons, especailly if the dryers cycles the heater on and off, sometime it should be hotter than other times, plus loses in the duct to lower temps, windage (mixing room air), ect..

One of the reasons I don't really think the air is as hot as thought is the clothes should be the same temp when done or run too long. I have taken clothes out the minute they stopped and put them on in a hurry, YA they were hot, but not like 150F should be!

[Ward]

For many years growing up we had a dryer that run on 110v and used cold water.  

If my dad was still around I would ask him how it worked.  As near as I can remember

The air was drawn out of the dryer drum to a chamber that had a fine mist of cold water

sprayed into it, this would suddenly cool the air and cause the water to come out of the air, the air was then heated some by a small heating element and run back into the  dryer drum.  The problem was the chamber that had the sprayer in it tended to rust out.

[jimovonz]

In my limited experience of clothes dryers, they do little to reclaim the heat from the exhausted hot air. I think you might get much better savings by building a good heat exchanger for the exhaust/intake before you even consider an alternative heat source. I have pondered for a while on converting a dryer to use solar heated air. My project list never seems to get any shorter...

[troy]

And now for something completely different...

If you don't need the tumble action, you could make a home grown version of the euro towel warmers.  Just run copper tubing back and forth a few times (five or six horizontal runs, six inches or so apart) so you can hang your jeans or whatever over the top pipe.  The pipe contains your hot water and everything dries without any noise or any parasitic electrical losses from the motor.  The moisture adds to the humidity of your house (a good thing in the winter...) and there's no wasted heat, it all ends up in the house since there's no exhaust.

Good luck and have fun!

troy

[jimovonz]

Exactly what I have done at my place for towel rails in the bathrooms. I have solar radiant hydronic floor heating, so it was a simple matter to route the PEX pipe to the surface, attach a length of 1" copper pipe bent into the usual 'S' and return it to the floor. Looks great and the towels are always dry and warm!

If you consider doing this, it is a good idea to make all connections above the floor so that any potentially leaky joins are accessable.

[bob g]

phase change or not the core still has to reject or absorb the 40k btu's, the heat has to be moved to the medium one way or another., have you looked at one of these gm cores?

i would lay you odds that they are a lot more efficient and have much larger capacity than a car heater core

the gm units i mentioned have around 5/8 and 1/2 inch tube/ports that can easily be connected to.

they are cheap used, but very expensive compared to heater cores new. and being aluminum and not from a wreck are sure not to leak like a used heater core may.

just a thought

[Volvo farmer]

Well, for your application, I guess a nylon stocking is okay. As a repairman, I've seen a half dozen short ones completely packed full of lint and forgotten behind the dryer. The customer wonders why their clothes don't get dry or why their element is burned out. If you keep an eye on it, use the whole leg of the stocking, and clean it often, I suppose there would be no problems. Problem is, most people don't take responsibility for this type of maintainince and if the repairman advocates a stocking, it becomes his fault when the thing gets plugged up. I too think your low heat situation might be contributing to yor lack of lint in the stocking. I've seen just the toe plugged up in one or two loads on a normal electric dryer and a dozen loads would plug the whole thing from what I've seen.

[nack]

I have not seen any a/c evaporator newer than early 90' and very few newer than early 80's.  It is not usually a major failure point, and I've seen them most often as that damn thing I have to deal with to get to something else under the dash.  Most of the ones I have seen aren't much bigger than the accompanying heater core.  Yes they are invariably made of aluminum.  The heater core that lives in the same box with it is either brass, or aluminum core with plastic tanks (yuck!).  I still think the heater core could reject a lot more heat than it does if it had the kind of temp differential that the evaporator sees with the phase change, and therefore doubt that just using an evaporator will automatically boost the thermal transfer to the 40k btu level.  You make a good point about the probable usability of junk yard parts (heater cores tend to show galvanic erosion after years in a car), I have never recommended a used heater core to anyone because the repitition of labor when if fails prematurely can't be justified by the price difference between new and used heater cores.

