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clothes dryer- hydronic?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by barnartist, Feb 18, 2008.

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  1. Telco

    Telco New Member

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    Perhaps this will help. Regular steel and aluminum are unlikely to corrode together. Anodized aluminum will also keep any galvanic corrosion (GC) at bay. If you were to just put in an anodized aluminum fitting between the steel and aluminum, this would isolate the two materials preventing any GC. Grounding the aluminum radiator will also help. Anodizing is recommended for automobiles that use aluminum fueling parts and ethanol, since ethanol eats aluminum like kids eat Cheetos.

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  2. Gooserider

    Gooserider Mod Emeritus

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    No experience with hydronic stuff, but in the wonderful world of liquid cooled PC's, there has been a lot of experience that suggests that putting copper and aluminum parts in the same system can lead to rapid failure of the aluminum parts, with subsequent leakage - Very uncool because electronics that are leaked on tend to break and let the magic smoke out. I would be VERY hesitant to use an aluminum core in a steel and copper based system.

    In the automotive world, I suspect that what you will mostly find is that what gets used for HC's and Rads is a function of the engine block - Aluminum engines will have aluminum cores and rads, cast iron engines will use copper / brass cores...

    However either your local junkjard or local auto parts supplier can supply lots of choices in radiators or heater cores that are made from brass / copper. When I last checked, which was a few years ago, the copper heater cores new, were cheap enough that it was comparable cost to purchase new vs purchasing used and getting it boiled out and reconditioned.

    On the electric side of things, I would do some checking against the schematics of your dryer. Gas dryers run on 110v, and my understanding is that many electric dryers actually split the feeds and run everything but the heating elements on 110, not 220. This can impact design choices for obvious reasons. It might also be worth looking at the circuitry on the electric dryers to see if there are low current controls for the element heater that could be tapped into rather than the actual feed to the element - after all if the dryer maker has already put in a relay to control the element, why not divert the signal for that, and avoid the expense of a high power relay.

    Gooserider
  3. barnartist

    barnartist Minister of Fire

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    Man, I didn't expect such a nice turnout for this thread. So in theory, if this would in fact work, would it take a bunch of btu's- aka a ton of extra wood? If my house furnace fan is 110k btu,
    it just seems like it would be way less in a dryer. Maybe 10k? otherwise one would heat the entire house with the dryer for 30 bucks a month.
    Hey Indiana guy, hows the wind been out there? BBBRRRRR!!!from Ohio!
  4. Telco

    Telco New Member

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    Gooserider - If you look at that link I posted, it shows copper way down the list from aluminum, which means the two in contact means copper is having aluminum for dinner. An anodized junction between them should prevent corrosion.

    Barnartist - You could always dump the dryer output into the house in the winter to both recover the heat and add humidity to the air. No loss then. You'd just need a well filtered dump box and ducting to reroute the dryer outlet between the inside and outside of the house.
  5. Nofossil

    Nofossil Moderator Emeritus

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    There's a lot of variation between driers, but somewhere around 15,000 BTU per hour should be more than enough. Hardly a dent if your capacity. The trick is that you want it pretty near 180 degrees to get 165 air temp out of the HX.
  6. wdc1160

    wdc1160 New Member

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    BA
    If I am the indiana guy your referring to then yah, Brrrr is one way to put it. This whole week should be crazy. Do you think this is your electric bill problem BA?

    If it didn't require a ton of BTU's then why would we even bother with it. I will dry 3 loads a week tops. I have no reason to bother installing and plumbing with it.
    I do know that @ maybe 2 dollars a day for a family it may justify the expense.

    I have three wooden racks that I can hang up the clothes on. Its slower, but greener.
  7. barnartist

    barnartist Minister of Fire

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    Yup Indy, your the guy. Can never remember ABG362564534376 9er.
    I just looked at the dryer as another thing that uses heat.
    I like the sound of 15k. Your right though about keeping the water at 180. Allot of you guys probably yo yo your temp.
    It might be nice to find a free old dryer that still has a drum that turns to play with. It might look like the worlds first computer at the outset, but who cares in my basement.
    Im sure i'll see a few nice springlike days soon and put the idea on the shelf just like last year im afraid. Maybe if I am patient one of you smart guys will fine tune it and save me some agrivation and some WAF. If she was Marissa Miller (Sports Illustrated), she can use my current dryer all she wants.
  8. Willman

    Willman Minister of Fire

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    Go to a second or third tier salvage yard. Find an old truck. They have the old school heater core and blower motor in a sheet metal enclosure. Mounted on the firewall, not a lot of under dash work.Brass core so no dissimilar metal issues. Easy to hook up quick. All engines have different materials throughout. Aluminum,copper,brass, cast iron, steel,plastic. The automatic tranny cooler is usually brass in an aluminum radiator. Probably the coolant has something to do with the dissimilar material issue. Unless you are running the dex cool in certain gm engines. Besides antifreeze should be changed according to maintenance schedule. Copper and iron have got along fine in all kinds of hydronic systems. I think once the oxygen is burnt out of the water it is ok. HR has mentioned a water treatment product he uses for all his installs.
  9. wdc1160

    wdc1160 New Member

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    BA was the dryer responsible for the electric bill issue u were having?
  10. rsnider

    rsnider New Member

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  11. barnartist

    barnartist Minister of Fire

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    Im not really sure if the dryer is the culprit AB. It does have a faulty countdown timer and the so called auto dampness shutoff switch doesnt shut it off.
  12. Gooserider

