Conference 7.286::home_work

    > Would some kind soul do the calc...?
    
    Better yet, would some kind soul post the formula??? 
    
    Edd

    Volume of a cylinder = Pi * radius squared * length
    
    3.14 * 0.5 * 0.5 * 120 = 94.2 cubic inches
    
    There are 231 cubic inches to a gallon�, so this is 0.41 gallons.
    You would need 50 of these ten-foot lengths to make twenty gallons.
    
    hth
    
    - Richard.
    
    � U.S. Gallons. The imperial gallon (U.K.) that I grew up with is 
    slightly bigger, 277 cubic inches.

Here are a few thoughts on what you are trying to do:

1) An interesting calculation would be to calculate the cost savings on raising
the water temp from, say 50 to 60 degrees before it enters the hot water tank.

2) How about using an old used electric hot water heater of say 40 gal capacity 
mouunting it near the woodstove.  Take the metal tank out of the insulation and 
trow everything else out.  

3) If you are going to use copper pipe why not use something like radiator
tubing that has a large surface area and is designed to transfer energy from
the ambient air to the pipe or vise versa.

4) My guess is that even with cheap materials the payback is going  to
take a long time.

Good Luck,
Wayne

    
    re.-1
    On the Same Idea.  You can get a steel coil insert to a wood stove
    to heat your water.  It require a few more gismoe's, but the
    stove is going so anyway...
    
    JD
    
    

    	Along the same lines as what someone already suggested, you may
    want to keep your eye out for someone getting rid of used baseboard
    heater sections. It would already have the fins on it.
    
    	Ray

    
      You'd better go deeper into the thermal calculations. The closer you
    get to the temp of the basement, the slower the rise will be. For
    example, if the water was 40 degrees and the basement was 70, the water
    in the pipe would heat up a lot faster than if the water was 50
    and the basement was 60. (On a time per degree basis)
    
      It is easy to figure out the *maximum* amount of energy you will be
    saving. Use the formula (x btu raises x amount of water 1
    degree) to figure out how many 'free' btu's you'll be getting from
    the air in your cellar. 
    
    ALSO:
    
   1.   Unless your cellar is extremely dry, you'll be getting
    condensation from all of those pipes. What will you do about all that
    dripping water?
     
   2.   Keep in mind that anything used to save energy/money needs a
    payback period of 10 years or less to be considered cost-effective.
    Usually an even faster payback is desired.
    
   3.   If your system actually works well, you'll be cooling off your
    cellar. That will increase your condensation and reduce the efficiency
    of the setup. (You have to get the heat from *someplace*)
    
   4.  You also have to remember that for there to be much heat xfer, the
    water has to be in the pipe for a while.
    
      Personally, I'd be very very surprised if this setup was
    cost-effective. Now if you have a NEED for it and don't care if it will
    pay for itself, that's a different matter entirely. If you can get it
    to do much.
    
    				Kenny

I have some literature on a stainless steel loop that can be used in my 
forced-hot air wood furnace (the furnace was designed and built to accept it).  
If I remember, I'll get the preheater manufacturer's name/contact information 
and post it here.

								-- Chuck Newman

     There is another note in here somewhere about this topic.  There are 
more details in that note but anyway ...

     It is cheaper to pick up discarded hot water heaters until you find 
one that doesn't leak [it took me two tries].  Remove all the insulation & 
locate near your hot water tank.  Whether its close to your main source of 
heat doesn't seem to matter -- that side of the preheater never feels warm.

     Condensation isn't that much of a problem.  You get some, and the 
first year you think your preheater tank is leaking, but it isn't.  In the 
summertime when you can get the basement up into the 70s, you will be 
getting up 20 degrees of preheat.  In the wintertime the preheat is more
like from 40 degrees to 50 degrees.

