# clothes dryer- hydronic?



## barnartist (Feb 18, 2008)

Last season I fiddled around with the notion of building a heat exchanger and rigging it to our clothes dryer. But Im not tech enough to know just how to trick the dryer into running the cycle without its juice drawing, meter running, wallet draining on board heater. I made a long curling copper coil thingy that would fit inside an 8" pipe. It would probably need some fins on it to extract more heat from it though. Anyone know how many btu's or air temp it would need? Does any company make something like this already? My dryer has plenty of empty space inside for "alterations". 
Lets hear some ideas fellas.


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## Nofossil (Feb 18, 2008)

Interesting idea. Need to have an idea of the air temperature that dryers use / need.

My sense is that you'd have to use something like an automotive heater core or radiator to get enough surface area.

They use a simple snap-action sensor for overtemp protection - not sure if there's anything to detect undertemp. Maybe they figure that you'd be able to tell if the heating element wasn't working....


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## mtfallsmikey (Feb 18, 2008)

easy to find a dryer's operating temp...use an IR thermometer, stop the dryer while running, shoot a temp...might do that this evening myself!...While the discussion of car heater cores/radiators is still fresh, has anyone used one to construct a space/wall heater box?


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## deerhuntrer (Feb 18, 2008)

IM suprised that manufacturers have not come up with this yet. My wife, who an engineer, also wanted to do something like this but has ZERO time to plan this out and design it given her current job. Dryers suck electricty and we use ours alot. She wanted to make a heat exchanger from our OWB. Its an interesting idea and I think it could work but Im zero help as engineering baffles my wee little brain. Id rather make beer.


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## hkobus (Feb 18, 2008)

Hve been thinking about the same thing Barnartist, I was looking at using a small utility heater for in farm tractors. TCS has them in different sizes, with and without fan build in. Just not sure what the Btu req. would be. Build this in an air intake and run "airfluff"


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## barnartist (Feb 18, 2008)

Im thinking it will take a bunch more wood to run one if its completed. Im thinking maybe for summer use along with my DHW, that way maybe I could still charge a storage tank every few days... It would be easier to cloths line them I know, but wife doesn't like air dried jeans much. She doesn't like the line much either.
What about a long narrow exchange, much like a side arm does, except thinner material? If I need a big heater core, then Im not sure how to get air to pass through all of the core evenly, outside of building a furnace style ductwork.


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## barnartist (Feb 18, 2008)

Good idea Hog, that then makes me think about a kickspace heater. Maybe a kickspace on roids would get it done.


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## sled_mack (Feb 18, 2008)

I've thought about this, too.  But in a different way.

My drier seems to suck air in from the bottom.  My thought was to sit the drier on a pedistal, which would really be a plenum.  Seal it to the bottom of the drier.  Now, laying it horizontal, you could put something like a full car radiator in there.

Even if it did not get hot enough to completely dry, it should reduce the electric heat required.  If it wants to see 150 deg air, and you take room air at 70 deg, bring it up to 130 deg, now the drier only has to raise it the remaining 20 deg.  Assuming the motor to spin the drier and run the fan take much less electricity than the heater, you could probably disable the heating elements and just let the drier run longer.  How much longer would depend on how hot the drier normally makes the air compared to how hot your heat exchanger could make the air.


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## steam man (Feb 18, 2008)

Any hot air duct better be hooked directly to the dryer air intake, whatever that may be. I don't know many electrical/plastic components that like those temperatures. Kind of reminds me of Chernobyl. I had a refrigerator that caught on fire (electrical). Makes a hell of a mess. You should also consider how the UL rating of the dryer will be void. What would your insurance carrier think? I hate to be a party pooper but it would make a great youtube video. Years ago we converted to a propane dryer and cook top. Saved quite a bit on Maine's high electrical rates.

Not saying it can't be done.........nothing time and money can't solve.


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## Eric Johnson (Feb 18, 2008)

Seems to me if you use something like a toe-kick water-to-air hx that you'd never see temps in excess of 180 or 190. Is that enough heat to run a dryer? I don't see any fire danger with a setup like that. Our dryer is the only gas appliance we use in the winter, since the boiler is shut down. I'd like to find a way to take our gas consumption down to zero.


