What do you folks think of the idea of retrofitting a wood stove to also heat water?
Here is a web site that purportedly will do this:
http://www.hilkoil.com/product.htm
My original thought was an alternate way to heat water for a hot tub (to supplement the main source).
mt
Interesting. Looks like it should work.
When I was a kid, I remember my parents had a sauna with piping rigged in the fire box to do the same. The pipes failed either because of poor quality or because there was no water in the lines. I don't know what the cause of the failure was.
The stuff you are looking at is stainless steel so that should be better. Might be a good idea to ensure water is always in the lines so the metal doesn't get red hot.
I haven't had a stove I thought the fire box was big enough to start with much less add something else in there. ::). I have thought about running a couple of lengths of pipe up the flue pipe though, Would be much easier to put holes in flue pipe and no loss of space. Or maybe wrap some copper tubing around the flue pipe on the outside, That would be real easy :) not to mention alot cheaper ;)
The stoves I used to build had an optional stainless steel water heater insert. It was around 8x8 like corrugated metal roofing with a space between two layers. I didn't ever install one in the stoves I made though.
Pipe in the flue? Might be more difficult to run the chimney sweep brush through.
Seems John did one around the outside of his stovepipe.
I have to clean my stove pipe several times per season --- did it tonight as the creosote condenses on the pipe getting out of the ground - the pipe is always pretty cool.
I could see a coil on the outside of the pipe, if it could be made presentable enough. You could maybe do it with soft copper tubing. ???
Do be careful of letting dissimilar metals touch in a flame or in a wet environment.
-f-
They could be made to look very nice....
(https://i35.photobucket.com/albums/d184/glennkangiser/2200543253_6ccdfd7b55.jpg)
I had one of these in my old cabin. Five gallons at a time worked well. I made mine out of stainless. Attach to the stove or sit it on the top.
Just lift the lid and fill her up.
(https://i455.photobucket.com/albums/qq278/Minermatt/waterheater.jpg)
Quote from: glenn kangiser on November 13, 2008, 11:32:02 PM
Seems John did one around the outside of his stovepipe.
I have to clean my stove pipe several times per season --- did it tonight as the creosote condenses on the pipe getting out of the ground - the pipe is always pretty cool.
We burn about 5 to 6 cord a winter (our main heat source) and when I clean out our 8" X 12' flue pipe I only get about a cup of carbon ash and the only creosote accumulation is right around the rim of the rain cap, None inside the pipe.
I only have to clean (inspect!) ours in the fall before I fire it up. Aside from the rear exit from the stove I don't use any horizontal runs in the pipe. By keeping as much of the pipe in the heated part of the house as possible it helps the pipe stay hotter and keeps creosote to a minimum. I have put my Blue Point temp. gauge to the pipe before and in the first 2' got readings between 200 to 400 degrees with a normal fire.
When I lived in Ca. I thought my creosote problem was from burning pine but I burn some pine here and the only real difference I have noticed here was after I quit running my pipe outside then up on the outside of the house. We also had more creosote with our air-tight stove but still not enough to warrant cleaning more than twice a year. I guess it could have something to do with the minerals in the soil, Out West I think the salt content is much higher. ???
On mine it is because 3 feet behind the stove it goes underground -- stovepipe buried in dirt - single wall for about 6 feet - it goes horizontal then uphill. Doesn't everybody live underground?
We had the same problem in France when we stayed in the cave. It took a bit to get the fire to start drawing as the popi was cold and went through about 15 feet of rock and soil.
Quote from: MountainDon on November 13, 2008, 11:01:17 PM
Pipe in the flue? Might be more difficult to run the chimney sweep brush through.
About the same as cleaning the soot from a diesel fuel fired steam cleaner ;D d*
My original idea was to sandwich the pipe in an envelope to keep the pipe from direct contact with the soot and ash as it is corrosive. My biggest concern and main reason for not trying one is the thought of a steam pocket building in the line and blowing out scalding my family. If the water wasn't constantly circulating it could over heat very easy. Even with schedule 80 or better pipe the "U" bends are a weak place especially when in direct contact with flame :o.