The manufacturer of my wood furnace sent me literature on the how water loop they
recomment.  It's made by:

Thermo-Bilt, Inc.
P.O. Box 3207
Schenectady, NY  12303

The installation instructions don't have a parts list, but from reading the
literature it's clear that it includes a stainless steel loop (3/4" schedule 40),
and a temperature/pressure relief valve.  It also implies that it includes a hole
saw.

The price for my kit would be $105.

								-- Chuck Newman

>    	C = Pi * D� * L / 924 

	    C = .4 gallons using 1" Cu tubing (with this formula).  This
	would not be a cost effective method of storing water.

	    Hot water only gets used a few times a day so the water has 
	between 8 and 15 hours to reach room temperature.  If the cold 
	water coming into the cellar lowers the temperature in the summer,
	that's great; free A/C!  In the winter, the wood stove keeps the
	temps. in the low 80's.  The water would absorb the heat when 
	the stove was burning and radiate the heat when the stove burns
	down.
	    It looks like I'll have to find some sort of storage tank. 

					Tim	
    

	Here's how I setup my preheater system. On the first floor kitchen is a
    combination wood/gas cook stove. Next to it on the firebox side there's
    a 20 gallon copper water tank same vintage as the stove. Instead of using
    the heater coil in the wood stove, I put it into the stove pipe exiting a 
    coal stove in the basement below. This set up works all by itself using 
    thermo siphoning. Cold water is feed out the bottom of the tank into the 
    low side of the coil. The heated water rises thru the coil up into the 
    middle of the tank. This warmed water rises to the top of the tank where 
    it drawn off to feed the gas hot water heater tank.
	There are shut offs to bypass the preheater tank and/or bypass the 
    copper coil in the stove pipe. The heater coil and the preheater tank each 
    have a pressure relief value, as well as drain downs and unions for
    quick disconnect and repair. 
	I get a 20 degree rise in the summer and up to a 60 degree rise in the 
    winter with the stove cranking. I opted to use the coal stove for two 
    reasons. I didn't want to lower the temp of the wood fire and increase 
    creosote build up and the preheater tank needed to be above the heat source
    by a few feet to take advantage of thermo siphoning.

	Another interesting thing I do to recover low grade heat is pipe the 
    water from the baths into a rack of (2) 55 gallons drums in the basement. 
    This gives the heated water about 2 day to give the heat up to the basement
    The cooled graywater is then directed from the low side of the bottom 
    barrel into a dry well out in the back yard. During the summer months the 
    water goes directly to the dry well. The washer machine water goes directly
    to the dry well year round. I got my wife to use cold or warm water
    most of the time for the cloths. If I could only get the kids to take
    cold showers. This has the added advantage of extending the life of the
    septic system by diverting large quanties of water, that doesn't need to
    be broken down, away from the septic tank. 
	Most of the plumbing was designed into the building when it was build
    except for the coil in the coal stove stack, so materials came in under $200
    and should last the life of the building with exception of the coil and
    maybe  the plastic barrels will gunk up and need replacement. I did
    luck out and get the 20 gal copper water tank and stand for $20 from a
    scape metal dealer. 
    
    
    
	And one more thing, of course I live in Tibet where dry wells and DIY 
    plumbing are perfectly acceptable!


	/Jim

And I thought I had a long commute!  I can't imagine commuting from
Tibet to HLO.

    
    With time to stop off at the "scape metal dealer" ta'boot!  ;^)
    
    Fred

    My electric hot water bill usually goes from about 30/Month during the
    summer to 50/Month during the winter. A couple of years ago I moved the
    water tank from the cold side of the cellar to the warm side, I heat
    half the cellar and the house by wood stove. That didn't make any
    difference in the amount of energy to heat the water. I then figured it 
    must be the temp of the water coming into the house, in the summer I 
    think the water is close to 70 degree's but in the winter I'd say it 
    around 55. 
    
    So what I did this past week end was run the feed to my hot water tank
    down from the ceiling around my woodstove flu pipe about 10 times and
    then back up into the ceiling and over to the tank. I have a couple of
    questions that I was wondering if anyone had any idea on.
    
