Has anyone used a standard heat exchanger for heating water

[squarpeg]

Getting ready to install my plumbing. Always wanted to try heating my water with woodstove. I am off grid. My only heat is an old smoke dragon in the basement. I wanted to do a thermosiphon system through some type of heat exchanger. i can't find any being specifically made for woodstoves. From research people put a copper coil in the stove pipe, or around it. I am reluctant to do that only because of dropping the stack temperature. I have a 25ft exterior chimney. Considered DIYing something out of copper pipe on back or side. Then thought why not buy a real heat exchanger and set it very close to the side of the stove. Something like this:

https://www.amazon.com/GPOAS-Exchan...P216/ref=cm_cr_arp_d_product_top?ie=UTF8&th=1

The smoke dragon runs at 700 degrees a lot, It is hot even 6 inches from the side of the stove. Wondering if this system could work. Thoughts?

 

[begreen]

It's designed to extract heat from its internal tubing and exchange it to the air aided by the fins to maximize air transfer. I think this would be inefficient compared to something that puts the pipes directly in contact with the stove body or runs through the firebox with stainless piping.

There are a few thread here on thermosiphon systems. John Gulland also wrote about his customized stove that had hot water heat extraction.

Clean Cook Stove

 

[squarpeg]

Not saying your wrong. I have determined I don't really want pipes in the stove. Also considering soldering copper pipes to a steel plate then placing that behind the fire box. so pipes are sandwiched between steel plate and the stove. Not integral to the stove but you could place it right against the back of the stove. Would think the pipes should be brazed as opposed to soft soldered. ?

 

[begreen]

Not saying your wrong. I have determined I don't really want pipes in the stove. Also considering soldering copper pipes to a steel plate then placing that behind the fire box. so pipes are sandwiched between steel plate and the stove. Not integral to the stove but you could place it right against the back of the stove. Would think the pipes should be brazed as opposed to soft soldered. ?

Yes, it doesn't have to penetrate the stove sides. A pipe loop attached to the side or back of the stove could be effective. I'm not sure about using copper. It would be good for heat transfer, but there may be an issue with dielectric corrosion.

 

[all night moe]

No to soft solder. It may let go under high heat conditions. Brazing would work.
I agree with begreen's post above about possible corrosion. Something to look into.

 

[squarpeg]

How about this idea. You put a big pot of water on the top of the stove with a coil in it?

Amazon.com

 

[all night moe]

How about this idea. You put a big pot of water on the top of the stove with a coil in it?

Amazon.com

It works. The bigger the pot the better recovery times will be. Gotta keep it fed too.
What are you heating the water for? DHW or added hydronic heat?

 

[squarpeg]

Just domestic hot water for my wife and I. Dishes and Bathing is all that is needed.

 

[all night moe]

There's a lot behind all of this. Mixing valve to prevent scalding, pump and FPHX, or sending cub water through the coil before water heater? Each has it's pros and cons. Any setup with a wood stove will not keep up with demand. Best to leave water heater functional as designed. It will kick on when stove can't keep up. All in all, it's usually not worth the effort.

If you proceed, keep us posted on your findings.

 

[Todd]

The first year I was off grid we just used an 8 gal stainless pot on top of the stove that had a spigot. That water stayed warm for many hours after the fire was out.

Now we use an on demand propane water heater hooked to a pump and 65 gal water tank.

 

[squarpeg]

I did manage to come across someone that will make one for you. This is not a recommendation, had no interaction with this site, Just info for others : https://toastybear.neocities.org/

 

[3650]

 

[all night moe]

View attachment 334422

That works when the stove is close to the water heater. Water can easily get overheated if, stove is running hard and hot water isn't being used.