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## barnartist (Feb 18, 2008)

surely 120-150 air would get it done. I get 90-100 out of my air ducts from my furnace. 
Be nice to make a friendly on off switch for the dryer's on board heater for when your boiler is down. All this sounds fairly simple. How much for a kick space heater ballpark?


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## steam man (Feb 18, 2008)

I'm am thinking that if you expose the whole dryer or even components to heat it wasn't meant for it could degrade them, especially electrical and plastic stuff. Hard to say what would happen. I suppose you could duct a heated air vent directly to the drum with some measure of control and safety shutdown like a motorized vent damper. Conversion of a gas dryer would seem to be easier.


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## Sting (Feb 18, 2008)

Last season after installing my biomass boiler and making my DHW successfully I looked for the next goal - laundry- I posed this question to my buddy who is a life cycle tech for a large washer/dryer manufacturer. They produce industrial laundry dryers that use steam, gas and resistance heat exchangers. After consulting several design engineers that think about laundry appliance operation all day - he responded that I would be better served to hang the laundry in the basement circulating house air with a box fan. 180 degree hot water will not produce enough hot DRY air in an enclosed appliance regardless of the HX size  -  and the extended appliance cycle time will similar or only slightly better to setting the dryer on air only for the load of damp laundry.


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## barnartist (Feb 18, 2008)

If that air is so damp, then would we not have moisture problems in our house? Not sure I buy it, but could be wrong.


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## Nofossil (Feb 18, 2008)

We need data. Without knowing the air temp that driers use, we can go in circles all day.

Dry is not an issue. Makes no difference if you heat the air with an electric element or a hydronic HX - it's the same air. As long as you can get it hot enough, it's all good.

The amount of energy required is in a reasonable range - 10,000 to 15,000 BTU/hr.

Preheating the air might not be the answer. I suspect that driers merely add a fixed amount of heat to the air they draw from the room. If you preheat, you might just be increasing the air temp that goes into the drum - not a good idea. An extra 100 degrees could be bad.

If the temps work out, my inclination would be to build an enclosure around a radiator or heater core and duct that to the drier's intake. I'd replace the heating coil with a 220vac relay, and run the relay contacts to 24VAC and a zone valve, so that when the dryer wants heat it will open the zone valve.

The futziest bit would be the intake ducting.


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## Sting (Feb 18, 2008)

nofossil said:
			
		

> We need data. Without knowing the air temp that driers use, we can go in circles all day.
> 
> Dry is not an issue. Makes no difference if you heat the air with an electric element or a hydronic HX - it's the same air. As long as you can get it hot enough, it's all good.
> 
> ...



let me contact my dryer engineer buddy - should have an answer later today


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## Sting (Feb 18, 2008)

This was faster than I expected - he must have been online!

...............................

At first it sounds like a waste of time! Unless you have nothing but time on your hands to run a hot water heat loop and radiation!

Our gas dryer fires @ 22,000 BTU/Hr. I figured out the Current pricing on my gas fireplace if left on over night would cost me about $0.13 cents a night. and that's firing at about 25K Btu. Our dryer typically cycles off @ 260F.  both Gas and Electric  Again this temperature would be the Maximum, or worse case  FIRE!

Electric Heat is more energy efficient because its resistive heat.  Gas is only about 80% efficient.

We build Steam heat units however in testing they take longer to dry.  60 psi steam is super heated to about 325F.  again you are transferring the heat thru a coil and heating the air as in your car heater core, not very efficient!  Again this is STEAM and Not Hot water.

I still like to hang things in the basement like sweatshirts and nice stuff, and usually the same day with just a oscillating fan blowing on the cool 65F basement air my stuff is dried quiet nicely.

I would base my dryer decision on the price of LP, Natural and Electric.   Leave us to build your quality appliances!

Name and address withheld.


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## barnartist (Feb 18, 2008)

Im certain steam would pet out more moisture than unboiled hot water. My dryer costs way more than 0.13. 
But thanks for the BTU rating.


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## steam man (Feb 18, 2008)

I know anybody heating in Maine with resistive heating has outrageous electric bills. The following is pretty much what I learned in college decades ago:

From the Dept of Energy:

Electric Resistance Heating
Electric resistance heating converts nearly 100% of the energy in the electricity to heat. However, most electricity is produced from oil, gas, or coal generators that convert only about 30% of the fuel's energy into electricity. Because of electricity generation and transmission losses, electric heat is often more expensive than heat produced in the home or business using combustion appliances, such as natural gas, propane, and oil furnaces. 