    1. Could I build up extra pressure in the line by heating the water to
    much during times that we aren't using the water? The guy at the
    plumbing store felt that the blow valve on the water tank was enough
    protection but thought I wouldn't have any problems. 
    
    2. I noticed that without drawing any water, that after a couple of
    hours the feed pipe is pretty hot all the way to the water heater, this
    is about 20 feet and it goes up into the ceiling and then down to floor
    level to enter the water tank. Now I realize that hot water tends to rise 
    but I'm wondering if I'm getting a heat flow into the tank, I suppose 
    this would be good because it would help maintain the water
    temperature. Any idea's on what is accually happening here.
    
    I hope this at lease saves the $50 it cost be to buy the pipe. 
    
    
    Thanks for any idea's
    
    Alan

One suggestion unrelated to your specific questions: you may want to monitor 
creosote buildup in your woodstove flue a bit more often than before, since if 
you're drawing heat from the flue, you're likely cooling the smoke in the stack 
which can cause the creosote to condense more quickly.

If your stove is catalytic, this may not be so much of an issue. 

    
    
    Hummmmmm.......???    Why is your water so hot in the summer?
    Ground water should be in the high 50's....  If its 70, I would
    be a little conserned about what could be living in your water
    at that temp...
    
    Not a good Idea to put the pipe around the flue.  For one, i'd hate
    the agravation of cleaning the stove pipe.  
    Then there is the chance of overheating the water in the pipe and 
    causing excess pressure in the line.....  Need I say more....
    
    Preheating will cut down on your  heating bill.  They sell kits
    for a heat transfer coil that goes in your wood stove and then
    you'll need another tank, C-pump and pipe....
    
    JD

    
    I would say it depends on how much is "coiled" around the flue
    and whether or not the pipe actually makes contact with the 
    flue. I've seen a few articles on identical sounding setups
    that had the pipe in coil about a foot tall with a gap of roughly
    4"-6" between the pipe and the flue to reduce heat transfer.
    
    Better yet is to run a pipe out the lower half of the water heater
    tank, coil around the flue as described above, and return to the 
    upper half of the tank (I think I saw this in Mother Earth back 
    in the late '70s). This will allow convection to keep the water
    moving slowly to and from the water heater  (as opposed to the 
    possibility of heating standing water) 
    
    
    							- Mac
    

>    Hummmmmm.......???    Why is your water so hot in the summer?
>    Ground water should be in the high 50's....  If its 70, I would
>    be a little conserned about what could be living in your water
>    at that temp...
    
     Hot is relative.  You are correct that in the summertime the incoming 
water is in the 50s.  But in the winter, mine is 39.  Thats almost 20 
degrees colder.

     There are now a number of notes dealing with preheating hot water.  
At least two of the other notes talk about using an old water heater with 
the skins removed.  

    I guess I probably was way off with my water temp. I just knew that
    when I put water in the fish tank I didn't need hardly any warm during
    the summer to get 70 degree water, I will check the temp tonight.
    
    On the pressure build up in the system, does anyone have any facts or
    are these just guesses. I have a hard time believing that the pressure
    will build up all that much, the hot water tank has a blow valve that
    is rated at over 200 psi(I think) so I wouldn't think that it would ever 
    get close to that. I will keep an eye out for a used water tank, I
    could install it close to the wood stove and allow the water to
    circulate through it without much change to my setup. 
    
    As far as the creasole buildup, I'll have to see  how much it
    really builds up but I would rather have it build up there instead of
    higher up since it's easier to clean. I have a bit of a funky setup
    with my flu pipe because it runs up through a fireplace and then about
    6 feet into the chimney above the fireplace which is on the first
    floor, the woodstove is in the basement. 
    