    Gooserider Mod Emeritus

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    As I said my experience / learning mostly came from the PC water-cooling side... The common experience there was that mixing Cu and Al in the same system was tending to ask for trouble. Anodizing helped, but was very failure prone, as it is very hard to do PERFECT anodizing, and then keep from damaging the coating when assembling parts - and even the tiniest nick in the anodizing could turn into a crater in short order - there were many threads with pictures of failed components on Silent PC Review. Adding anti-corrosives (such as the stuff in automotive anti-freeze) would help, but only for a while, as those chemicals eventually get used up and the protection goes away. However the all Al or all Cu systems would hold up for extended periods with little trouble. One of the scarier classes of components were actually some of the commercial coolers that would combine a copper contact face with an aluminum body - they worked OK when used EXACTLY per directions, with the specified coolant chemistry, and w/ lots of regular upkeep (coolant changes every few months, etc) for at least a typical overclocker system's life expectancy (maybe a year or two) but any variation from the specified drill could lead to catastrophic failures in a matter of weeks. I never ended up finishing my system (I've got most all the cooling system parts I'd need for it) but I decided very early on that I would not do a combined metals system, and joined many of the other folks on SPCR in trying to talk folks out of doing them.

    As to hooking up the drier to vent indoors - Been there, done that, not a good idea... It obviously should never be done with a gas dryer due to the CO hazard. With an electric dryer it will work, but it causes WAY excessive increases in the humidity of the house - think having the entire house feeling like the bathroom after a marathon shower... We had so much excess humidity that all the windows were getting condensation on them, and the wallpaper near the dryer was starting to peel. I don't know just how much water is in a load of clothes, but I suspect that a large load of stuff with high cotton content (say jeans and towels) might hold a gallon or more, ALL of which gets dumped into the house, way more than a reasonable quantity. In addition, even the best filter won't stop all the lint dust, and that stuff is not healthy to be breathing.

    I have seen heat exchanger type units that are sort of an equivalent to the "Magic Heat" units on stoves, they claim to re-capture some of the heat from the dryer exhaust, without getting the lint and moisture, but I have never tried one. I suspect that it might have the same sort of issues with lint buildup that a stove unit had with creosote buildup - putting blocks on the drier exhaust is a BAD idea...

    Gooserider
  13. guy01

    guy01 Member

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    I may be wrong but I think if you get an old enough radiator or heater core you might have lead isues as well
    Guy
  14. wdc1160

    wdc1160 New Member

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    What does lead do to boiler equip???
  15. steam man

    steam man Minister of Fire

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    I figure there's a lot of lead based solder out there in copper pipe joints. Shouldn't be too much of a problem. Ironically, copper is a big problem in high pressure steam boilers. It can leach out of heat exchangers and plate the internals.
  16. Gooserider

    Gooserider Mod Emeritus

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    My understanding is that lead isn't a big problem in heating systems. It gets a layer of oxide over it, which as long as it remains undisturbed is pretty stable and doesn't do much. In addition, the amount of surface area that is actually exposed is pretty nominal.

    As long as you aren't running potable (drinking) water through your hydronic heating system, there are also not going to be any health related issues, as you won't be drinking that water. My understanding of codes is that technically lead solder is only prohibited on drinking water systems - however most plumbers don't carry it any longer to avoid the hassles of keeping two different materials inventoried, and to avoid the risks of accidentally using lead on drinking water pipes.

    AFAIK, Lead is still legal, albeit seldom used, on heating systems and sewer plumbing.

    Gooserider
  17. drizler

    drizler Minister of Fire

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    I like the KISS principal. About 12 years ago I ran some army 550 cord that I had laying around from some National Guard Outing I had been on. I strung it lengthwise across the basement and have been using it for a clothes line ever since. My bag is to toss the towels ( all the way too many of em the wimmen tend to use) over the line for a day may be two. Then they get tossed into the porpane dryer and it doesn't take long at all. Smaller stuff only gets hung if I feel like it. Those darned towels are what take forever to dry. Hows that for low tec??
  18. Willman

    Willman Minister of Fire

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    Gooserider, I have enjoyed reading your post on task analysis. Key task, secondary task etc. Then another poster inquired as to the WAF factor. Being married as long as I have I immediately recognized the acronym. It got me thinking (oh no). I usually conduct task analysis without knowing exactly the whys or wherefores of how I arrive at the end result (usually positive). One thing I do know without a doubt. WAF. Except the A has different meanings depending on timing and circumstances. First step in selling any project to my CFO is to gain "Acceptance" and then comes the "Approval". I haven't made that presentation yet in regards to my future boiler project. Is there a smiley that represents "shakin in his boots?)
    On past projects that have gained the acceptance factor that have turned out well the the "Admiration" factor kicks in. Sometimes this is a fairly lengthy period. :) I said sometimes. Usually when the Mrs. is the sole reason for the project. Finally comes the "Appreciation" part. Like the sighting of a red crested double breasted ultra rare songbird this factor is the toughest to attain. Many roadblocks exist in attainment of this goal. But it is a worthy goal.
    All this being stated I read plenty on this forum every night to be able to better my chances at attaining all the "A's" Thanks to all who post. It is all worthy reading no matter how high over my head it is. Back to reading.
    Will
  19. BrownianHeatingTech

    BrownianHeatingTech Minister of Fire

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    We also avoid it on heating systems in many cases simply because it isn't as mechanically strong of a joint.