If electricity is the only choice, heat pumps are preferable in most climates, as they easily cut electricity use by 50% when compared with electric resistance heating. The exception is in dry climates with either hot or mixed (hot and cold) temperatures (these climates are found in the non-coastal part of California; the southern tip of Nevada; the southwest corner of Utah; southern and western Arizona; southern and eastern New Mexico; the southeast corner of Colorado; and western Texas). For these dry climates, there are so few heating days that the high cost of heating is not economically significant.


Looks like the clothesline is the cheapest way to go. If I could only get the wife to use it.


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## Sting (Feb 18, 2008)

barnartist said:
			
		

> Im certain steam would pet out more moisture than unboiled hot water. My dryer costs way more than 0.13.
> But thanks for the BTU rating.



An exchanger powered by steam - hot water - Resistance - gas is simply an exchanger - there is no moisture to "give off"

but there is various potential of BTU 

Is that not a correct analogy? Just trying to remain positive here!


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## BrownianHeatingTech (Feb 18, 2008)

Sting said:
			
		

> barnartist said:
> 
> 
> 
> ...



The hotter the air, the more rapidly it will evaporate water.

If you are using conventional hot water, you are limited in terms of how hot you can get the air (since it will be cooler than the hot water), whereas the superheated steam was being run at over 300 degrees.

Cooler (relatively speaking) air will require more airflow to achieve the same amount of drying.

Whether the increased electrical usage for running a faster fan for a longer time will compare to the electrical usage of a resistance element is something that would need to be analyzed, probably experimentally, since there are a lot of "quality of drying" issues which would be hard to model computationally.

Someone needs to get a decent dryer (one with an efficient drum motor, since some may have very inefficient motors turning the drum, accounting for a lot of the energy usage), and measure the air flow.  Then install a wot water coil in place of the electric element, and attach a variable-speed fan and measure static pressure with the hot water coil in place and set it for airflow to produce similar btu's to the original heater.

Then experiment with similarly-wet loads of clothing (I'd suggest using a certain set of towels, since they are very uniform) and use a killowatt-hour meter to find actual energy usage for a few different combinations of fan speed and drying time, to plot a rough curve and see if the most-efficient combination can be found.

Joe


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## Turner-n-Burner (Feb 18, 2008)

I wanna know where in the world I should live so I can run a 25K bTU fireplace all night for $0.13.  I mean, then my 100K BTU furnace would only cost me $.60 a night.  Factoring in days too, I could heat my whole house for about $30 a month?  yeah, right.

methinks your buddy was a little liberal with his decimal places - or unit conversions, or afterwork cocktails...  

I think the question needs to be - how many cycles a week does your dryer run?  And what is the cost of that cycle.  I think you'll be surprised at how low that number is.

Your time and energy could be better spent removing the water mechanically.  i.e. run the spin cycle on your washer a second time, or upgrade the motor and pulleys so it'll spin faster  !


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## BrownianHeatingTech (Feb 18, 2008)

Turner-n-Burner said:
			
		

> I wanna know where in the world I should live so I can run a 25K bTU fireplace all night for $0.13.  I mean, then my 100K BTU furnace would only cost me $.60 a night.  Factoring in days too, I could heat my whole house for about $30 a month?  yeah, right.
> 
> methinks your buddy was a little liberal with his decimal places - or unit conversions, or afterwork cocktails...



Yeah, even if it only runs half the time, and we call the night 8 hours, that's still #0.13 per therm, which would be extremely inexpensive gas!

Joe


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## wdc1160 (Feb 18, 2008)

I love the idea B.A.

I did a little testing, because I knew that I had to have the biggest piece of garbage 2nd hand dryer of us all.

DISCLAIMER I am not responsible for a decline in WAF if you take this as optimum performance numbers.

My dryer lived in a barn for about 3mnts, then resided in a bachelor house with three guys.  It does dry well by bachelor standards.  But, it probably ranks at about a 4 on a 1 -10 scale of performance.  Which is fine for bachelors.


