retrofitting a wood stove to heat water

Started by MikeT, November 13, 2008, 06:28:54 PM

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MikeT

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

MountainDon

Just because something has been done and has not failed, doesn't mean it is good design.


Rover

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.

cordwood

 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 ;)
I cut it three times and it's still too short.

glenn kangiser

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.
"Always work from the general to the specific." J. Raabe

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MountainDon

Pipe in the flue?   Might be more difficult to run the chimney sweep brush through.
Just because something has been done and has not failed, doesn't mean it is good design.

glenn kangiser

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.

"Always work from the general to the specific." J. Raabe

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MountainDon

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.   ???
Just because something has been done and has not failed, doesn't mean it is good design.

NM_Shooter

Do be careful of letting dissimilar metals touch in a flame or in a wet environment. 

-f-
"Officium Vacuus Auctorita"


glenn kangiser

"Always work from the general to the specific." J. Raabe

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Whitlock

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.


Make Peace With Your Past So It Won't Screw Up The Present

cordwood

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. ???
I cut it three times and it's still too short.

glenn kangiser

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.
"Always work from the general to the specific." J. Raabe

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cordwood

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 ;).
I cut it three times and it's still too short.


cordwood

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 :) :) :)
I cut it three times and it's still too short.

glenn kangiser

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.
"Always work from the general to the specific." J. Raabe

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cordwood

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! :)
I cut it three times and it's still too short.

glenn kangiser

"Always work from the general to the specific." J. Raabe

Glenn's Underground Cabin  http://countryplans.com/smf/index.php?topic=151.0

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CREATIVE1

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?

MountainDon

Just because something has been done and has not failed, doesn't mean it is good design.


cordwood

I cut it three times and it's still too short.

alcowboy

Too cool! Water the livestock and play in the hot tub at the same time.  rofl [shocked]

Whitlock

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.
Make Peace With Your Past So It Won't Screw Up The Present

CREATIVE1

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. 

jb52761

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....... ;)