It is way to easy for me to over fire a wood stove so I tabled the idea and just heat the water on top of the stove in my turkey fryer pot ;).
Quote from: glenn kangiser on November 14, 2008, 10:42:05 AM
On mine it is because 3 feet behind the stove it goes underground -- stovepipe buried in dirt - single wall for about 6 feet - it goes horizontal then uphill. Doesn't everybody live underground?
We had the same problem in France when we stayed in the cave. It took a bit to get the fire to start drawing as the popi was cold and went through about 15 feet of rock and soil.
Yep, Cold pipe! Just have to live with the pipe cleaning ritual. Oh well I am sure it's worth it :) :) :)
Yes - I don't mind too much- I just pulled a plastic stove pipe brush through it with a rope - bucketed the big stuff and sucked the little stuff up with a shop vac. I have a tee cleanout outside and can poll the elbow and 3 feet of pipe inside easily. Takes about 20 minutes total.
My vertical pipe turns to tin foil after about 3 years and I have to replace it but it's above ground.
Quote from: glenn kangiser on November 14, 2008, 10:57:41 AM
Yes - I don't mind too much- I just pulled a plastic stove pipe brush through it with a rope - bucketed the big stuff and sucked the little stuff up with a shop vac. I have a tee cleanout outside and can poll the elbow and 3 feet of pipe inside easily. Takes about 20 minutes total.
My vertical pipe turns to tin foil after about 3 years and I have to replace it but it's above ground.
My Grandpa said he used to close the damper and drop a long haired cat down the pipe :o He said by the time the cat clawed it's way back out of the pipe it was squeeky clean, I figure he was talking about the pipe being clean ;D ;D ;D
Never a dull moment around him! :)
rofl
Quote from: MikeT on November 13, 2008, 06:28:54 PM
My original thought was an alternate way to heat water for a hot tub (to supplement the main source).
Is the hot tub already wood fired?
Japanese wood fired hot tub heater
http://thesolar.biz/Chofu.htm (http://thesolar.biz/Chofu.htm)
www.cowboyhottubs.com/
For the non-plumbing folks. ;)
Too cool! Water the livestock and play in the hot tub at the same time. rofl [shocked]
Quote from: MountainDon on November 13, 2008, 11:01:17 PM
Pipe in the flue? Might be more difficult to run the chimney sweep brush through.
I think if you started out with a 7 or 8 inch pipe to put your heat exchanger in say the frist 24 inches and then necked it down to a 6 inch with a reducer you would be fine.
A snorkel wood fired hot tub came with our property. Haven't tried it yet, since it needs a little work. You definitely need to plan ahead, since it takes awhile to heat it up. But, I can't wait to try it. There's something to be said for anticipation!
Here's a link:
http://snorkel.com/index.php
I was also looking at a solid cypress tub to use as a regular bathtub--talk about pretty--but it sounds like it may not last for more than 5 - 10 years, especially if you use soap.
Nothing to do with the water issue, but every so often, I just bang on my flue with the palm of my hand open, and you can literally hear the build-up breaking free and dropping into the stove...then scoop it out before firing....I do this before firing, ofcourse....when I say bang, I mean GENTLY.....might go ahaead and brush it this week though just to be sure.....here Kitty Kitty....... ;)
CREATIVE1 a friend of mine who is off grid has one. Uses it daily. His is an older model and he said he needs to re-order the wooden stays. He bought his 2nd hand several years ago. If you can make a cover with rigid insul it will keep the heat better and required less time to heat up.
Came with one of those too, plus about 20 spare staves, etc. Have to fix the inside bench.
I added a water heater to my wood stove this past weekend.
(https://i133.photobucket.com/albums/q75/djmillerbucket/jemez%20mountain%20property2/mini-P1000463.jpg)
;D ;D ;D
On the topic of wood-powered water heating...
We have a simple thermal-siphon system set up on our rocket stove (http://www.rocketstoves.com). Our water heater tank is elevated on a platform, just a few feet from the stove. We put a tee on the drain valve of the tank and ran a line up to a copper coil on top of the stove. From there it goes up to the top of the water tank and tees into the hot water out line. We made an anti-siphon device to prevent sucking cold water through the coil from the bottom of the tank when the stove is not in use.