After 20 minutes with a probe in the lint trap.  the probe reached 135 F.  The room that the dryer was in was 53F.  Again this will dry your clothes.  It just does it in typical bachelor style.  The dryer is electric.

Black and Decker "Best Practices and Regulations"  copyright 01 says that:

for safe wiring to clothes dryer you can expect demand at 240V 16.5 to 34 amps = a range of 4000 to 8200 watts.
Mine falls at 240V @ 20 amps.  Even though my dryer works to my standards.  You can assume this old thing works far less efficiently now then most dryers you have ever seen.  So.... In its day this dryer put out

a very doable          * 17K btu*.

PS. My dryer costs about 50 cents an hour to run


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## Sting (Feb 18, 2008)

If I had edited out the one line about the fireplace ....

What else could you all find fault with???

Lets reserve the cloths line for the laundry - not for the hangman!

Eric - You scolded me for making non positive remarks! Do you school your favorites in a similar manor?


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## Nofossil (Feb 18, 2008)

ABGWD4U said:
			
		

> After 20 minutes with a probe in the lint trap.  the probe reached 135 F.



This temp is after the air has been cooled by the clothes. I'm absolutely certain that the air coming off the heating element is hotter than that, even in a bachelor quality unit. It's interesting that the commercial folks use 300 degree steam, but I also suspect that the air coming off of that steam HX is less than 300 - that would be pretty hot.

I got no reasonable way to stick a probe in mine. It's bolted to the top of our washer, and the WAF involved in moving it would be well into the negative numbers.

If 170 degree air is reasonably close to what you need, then it's probably possible to get that off of an automotive radiator. They give you quite a bit of surface area. If you need 250 degree air, then it's not practical in my view.


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## leaddog (Feb 18, 2008)

Sting said:
			
		

> If I had edited out the one line about the fireplace ....
> 
> What else could you all find fault with???
> 
> ...



I know that when people are on the net that sometimes things are written that are taken different ways. You can't see the person and not everyone is articulate (me ) so things don't get written the way it is intended. But that being said I see nothing here that hasn't been positive and I have enjoyed ALL the views on this subject as this is the way ideas can make things happen. Not every one is going to agree and not every ones math is right (mine usually) so we all have to take the posts with a grain of salt and get what knowledge we can.
leaddog


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## wdc1160 (Feb 18, 2008)

I will retest


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## wdc1160 (Feb 18, 2008)

Let me reitterate.  In my test.  I had no clothing in the dryer to cool the air.  Straight from element to the drum to the lint trap.  135F.
Isn't the conclusion we can use 180 degree water to dry the clothes?

I don't want to rip apart the dryer if I don't have to.


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## BrownianHeatingTech (Feb 18, 2008)

ABGWD4U said:
			
		

> Let me reitterate.  In my test.  I had no clothing in the dryer to cool the air.  Straight from element to the drum to the lint trap.  135F.
> Isn't the conclusion we can use 180 degree water to dry the clothes?
> 
> I don't want to rip apart the dryer if I don't have to.



Sounds like it's possible, then.  At least, to get "bachelor-level" dryness...

Joe


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## wdc1160 (Feb 18, 2008)

heheheh.   Did you guys really predict that the airtemp would be above 190?


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## BrownianHeatingTech (Feb 18, 2008)

ABGWD4U said:
			
		

> heheheh.   Did you guys really predict that the airtemp would be above 190?



The question is how much below that temp it will work at.  If the dryer can only work when the boiler is going full-blast to give peak-temperature water, it's not much of an interest to me.  If it can run on 150-degree water, that will be much more useful.

Joe


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## wdc1160 (Feb 18, 2008)

I see your point.  
I figure my 135 F air going into the lint trap probably does equal 150 degree water.  Any thing above that should be gravy.  Anything lower than 150 degree water = negative WAF.  
Judging by prior girlfriends,  my dryer is probably the equilibrium on WAF.  Any lower temp air and you will see negative WAF.  Higher temps are a certain plus.

I have used worse dryers than mine.  Sunday my dryer dried a large wet conforter in 1 hr.  I have seen dryers that would take 2 hrs for this large of an item.  Keep in mind this was in a 50F house which directly effects the relative humidity and the delta.