    Thanks
    
    Alan

    
      I think what Ed was referring to is the pressure buildup you'd get if
    you *boiled* the water in the pipe. Since your pipe is outside of the
    flue, I'd say you'd have to really try to get that to happen, but it
    still can happen and if it does, the pressure in your system will
    skyrocket. This would happen if there was no hot water use for a long
    time and the stove was going pretty well. Of course, how long this
    would take is anybody's guess, *my* guess is that the stove would have
    to be going rather high >350 deg flue temp, for at least a an hour with
    no hot water use.
    
    				Kenny

    Well I found a used water tank last night, I was wondering how high I 
    have to mount it. Will the water circulate as long as the pipe going
    into the top of the storage tank is above the coil? Is is ok for the
    cold water return to be below the coil or should both be above the
    coil.
    
                              -----
                      |------|     |
                    Coil     |     |
                      |      |     |
                       ------|     |
                             -------
    
    
    Thanks
    
    Alan

Schematic:

          |-------Cold In  (note dip stick going to bottom of tank)
	  |   ___ Warm Out
	__|___|___
	| |	|				 Definitions:
	| |	--SO-----PRV---U--------|	 SO =Shut Off
	| |	|			|	 PRV=Pressure Relief Value
        | |     |                      H C 	 U  =Union
        | |     |                      a o 	 DDV= Drain Down Valve
        | |     |                      a i
        | |     |                      t l
	| |	|			|
	|  	--SO------DDV---U-------|
	---------
        Pre-Heater 
        Tank
    
 	The HOT return at the pre-heater wants to be higher than the
    coil on the flue. And the same goes for the cold feed to the coil. Without 
    the cold side gravity feed and warmed waters need to rise,thermo-siphoning 
    won't work good all by itself. You  must raise the tank or put in a 
    circulator pump. Typically the the heaters are located on the next floor 
    up. Or you can build a pedestal or MAYBE hang-it from the floor joist 
    over head. Which ever way you go, smaller is better, look for a 20-30 gal 
    pre-heater tank.
	You should find a  drain down valve at the bottom to use for the
    cold to the coil and a pressure relief value high on the side to use
    for the hot return from the coil. Be sure to insulate the long
    run of pipe you have to your electric heater. For best efficiently, setup 
    high enough right next to the wood stove. No Circulating controls also 
    means less down time.
    	Be sure to get a gate value which has a bleeder screw (for the
    inline shutoffs) to purge the air before you fire it up. Other wise,
    you'll blow the pressure relief value on the first firing. 
    That's the undesirable way to remove the air along with some Hot Water. 
    You only need to purge the air when srating with any empty coil.
    To get things started, close upper shutoff (gate valve type) and open
    the lower shutoff, then crack the bleeder screw on the upper shutoff 
    to purge the air. Next close the bleeder and open the upper shutoff and 
    now is time to light the fire.
    	To do flue pipe maintenance, close both shutoffs, open the drain down 
    valve and bleeder screw. Then disconnect both unions and you
    have easy access to the stove pipe. I'd check the chimney and flue pipe
    regularly, until you have a good understanding of the maintenance
    schedule the setup will require. Realize the moisture of the wood your
    burning will play a BIG PART in how often the pipe gets cleaned. This
    is a potentially ***Dangerous*** variable. I have a similar setup but
    burn coal and don't need to think about chimney fires.	
    
	With some quick hand calculations, it looks like you'll save your 
    electric bill about $1.00 per day on high output and ~ $.50 when the
    stove is just idling the time.the stove is on. So with heating days like 
    today(-17 deg F is morning in Oakham) you'll have the system paid for  
    in no time. That's assuming you don't charge yourself for labor. (_)

    
    electric 3400btu's/Kw     (30GAl X 9lbs X 50F X 2/day)/3400btu/Kw
    30 galtank			5.3KW * $.12/KW=.95
    1 gal H2O= 9 lbs.
    100F-50F=delta T 50F (High Output)
    80f-50F= delta T 30F
    cycle twice a day morning/evening


    Just another BTU miser,

    	/Jim

    Thanks a lot Jim, I'll let you know how things work out. 
    