[bob g]

nack:

i hope i wasn't suggesting that the evaporator would do the job with water

at the 40k btu range,

basically i was just trying to illustrate them as a possibility

i too would never recommend a used heater core, as i hate replacing them as much

as you do.

bob g

[nothing to lose]

I'll probably clean it out tonight, we did alot of heavy stuff last few days. Was cold and had a good hot fire going for awhile. Did lots of drying

I think the lower the heat the moister the lint and the easier it is traped by the dryers filter so less escapes to be caught by the nylon. I know I said that before, but now I had a really HOT fire going, actually hotter than I wanted (different woods) and the dryer finished the clothes pretty quick. I think the air was actually alittle hotter than using gas or electric this time. I did get more lint than normall also into the nylon. Normally I won't have such hot air. I actually sprayed a little water onto the fire to slow it down some for awhile. Dry oak was VERY dry, and had lots of bug holes too making for very fast hot burn lasting a long time!

Yes anytime a filter clogs up it makes a device work harder. I try to keep most of my filters where I can see them easy and also change or clean them easy. A hidden filter is just a problem waiting to happen do to neglect.

[nothing to lose]

The heat exchanger is a good idea if running it normally or if you don't want the heat in the room. But you have all the moisture to contend with, water when you cool the air enough with a heat exchanger.

If taking room air and venting back into the room, a heat exchanger wouldn't be worthwhile since your not losing any heat. If your blowing the exhaust outside, then maybe it's worth something, but then it depends how hot the air is leaving the dryer.

[nothing to lose]

 I like that idea and will build myself one

We don't heat the bathroom much, open the door and let the warm house air in before taking a bath, and we don't sit there reading alot either. It's warm enough the pipes don't freeze (or other stuff) and we won't get stuck to anything due to frost

Otherwise the bathroom here is the coldest room in the house, just what gets through the uninsulated inside walls or around the door.

That idea of a towel warmer piping would make a nice towel rack, polished copper, and add to the warmth of the room too. Also I need to work under the bathtub, when I was working on the shower I had to take off a panel. I found holes for about 1" pipe to fit through the floor for some reason. Gotto fix that, no wonder it's cold in there. Anyway, might be nice to have a warm bathtub too. Run the tubbing under the tub to warm it and that will warm the room also.

As a clothes dryer though I think it would take along time to dry them won't it. Good Idea if you have the space and time, just seems like without much moving air even being warm the clothes will take most the night. Heavy stuff like jeans and towels?

[jimovonz]

Of course you are correct - I forget sometimes that not everyone lives in such a temperate climate as myself! Dryers in NZ almost exclusively vent to the outside and thus waste the heat in the exhaust. As you mention, there is significant moisture in the exhaust (obviously all the moisture in the clothes that are being dried goes somewhere). If you were to utilise the exhaust heat inside the home, would you not have to deal with this moisture anyway? Surely you wouldn't just vent the moisture into your home? Even if you can utilise the waste heat in the exhaust to heat your home, if your dryer is electric you still may have more efficient/cheaper means for heating and thus it would still make sense to increase the efficiency of the dryier. Especially if you are producing the electricity yourself. Even with a heat exchanger (which is never 100% efficient), you could still vent the now (mostly) dry exhaust into your home to reclaim the last bit of heat. I don't think that dealing with condensate would be a biggie, rather keeping the heat exchanger effective by removing all the lint might be the biggest obstical.

[weldingrodd]

I am sure your idea will work

I saw a heat exchanger that mounted in a hot air furnace to heat a whole house and it was not a lot bigger than a car heater core.Am sure a heater core would do the trick. If you had to leave clothes in an extra 15 minutes ..so watt!!

PS: NAPA has a large selection of core sizes available .But probably cheaper at Auto Zone or Advance Auto.Prices started around $30 and go up from there .

Thinking back on last time I change heating element in my dryer.....Should be no problem at all to mount a core inside dryer. You just may have a saleable idea here...LOL

[jimjjnn]

The water dryer was a condensing unit. It passed the air through a set of coils that had cold water running through them and the hat hair being able to hold more moisture than cold would be condensed out on the cold coils and thence into a drain. Similar to dehumidifiers now being used in homes now. The high priced dryers had a refrigerator system that cooled the air down condensing the water.

I saw some of these units as a kid, but had completely forgotten about it.

[jimjjnn]

BTW, the condensing units didn't have a vent on them Just a large lint filter and a water drain