And, older dryers like mine are very large fire hazzards.  I think a 180F water conversion kit would make my old piece of crap safer.

I will test at the element


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## BrownianHeatingTech (Feb 18, 2008)

There probably is a niche market for high-efficiency water heaters that run off hydronic heat, with big building projects going for LEED certification and such.

Joe


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## mikeyny (Feb 19, 2008)

I have built a hydronic dryer and it works, but not too well or worth the effort. A standard dryer operates on much higher temps than you can produce with a wood fired boiler. The clothes do dry, but, it takes forever. I suspect that the cost of turning the drum and circulating the water costs more than the conventional way, not to mention the cost of the wood and the effort to load and maintain it. But then again, if you live off the grid, it would be well worth the effort. A wood fired cloths dryer could be ok, but ... a clothes line ... PRICELESS.     
                                                                                       Mike


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## wdc1160 (Feb 19, 2008)

Hey mike,   What is "much higher temps"  Have you measured temp inside  a dryer before?


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## Willman (Feb 19, 2008)

Great topic to hash over. From my dryer repair book "135* low temp to 165* high temp." Temperature is controlled by thermostats which are actuated by the timer. Snap type thermostats are usually marked as to which temp range they are. Heater cores or small rads from a car would work. Fab up an enclosure and utilize the 12 volt blower for air movement.The blower motor resistor could also be used for variable fan speed. For proof just check out the airflow and temp on your vehicle. I realize engine temps are greater, but are just a guideline.
My thought on a clothes dryer would be to capture and channel heat right from cabinet of boiler, possibly ducting off the stack with an air x air hx. My other thought was to build a cabinet near boiler to stack some wood in to make use of the latent heat from boiler. Hook up a small blower to move the air. Could do two things. Drive down MC and have preheated wood. Build the boiler room big enough for clothes and wood drying.
My electric dryer hasn't been used in years. We have 3 fold able wooden drying racks. Homes in the winter can use a little extra humidity. Clothes dry out overnight.No static snaps. Clothes lines are the best. I use mine on nice days in the winter. Guys if you want to increase the WAF throw the sheets in the laundry yourself and line dry them. Nothing like it. And I don't only mean the sheets. ;-)


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## Gooserider (Feb 19, 2008)

Interesting discussion...  I'm not sure there is a "right" answer, as there are a lot of variables.  It might help to try and break down some of the issues...  

First off - task analysis:

You have a washer full of X pounds of clothes, which are soaked with Y pounds of water that is left over from the spin cycle.  The drying job is to evaporate those Y pounds of water.  This is going to take so many BTU's of energy per lb, doesn't matter whether we are talking about cordwood, greasy coveralls, or the wife's unmentionables...  (note however that the X:Y ratio may change depending on the type of clothes) It also doesn't matter whether those BTU's come from solar / wind drying (aka clothesline) a rack in the basement, or a clothes dryer.  Call this the "key task" as you MUST accomplish it, or plan to sleep on the sofa due to low WAF.  :red: 

However all methods consume additional power in the form of delivering the BTU's needed for the key task - this is things like blowers, fans, dryer tumblers, the energy to drag that basket of clothes out to the line, etc.  Call this the secondary power consumption.  In the "perfect world" one would like to just use the amount of power needed for the key task, and keep the amount of secondary power to a minimum, but other issues such as time, type of secondary energy needed, WAF of the finished product, etc. is going to cause us to use secondary power to some degree.  As a working assumption, I think it's safe to assume that saving time, or increasing convenience will increase secondary power consumption.  Increasing WAF is likely to increase it as well, but this depends on the W (i.e. a preference for the feel of line dried stuff would lower it...)

The power for both the key task and secondary power can come in many different forms, some more suitable for different drying techniques than others.  In sticking with the question of a tumble dry clothes dryer, the secondary power would consist of the blower, the timer, and the drum turning motor, all of which are almost certainly going to be powered by electricity.  The power for the key task can come in any number of forms, most commonly gas (LP or Natural) or electricity.  