    Alan

     Re: .8

     You're making a lot more complicated than it needs to be.  The
preheater is in series.  See note 1309.79 - 1309.last.

    
    re: .10
    
    		Your right, but I didn't complicated it. This was done when
    a Heat Exchange Coil was added to the wood stove flue. The setup in the
    base note does little more the raise the temp of a few gallons
    of water to high levels ~200F. It has no way to transfer the heat
    except when this is a demand for hot water. This is nothing more than a 
    poor length of baseboard heating with little benefit to the hot water 
    heating bill. By setting things up right, the efficiency to the Hot water 
    heater can easily improve by a factor of 10. This assumes there's not a
    constant demand for hot water. If this is the case, then approach in
    the base note will work good. In my case, which is probably the norm for 
    most people, we have a large demand early in the morning and again early 
    in the evening. If it's not, life styles can easily adjust to make a good 
    thing better.
     
    Regards,

    /Jim

    I opened the tank this weekend, it had some crap down the bottom which
    I would presume was quite normal, I rinsed it all out and it seems to
    hold water ok. Now when looking in with a flash lite there was some
    rust inside, should I throw this one away or do they all get rust after a
    little while.
    
    Thanks
    
    Alan

>    I opened the tank this weekend, it had some crap down the bottom which
>    I would presume was quite normal, I rinsed it all out and it seems to
>    hold water ok. Now when looking in with a flash lite there was some
>    rust inside, should I throw this one away or do they all get rust after a
>    little while.

Most tanks are supposed to be "glass lined" to keep the water out of contact
with the steel shell.  The glass lining, however, usually seems to fail at
some point resulting in rust patches.  Once the glass lining fails like this,
the tank becomes much shorter lived.

Stuart

    I'd rinse until it's clean. This tank won't see anymore high temps and
    should be good for a long time. If not they're easy to come by.
    
    
    	/Jim

    Well I got the tank installed this weekend and everything was going
    just fine until I put preasure to the tank. This is a gas water tank
    and there is a pencil tip size hole right at the very top inside the
    flue pipe. The only time water gets this high in the tank is when all
    the outlets are plugged and pressure is applied. Is there anyway to fix
    the hole or should I junk the tank? Even if I could patch it until I
    find another one. Someone mentioned lowering the water and trying to
    get some soder melted into the hole. 
    
    Anyway I installed it against the chimmney just to the back right
    corner of the stove, I left about 2 inchs between the corner of the
    stove and the tank. After about 6 hours the whole tank was pretty warm 
    top to bottom so this should work fine. I didn't put the coil around
    the flue pipe for a couple of reasons, (1) because it's a gas water
    tank and doesn't have the side outlets in the right place. (2) After
    reading a previous note I figured that I wouldn't gain all that much
    since I installed the tank so close the stove.
    
    Anyway hope I can patch it until I find another one. And by the way if
    anyone has a 30 gallon tank they don't want let me know.
    
    Thanks
    
    Alan

>... there is a pencil tip size hole right at the very top inside the flue
>pipe.  ...  Is there any way to fix the hole or should I junk the tank?
>Even if I could patch it until I find another one. Someone mentioned
>lowering the water and trying to get some solder melted into the hole. 
    
     Another possibility:  if you have taps you could drill out the hole,
tap it, and then plug it with a bolt.

    
    Sheet metal screw with some silicon sometimes work.
    Brazing the screw would be better.......
    
    JD
    

    Just as a point of interest, this morning I checked the water temp
    coming out of the bottom of the tank, it came out at 100 degrees. (not
    bad for the bottom) I got that tempurature even after the fire had long
    since burned down, I filled the stove last night at 10pm so all I had 
    left was coals. I'm sure I could get a bit higher temp when the stove
    was cranking
    
    Alan