The system is nice because we didn't have to modify or compromise our new water heater in any way. BUT, there is a big drawback... All of the steaming hot water likes to sit right on top of the tank (naturally, since that's where it's coming in). So, we get about 5-10 minutes worth of scalding hot water, and then nothing but cold.
The simplest fix is to come into the side of the tank with the hot water, rather than the top. But, we're not about to cut a hole in the tank... So, can anyone think of a solution to this problem, short of cycling the water with a pump?
May work - may not but how about custom making an extended nipple to go down inside the water heater about half way -maybe solder or braze a piece of copper pipe into the cold inlet of the heater and put the hot from the stove in there to mix with the other water. The hot would still go out the hot side of the heater.
Going from how I think it is setup, Andrew - pix or drawings could help if I don't have it right.
You did it again!! Thats what I was thinking, Just continue the tubing down into the tank rather than terminate it at the top. Provided it's smaller tubing.
Doesn't the cold inlet usually extend down into the tank like you're describing? We tee'd into the hot line, based on some instructions I read.. Not really sure why.
Would the hot water actually go down through the pipe, or would it just stay at the top since it's less dense than all the colder water around the pipe? Or perhaps it would get sucked down regardless, since water's leaving at the bottom of the tank and has to be displaced?
If you want some visuals, here's the site that we got most our info from: http://www.green-trust.org/2003/fireandwater.htm
You need to get up a couple minutes earlier or type faster cordwood.... [crz]
Perris High School and dial up = SLOW. Not my fault :-\
If the heated tubing line still terminated higher in the tank than it started it should still siphon. And if you came in the hot outlet opening in the top of the tank but did not obstruct it it should still allow hot water out to the rest of your plumbing. A tee in the top of the outlet you could sweat a reducer to the tubing to seal small tubing inside larger tubing and then go through the tee.
Your hot line from the stove should be tee'd into the cold supply line to the water heater tank for this to work. Glenn is on the right track but the work was already done for you at the water heater factory. The cold line in the tank has what's called a "dip tube".
(http://static.howstuffworks.com/gif/water-heater.gif)
(http://static.howstuffworks.com/gif/water-heater-labels.gif)
I haven't researched it that well, Andrew. I'm just trying to figure out a way to get it to mix better in the tank. It stratifies in the tank if not mixed well enough.
There you go -- Don has the straight poop on it. :)
Perris--- I worked there at least once, cordwood. Putting Roll Bars on Caterpillars -
Quote from: MountainDon on November 18, 2008, 11:59:21 PM
Your hot line from the stove should be tee'd into the cold supply line to the water heater tank for this to work. Glenn is on the right track but the work was already done for you at the water heater factory. The cold line in the tank has what's called a "dip tube".
Yeah, that's what I thought... Sure seems smarter to feed the hot water into that line. Any idea why that site has you go through the hot? It was the most thorough guide I had read on the subject, so I figured the author knew what he was talking about.. ::)
Maybe when you experiment with it you will be able to come back and tell us. :)
It may slow the thermo-siphon as the heated water will be closer to your drain but it should immediately rise mixing on the way as it is so hot, but again it may not want to pass through the cold.
Quote from: MountainDon on November 18, 2008, 11:59:21 PM
Your hot line from the stove should be tee'd into the cold supply line to the water heater tank for this to work. Glenn is on the right track but the work was already done for you at the water heater factory. The cold line in the tank has what's called a "dip tube".
(http://static.howstuffworks.com/gif/water-heater.gif)
(http://static.howstuffworks.com/gif/water-heater-labels.gif)
Teeing into the cold line might work good when there was demand on the hot side circulating the water, But at rest I think it would be too close to the bottom for a good heat siphon effect.
By making your own dip tube on the hot side it wouldn't cool as fast on entry either.
What about the blow off valve? Could you go in there? Is it seperate?
Yes, it's separate. Judging by the pics it looks like the hot line already has a little dip tube, but perhaps that varies by model.