The question is whether we can replace the key task power with hydronics, and if doing so is worth the time and effort.  The secondary power is going to stay electric regardless, unless you want to hook up a belt to the wifes exercise bike (Caution, this approach is likely to have a LOW WAF!!  :lol: )

There are two or three parameters that would go into balancing out the choice of what we use for key power - availability, convenience, and cost of the different forms among other things.  There is also a desire to minimize the length of time it takes to do a drying cycle, as longer cycles are hard on the clothes, and the secondary power consumption is a function of time.  There is also the limitation that one can't apply excessive heat due to the risk of damaging the materials.

Now for some numbers...

1. I've read somewheres that the over temp cutout switch on most dryers is supposed to open around 180*F, which is consistent with Willman's comment that his manuals say desired operating temperature is 135-165*F

2. I know that the amount of electric power drawn by a gas burner is negligible, thus measuring the electrical consumption on a gas dryer should give a very close number for the secondary power requirement.  We have an older Whirlpool natural gas dryer, probably about 14 years old, fairly basic model, I would say about as typical as one is likely to find.  I just put a "Kill-a-watt" meter on it, and find I am drawing about 325 watts starting out with a large load of mixed clothes.  As the clothes dry, the power draw goes down (makes sense as the load gets lighter it should take less juice to tumble it) when the clothes were nearly dry I was showing about 275 watts.  This is a significant difference, but not a huge one, I think it is safe to assume a constant 300 watt secondary power consumption to keep the math simpler.

About 3-5 watts is the timer switch motor.  There was no noticeable change in the power draw between the Low, Medium and High heat settings. (which tends to confirm the negligible power draw for the burner assumption)

I forget for sure whether this dryer has a seperate motor for the fan, or if it just has one motor that both powers the fan and turns the drum, but I'm pretty sure it's the latter.  Either way, I think it's reasonable to assume that secondary power consumption 

3. The amount of moisture that can be removed by a given volume of air going through the dryer is going to be a function of the relative humidity of the air, which in turn is a function of the input air humidity, and how much / if the air is heated. It doesn't really matter HOW the air is heated.  (Exception - Gas dryers will add some extra moisture to the air as water vapor is one of their combustion byproducts, but I'm not sure how big a factor this is, probably not much)

As a corrollary of this, the heaviest, drippiest item will still dry on the "Air fluff only / delicate" setting if you just let it crank long enough.  Obviously this will reduce the amount of power consumed by the key task, but increase the secondary power consumption.  One could draw a graph showing the relationship between power consumption on the secondary side, and power on the key task side as a function of dryer temperature.  I don't know the exact curve shapes, but it is pretty obvious that as temperature goes up the secondary consumption would go down due to shorter drying times, and the key task consumption would go up due to energy spent heating the air.   Assuming there isn't a time issue, the logical "best" drying solution would be to pick where the sum of the two power figures (and costs) intersect.

4. According to some of the other threads here about doing water / air heat exchangers in HVAC systems, it was sounding like you CAN get 120-150* air from such an exchanger, which would work in terms of Willman's desired operating temp statement.  However secondary consumption might go up if you are at the low end of that scale.

Thus the key question IMHO is whether there are any savings in heat production costs (remember you have to power the boiler to make the BTU's, circulators, any extra blowers, etc.) and if that is enough to offset any increase in secondary power consumption.

Gooserider


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## mikeyny (Feb 19, 2008)

my dryer used a hot water heat exchanger made from an ac coil. It did actually work ok, but not while I was heating the house  and hot water. if I ran it specifically from the wood boiler only and made sure it was loaded with good wood it could keep up with the demand for hot air. Take into consideration the cost of wood, time, circ pump electricity and other things it just doesn't seem practicle. I am sure the whole thing could be designed and built more efficient to work better. Trying to get 150 hot air continuously into the dryer takes a whole lot of energy and wood. If the boiler stack was close enough that might be a better attemp to get hot air after the boiler is doing its primary job of heating the house. But you would still have to keep a good hot fire to get that stack temp up continuosly.

                                                                                                      Mike


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## leaddog (Feb 19, 2008)

goose------------- You are taking all the insentive out of this discussion and making this a practical discussion. All these inventive minds don't really want to save money, they want to have another reason to go out and cut more wood and use their boilers. Most of us don't have enough projects to keep us busy so we have to constantly think up more. But it don't make any difference I'm putting the dryer right there in the middle of my list. I just hope that when I get old I have got to that one.
leaddog


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## barnartist (Feb 19, 2008)

cute Dog.