    Joe
  20. guy01

    guy01 Member

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    I was just thinking codes being as strict as they are these days lead would be a headache, and if not now later for sure
  21. Gooserider

    Gooserider Mod Emeritus

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    Not saying you SHOULD use lead, merely that AFAIK, there is no code-related reason *NOT* to use it in a heating system, nor have I heard of any particular effort to get that use restricted further as there is no real reason to do so from a health or safety standpoint.

    Of course, as Joe and others have pointed out, there are non-code reasons not to use lead, and I'm not arguing with those either. I think the only reason the topic is even relevant is that some of the discussion has involved using an automotive radiator or heater core as a heat exchanger - some of those are, or at least used to be, made with lead solder but I'm just saying that is not a stopper if the item is otherwise OK. I would say more of an issue is that some folks run a pressurized system, and my recollection is automotive stuff is only tested at about 20-25 PSI, and isn't really intended to be used at more than about 10-12 PSI. Don't most hydronic setups run about 30 PSI if they are pressured?

    Gooserider
  22. Redox

    Redox Minister of Fire

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    Maybe I should just let this thread die, but I might have some interesting thoughts for y'all. I used to fix appliances in a past life.

    The typical electric clothes dryer has about a 5 KW element giving you about 17K BTU of heat. The typical gas dryer has about 20-25K BTU burner and is 100% efficient because the clothes are the heat exchanger. The dryer controls the heater based on the discharge temperature and is set at about 160F on high heat. I have only found one manufacturer (GE) that gave a CFM figure of 175 CFM through a 4" outlet and is probably typical. This makes for a high velocity in the outlet because you don't want to let the lint drop out of the airstream. You also don't want to try to extract heat from this airstream because it is already saturated with moisture and will condense very easily. Water in the vent will attract lint and collect to form a fire hazard.
    Dryers have only one motor that spins the drum and runs the fan. All dryers are really 120V appliances that tack on the electric element for 240V leading to the problem of 3 wire vs. 4 wire hookups. The 3 wire setup is actually using the ground as a neutral for the 120V and is against code in many jurisdictions. If the dryer loses its ground outside the dryer, the frame becomes charged by the motor and controls. This has been known to cause fires if you are using the flexible plastic duct that has a spiral wire in it. The wire can complete a circuit to ground and become a heating element. Picture a flammable plastic duct filled with lint wrapped with a heating element tacked up to your floor joists. Not good. Most manufacturers will warn against the plastic duct anyway because they aren't very smooth inside and collect lint. This also holds for any kind of heat extraction device.
    Most dryers use a centrifugal switch on the motor to turn on the heater/burner as this is a failsafe in case the motor shuts down for any reason. You can see this if you put an ammeter on the dryer when it is running. The heat will stay on for 1-2 seconds when you open the door and the motor slows down. I don't know about the rest of the manufacturers, but Whirlpool/Sears stopped using multiple heating elements many years ago and only use a one stage heater controlled to a lower temperature. You also migh find that the ignitor in a gas dryer uses 100-200 watts while the burner is lighting (about 10-20 seconds, but this cycles many times during a run). Not significant unless you are off the grid and scrounging for every watt!

    It would seem to me that if you oversize the external heat exchanger on a hydronic setup, you should be able to get 150F air. Multiple heater cores in series would have way too much static pressure drop on the airside. A large radiator with very slow moving air through it would probably be the way to go IMHO. You don't really want to change the airflow through the machine. If anyone wants to try this, I might suggest using a Whirlpool as the heating element is in a rectangular duct up the back of the machine. Take out the element and make some kind of adapter to connect to your duct off the HW coil. Some dryers (GE still?) use a "Halo" type element around the drum that would be very hard to adapt. You might also consider experimenting on an old used dryer instead of your own. That way, if the WAF goes negative, you can put the old one back! Since dryers outlast washers about 2-1 and many people replace them as a pair, there are plenty of good used dryers out there. I can keep a Whirlpool going forever if the motor is good.

    As someone alluded to earlier, why would anybody go to the trouble as the dryer isn't really a huge deal in most households? Then again, as I get to know this group, the question becomes moot; not that I hadn't thought of it already. Anybody wanna hear my idea for a heat pump dryer?

    BTW, large commercial laundries will typically use steam for the dryers as it is easier to maintain one big burner rather than many smaller ones and the fire hazard is greatly reduced. If you want to hear about dryer fires, ask any fireman; they happen all the time and usually due to lack of maintenance.
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