The hot and cold nipples on our heater have little plastic strainer type things that would have have to be removed in order to extend a tube down inside the tank. Not knowing anything about water heaters, we didn't want to mess with them at the time since it looked like they were supposed to be there. It sounds silly, but do you have any idea what I'm talking about or if we could remove them?
I've seen them - I don't think they are removable.
I don't think the T/P valve would work as it needs to be there unrestricted for safety.
How about a separate tank on the ceiling with switching valves to cut it out when there was no heat or ... You could tee it into the existing lines - maybe just send your cold to it first then let the regular heater finish the job if necessary.
Send the output of it to the cold of the main heater.
If I remember right those are corrosion isolators and I have actually had to remove the one in the tank we have now because it deformed and blocked the flow d*
I am not sure how it would work with the blow off valve because a tee would take the thermal part of the valve out of the water if an air pocket were to form in the tee/valve. For a dip tube to work there it would have to go straight down and that would put the valve on the horizontal of the tee, Witch should still work but it would have to have a nipple to make room for the thermal probe on the valve.
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. I see a scalding experiment in my future [scared] [crz]
Thanks for clarifying what those things are, cordwood. Another mystery solved... (We live in a cordwood house, btw. :) )
The tank is only a foot or so from the ceiling, so we don't have room for your idea, Glenn. Thanks for the help, though! Seems like there is no easy fix for our situation.. I can't really complain about the system, though, considering how simple it is.
My thinking was, and is, if the way it is plumbed at present produces the problem with very hot stratified at the top, something must be wrong. The simplest thing seemed to be to switch the position where the hotter/warmer water re-enters the tank.
If it was me, I'd plumb a new Tee into the cold, leaving the Tee at the hot, but plugging it. Then switch the hot line from the stove to the cold inlet Tee on the tank. Let her rip and see what happens, all the while monitoring the temperatures.
I notice the article makes verbal mention of a tempering valve, but it is not illustrated. Could be the source of the problem you are experiencing? ??? I don't really think so, but I'm grasping at straws here.
Here's another straw... If the hot water is stratifying at the top, it's too hot there, you don't have enough circulation within the system. The model T Ford used a thermosyphon cooling system. So I believe this must work and work as drawn, but your flow rate is too slow to mix the water in the tank well enough to temper the temperature throughout the tank.
Bigger pipe? Does the cold loop between the tank and the stove have a downward slope (from tank to stove) with no dips or rises that would impede the flow?
Quote from: MountainDon on November 19, 2008, 01:39:27 AM
Here's another straw... If the hot water is stratifying at the top, it's too hot there, you don't have enough circulation within the system. The model T Ford used a thermosyphon cooling system. So I believe this must work and work as drawn, but your flow rate is too slow to mix the water in the tank well enough to temper the temperature throughout the tank.
Bigger pipe? Does the cold loop between the tank and the stove have a downward slope (from tank to stove) with no dips or rises that would impede the flow?
I've worked on a few old tractors with thermosyphon, Usually a blown headgasket from over heating d* ;)
The drawings say not to go up,over and down,........But all the drawings go up,over and down ??? ??? ??? ???
... or there's not enough vertical separation between the tank and stove to get a good thermosiphon action happening. ???
Here's a very basic sketch of our setup:
(https://img.photobucket.com/albums/v667/AirsoftAndy/rocket-water-heater.jpg)
The coil position is not ideal due to the height of the rocket stove, but we got the tank as high as possible and should have enough separation based on what that article says.
Unfortunately, the water heater is in a very cramped closet and is difficult to work on (house design boo boo), otherwise I would tie into the cold line just for the heck of it and see what happens like you suggested. I do have a feeling that the thermosiphon action would suffer from that though, depending on how far down the dip tube reaches... ???
I think you are likely right.
On thinking it over and seeing your drawing I'd guess that the point to point plumbing is fine, but the thermosiphon action might be slowed down by the height limitation for the tank and all those 90 degree turns. ???
How hot does the hot pipe from the stove to the tank get?
A very small circulation pump would likely do wonders for evening out the tank temperature.