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## Telco (Feb 19, 2008)

This is something I've also been interested in.  Sorry if this is a Master of the Obvious post, but I wanted to get my thoughts out there.  I've had the back of my electric dryer open, and found that the heating element is made up of 3-4 resistive elements inside of a thin metal casing, about 1.5 inch by 5 inch.  Not sure on the exact measurements as I was more interested in cleaning it out than building a water powered dryer at the time.  This metal case has a 4 inch round hole at the top and at the bottom of the dryer.

An automotive heater core is typically 6 inches by 8 inches by 1 inch, and can throw off a lot of heat.  Running 195 degree water through it is enough to raise the temperature of my truck's cabin to where it's summertime hot in just a few minutes, normally I heat the truck till it's comfortable then turn the dial over to mix in quite a bit of cool air.  In the summertime I have to kill water to the core because it's strong enough to overcome the air conditioner.  I don't have an automatic diverter on it.  The blower motor is close to the same size as the blower motor on the dryer, physically, so I'd have to assume that both push the same amount of air.  The cabin of the truck, however, is about 250 cubic feet, where the inside of a dryer is normally about 15 cubic feet, so that single heater core is heating a space about 16.6 times larger than we are interested in heating.

Based on this, seems to me that you could stack 4-6 heater cores together, one on top of the other, with the inlets and outlets connected so that hot water goes into the top one (output to the clothes) and comes out of the bottom one (sucks the last bit of heat out).  This could then be plumbed into the hot water supply.  The heater cores would need to be mounted inside of a metal cabinet that forces all air to pass through the cores, with a good filter in front of them.  This should produce enough airflow with more than enough exchange surface to heat the air by 150 degrees blowing into the dryer.  This box could be attached to the outside of the dryer to the metal panel, with flexlines connecting the water cores to the hot water inlet.  You would also need a standalone pump (and note the power needed to run this pump) to keep hot water moving through the system, kind of a closed loop type of thing.

If someone wanted to test this they could hook it up so that it took hot water from the washing machine water line, then dumped the outlet into the drain.  It would waste a lot of hot water, but if the clothes dried then it would be worth plumbing in water inlet/outlet lines to the dryer.  This is not something that I will be in a position to test for a couple of years, but if anyone else wanted to take a whack at it...


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## Sting (Feb 19, 2008)

leaddog said:
			
		

> goose------------- You are taking all the insentive out of this discussion and making this a practical discussion. All these inventive minds don't really want to save money, they want to have another reason to go out and cut more wood and use their boilers. Most of us don't have enough projects to keep us busy so we have to constantly think up more. But it don't make any difference I'm putting the dryer right there in the middle of my list. I just hope that when I get old I have got to that one.
> leaddog



Exactly If you could dry laundry with low air temps - appliance manufactures would only heat air to that threshold. 
Appliance cycle times at low air temps will not be cost or time effective - but it will keep the kids busy for a while. Time better spent hanging the sheets out in the sun!


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## Nofossil (Feb 19, 2008)

So it appears that the temps work out OK. Now for the economics for those of us who care.

Dryer heating coil is around 5000 watts. At $0.10 per kwh, 1 hour per load and 20 loads per month, over a six month heating season you'd spend about $60 on dryer electricity. Adjust for your situation.

I can scrounge a radiator and sheetmetal. I think the dryer's own blower would work. I have some PEX lying around. I'd have to buy some fittings, a zone valve, a 220V relay to drive the zone valve, and a high current 12v relay to allow the electric element to be enabled when I don't have enough hot water. My cost would be about $100 plus the labor to do the install. Couple year payback - not horribly bad.

Biggest issue is mounting the radiator and ductwork so as to not create negative WAF. Don't know how I'd do that yet.

Anyone have any idea if there would be potential corrosion issues with an aluminum radiator in a hydronic system?

I've attached a schematic for a possible control system.

R1 is a SPST 220vac relay that is activated whenever the drier wants heat - it's connected in parallel with the drier's heat coil.

R2 is a DPST 24vac relay that's energized whenever the hydronic system is hot enough as determined by the aquastat.

R2 disables the drier's heating coil.

If R1 and R2 are both energized, the zone valve opens, allowing hot water to flow through the radiator which is in a duct in series with the drier's heating coil.

