Anyone ever try this setup or similar one for heating domestic hot water with wood stove?

[NH_Wood]

Hi all,

I've been interested in ways to cut down on oil bill - we only use oil to heat our domestic hot water and I HATE to hear the burner kick on! Looking for a way to at least minimize the need for the boiler to bring cold water up to temp. Here is the link to the set up I'm thinking of - I DO NOT want to add a heating coil to the interior of the fire box - this set up seems a good alternative and apparently does not result in lowers firebox temps. What do you all think?

(broken link removed to http://www.motherearthnews.com/Do-It-Yourself/1984-01-01/Add-Water-Heater-To-Stove.aspx)

Cheers!

 

[hareball]

In the 70's My Father used the radiator from a car mounted to the back of the stove and it was sent to a holding tank in the utility room.

 

[begreen]

Whatever you decide, do it very safely. Steam is a mighty force that needs great respect.

You might want to take a look at John Gulland's system. Maybe chat with him if you are serious about building one.

http://www.gulland.ca/homenergy/stove.htm

Also, the folks in the boiler room here may be helpful in discussing safety precautions and hardware considerations.

 

[NH_Wood]

BeGreen - thanks much for the info - will look into this. Cheers!

 

[savageactor7]

I think that's a great idea...unfortunately my wife don't want any part of that.

Mother earth news RULES!!

 

[webbie]

I've used and made up ones similar to this.

Back then I found a shop that made finned coils for boilers - like for DHW - and had them bend serpentines for me to fit on the outside of a stove.
It also could be done using silver solder and U fitting, although a finned coil would seem to pick up heat best.

I often set these up in combo with a solar tank, with the electric element in the tank providing backup.

Here's a hearth.com article
https://www.hearth.com/econtent/index.php/articles/domestic_dhw

 

[WES999]

The first thing i would consider is to get rid of the oil furnace for heating DHW. (I am assuming you have a tank-less coil on your furnace). I had a tank-less coil and switched it for an electric an electric water heater. The monthly cost went from about $80/mo with oil to $25 with electric.

That said, I just finished up a wood stove water heater similar to the one in the link.
Some of the key features of my setup is, I used 3/8 OD ridged copper tubing sandwiched between two pieces of 3/8 aluminum with groves milled for the tubing for the HX.

Also my set-up is non pressurized, there are 2 55 gal drums with a circulator pump controlled by a temp controller. A TC probe is inserted in the HX on the stove. I have a TP relief valve plumbed to the HX.

Cold water is heated as it flows through 4 100' coils of pex in parallel (2 in each barrel) and then flows to the input of the electric hot water heater.

I only have had the system running for 2 days but so far the hot water heater has not turned on yet.

I plan to add 2 4' X 8' solar collectors in the future, I have one about half finished.








with 200' of 1/2 pex

 

[jtp10181]

WES999, so the stove heats the water in the drums, and the drums heat the water in the PEX?

 

[WES999]

Exactly, It is the same design that Gary used in his solar water heating system.

http://builditsolar.com/

The stove heats the water in the tanks and and DHW is heated as it flows through the pex.

The tanks are up to almost 150 °F right now.

The pex does a good job transferring heat, the temp exiting the tank is only a few degrees lower that the temp in the tank.

 

[NH_Wood]

Thanks for the info Craig and for the info and photos Wes999. What do you think about the ability to do something like this using a soapstone stove? Exterior stove temp will be lower obviously, so less heat to coil, but would still reduce my need to heat cold water from the well if I run it through this first. A question was asked about my oil furnace - running a Burderus with a hot water tank - so.....I get fairly upset hearing the oil burner kick on just to keep water hot for showers, laundry, etc. etc. I'd like to have a system that might cut down the oil by even ~ 50% - not looking (nor would I get) full DHW from a stove. Thanks again! Cheers!

 

[WES999]

You may find this interesting:
https://www.hearth.com/talk/threads/39434/
Replacing the oil fired DHW heater with an electric ( or gas if it is available)
may be the most cost effective thing to consider.

I think if you want to have your wood stove pre-heat DHW you would need a tank type heater anyway.

What temp does the soap stone top usually run at?

On my Fisher the stove runs quite hot, with a good load of dry wood it can spike up to 750 °F -850 °F .

Obviously a lower stove top temp would provide less heating.

 

[NH_Wood]

Wes999

I think the Hearthstone Mansfield stovetop (but the back is where I'll but the exchanger) usually will top at ~ 500* (I don't have it yet - planning on an install in March). I'm guessing the back of the stove will be a little lower. I'm thinking about running the coil to an old hot water tank (no working element), and then feeding the hot water to the oil boiler tank inlet, rather that have the ~ 40* well water enter the hot water tank. This way, I'm hoping the oil might only have to heat perhaps 90* water (just a guess) to normal temps, rather than 40* water. I'm hoping that might result in perhaps 40-50% savings on oil. I guess it will just depend on hot hot I can get the water from the stove. Since the stove is large, I think I can get a 60' coil of copper tubing along the back. Do you know what type of flexible copper tubing to use? I was online checking out coiled copper and there is refrig coil, K and L coil, etc. I'm no plumber! Any idea if one type or the other is best for this app?