If you're concerned about leaving R2 energized all the time, you could make R1 a DPST and put the second set of contacts in series with teh R2 coil. Then R@ would only be energized if the drier were calling for heat AND the water was hot enough. The downside is that the R2 contacts would arc every time, since current would flow through them for a fraction of a second every time the drier was turned on.

I think this might actually work.....


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## Telco (Feb 19, 2008)

Two things, what is WAF?  And, grounding the radiator will reduce corrosion issues, may even eliminate them.  When I was a youngster my dad was stationed in the Panama Canal.  Had a problem with the heater core on the family car pinholing every few months due to the high concentration of sea air.  One of the locals told him to ground the heater core, and this stopped the problem.  The same heater core was in the car years later when we sold it.  Any time I do a heater core now, I attach a ground wire to it, and ground the heater core to the body of the car.  

Ducting will be a bit of a problem in that you will have to somehow turn the air inlet to the elements so that it faces the back of the dryer instead of the front.  The element rack looks like it is made of thin aluminum.  Might have to just cut the bottom off of it, then use flexible duct that can go around the newly cut edge.  At least, this is how it is on my dryer, you'd need to verify flow directions, ect, on your dryer.


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## BrownianHeatingTech (Feb 19, 2008)

Telco said:
			
		

> Two things, what is WAF?



Wife Acceptance Factor or Wife Approval Factor.

In other words, attaching a clunky contraption to the side of a dryer, or "upgrading" the dryer to "only" take three hours to dry a load of laundry may not be well-received by certain members of the household.

Joe


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## Telco (Feb 19, 2008)

Heh heh... gotcha.  Very important consideration, that.


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## wdc1160 (Feb 19, 2008)

Nofo,  Isn't it copper with aluminum fins?


> Anyone have any idea if there would be potential corrosion issues with an aluminum radiator in a hydronic system?


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## Nofossil (Feb 19, 2008)

ABGWD4U said:
			
		

> Nofo,  Isn't it copper with aluminum fins?



Not for years, as far as I know. The ones I've seen recently are aluminum tubes and fins with composite plastic end caps. They work for a long time in cars, which have to be a worse environment.


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## wdc1160 (Feb 19, 2008)

nofossil said:
			
		

> ABGWD4U said:
> 
> 
> 
> ...



Agreed, cars have to be a horrible environment.  I don't know the implications of putting aluminum pipe in with black and galvan pipes.    I know that pex al is a aluminum plastic composite matierial with properties of aluminum, which is the closest I have seen personally to aluminum piping.

Maybe somebody can help us out here.


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## Telco (Feb 19, 2008)

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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## Gooserider (Feb 19, 2008)

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


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## barnartist (Feb 19, 2008)

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? BBBRRRRRfrom Ohio!


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## Telco (Feb 19, 2008)

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.


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## Nofossil (Feb 19, 2008)

barnartist said:
			
		

> 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? BBBRRRRRfrom Ohio!



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.


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## wdc1160 (Feb 19, 2008)

barnartist said:
			
		

> 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? BBBRRRRRfrom Ohio!




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.


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## barnartist (Feb 20, 2008)

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.


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## Willman (Feb 20, 2008)

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.


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## wdc1160 (Feb 20, 2008)

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


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## rsnider (Feb 20, 2008)

go to www.hardyfurnaceparts.com they have a hydronci clothes dryer u need. about 700.


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## barnartist (Feb 20, 2008)

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.


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## Gooserider (Feb 20, 2008)

Telco said:
			
		

> 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.



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


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## guy01 (Feb 21, 2008)

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


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## wdc1160 (Feb 21, 2008)

What does lead do to boiler equip???


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## steam man (Feb 21, 2008)

ABGWD4U said:
			
		

> What does lead do to boiler equip???



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.


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## Gooserider (Feb 21, 2008)

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


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## drizler (Feb 21, 2008)

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??


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## Willman (Feb 21, 2008)

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


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## BrownianHeatingTech (Feb 21, 2008)

Gooserider said:
			
		

> 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.



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

Joe


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## guy01 (Feb 23, 2008)

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


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## Gooserider (Feb 23, 2008)

Guy said:
			
		

> 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



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


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## Redox (Feb 24, 2008)

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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