Converting my Stove into a Hot Water Heater

[Shortwave]

I live in upstate New York, near pine trees, and an abandoned, moss-covered loose stone wall running through the forest, marking some forgotten farmer's century-old property line. Not everyone is lucky enough to live in rural America. This is a question for those who do.

I have an electric water-heater, the 50 gallon size. Also I have two stoves I use for heating the house. In the basement is my wood stove. My rice coal stove is in the living room.

The only purpose ever for these stoves has been to heat the home. Then I found a website, http://www.hilkoil.com, offering a new kind of water-heater. Instead of using gas or electricity, it uses excess stove heat, from any kind of stove. Should I install this new water-heater in my woodstove?

They call it a "Thermo-Bilt Coil", and it's a loop of stainless steel. It actually mounts inside the stove. If I cut two holes in the side, near the stovetop, with the hole saw bit included in the kit, that will put the steel loop where the stove has the hottest temp.

The whole kit costs less than $200. I'm not the handy type, so I will need a contractor. Thermo-Bilt provides a good set of instructions, but what questions should I ask my contractor to make sure he's the right man for the job?

Because my hotwater tank is on the first floor, and my woodstove is in the basement, my plan is to take advantage of natural water circulation, the cold flowing downhill from the bottom of the tank, then rising after it's heated in my stove, and it returns hot, and is released in the top of my tank. I guess this happens over and over, until my water gets to the same hot temperature I'm used to. (I heard some people put their tank in the attic, just to take advantage of this.)

I do not want to abandon my regular water heater completely. When I'm not using the stove, I can turn on the electricity breaker for my hotwater tank. But I would love to stop paying the electric company, and get free hot water for the whole winter.

 

[jtp10181]

You will cool off the flue gasses which will create more creosote in the flue and probably lead to a nice chimney fire. Not to mention you will be DRILLING HOLES in your firebox.... doesn't this seem like a bad idea?

 

[Shortwave]

Hey jtp10181, thanks for the reply.

No, I don't mind pimping my firebox. I'm looking forward to doing that part myself.

I never considered the effect on flue gases. I've been researching this for a couple months, and I never came across any mention of creosote problems.

Do you speak from experience?

 

[webbie]

Short, a couple comments:
"New kind of water heater"....hmm, these have been around since I have been in the business - about 30 years, and probably much longer! Nothing new, under the sun...and surely not heating your DHW. I can assure you that I have installed this type of device in rural, surburban and even urban America....

Secondly, as you must know if you have been researching things, there are various brands and types of units available. For instance, a nice unit is the Yukon Hotrod, which has the substantial advantage of being able to be installed with only ONE hole.

Also, as jtp mentioned, there are various options which allow you to get some DHW without drilling into your box. Some of these options can also be safer.

Your post sounds a bit like an advertisement.....are you connected with the company in any way?

 

[fish]

i would suggest that you take a look at woodheat.org they have a great artical on heating water with the wood stove. there are many different designesjust like the web master stated. i would say the safest is a set of coils in a box that mounts to the stove under the heat shield. ( for a stove with a heat shield) also in the same arcticle they show what can happen when heating water with a stove. and its not good.not to mention once your insurance co finds out you hooked up water to your stove theres a 90 percent chance they will drop you. i was thinking about doing the same thing but youll still need a hot water tank. i ended up just bying and installing a tankless water heater much more space efficent . i mounter mine in the actic. and it works great verry easy to do. good luck

for 200 dollars for the parts and atleast another 200 in pipes and installation. also dont forget a heat pump for circulation. and what about a release valve

 

[kellog]

I looked into this type of set up years ago and decided it was not the right thing to do for many reasons including all of the above. I agree you should look at woodheat.org. However I do share your strong desire to heat DHW with wood.

Has anyone tired to cobble together some kind of heat pump system for DHW that uses the hot air in a wood stove heated basement to heat the hot water? If the equipment were inexpensive enough and quiet enough, I'm sure I have enough heat in the basement (80+ deg) to heat water. It would save half of the 400 gals of oil I use on DWH each year (could only use it in the winter). Not sure if this makes any sense so please let me know your collective thoughts.

 

[Eric Johnson]

and what about a release valve

And what about an expansion tank? You don't want to heat water without a couple of places for it to go if it overheats. Isolation valves, a flow control valve, vents and drains--these are all essential items. You might need an expansion tank, and maybe even an air scoop. It all adds up, and most of it is essential for safe operation. The $200 heat exchanger is only one part of a larger undertaking.

 

[webbie]

Still ends up being a lot cheaper than Solar and some other DHW helpers. I doubt many new stove owners are going to be getting the drill and the torch out, but these things are a good option with "total" systems that include solar panels, a tank and a woodstove, etc....Probably useful for a lot of Furnace installs since these are in the basement (maybe close to the DHW) and also this keeps all the plumbing in a place where you don't have to worry about the PR popping onto the new white carpet.

 

[begreen]

You might want to try and contact John Gulland. It can be done, but would be foolish to try without proper safety systems and a thorough knowledge of what needs to be watched and what can go wrong. The folks in the boiler room would be more appropriate to talk to for available parts and controls.

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

domestic solar hot water:
http://www.gulland.ca/homenergy/solardhw.htm

 

[steam man]

I have read a number of threads on installing water coils in a wood stove application. I have been doing this set up for a year and a half and it works pretty good. Actually, I plan on installing a wood boiler and solar collector system eventually with a sophisticated control setup. I have most of that equipment. However, I am finding using the setup with an (not sold anymore)Eagle wood stove and the external stainless plate heat exchangers for its simplicity makes it hard to justify the expense and complexity of anything else. I've used the stove for 18 years and have never had creosote or much soot to speak of. The Maine guy (friend of mine) with the Black Bear boiler and tank farm gave me the plate exchangers. The 120 gallon solar tank was acquired new as a "throw in" along with another deal. The storage is located about 40ft away so I use a Taco 006 bronze pump and a solar/wood stove differential controller to run the show. I can heat only the 120 gallon tank or loop through the 40 gallon indirect tank (which I can remove from the primary boiler loop) for 160 gallons of storage. I typically will only get the storage up to 115F before much hot water use. Plenty for showers and baths. I can flip a switch to have the 40g tank fire up from the boiler. I have debated installing one or both of the exchangers in the secondary chamber of the stove. That may mean some kind of loop return temperature control along with the disadvantage of possible creosote formation and power outages. I do have a small radiant loop that can be connected to take the surplus heat generated if I go that route. I have fired the crap out of the current setup with the pump off and cannot seem to create any overheating problem. However, not enough heat is generated for my radient loop. I do have multiple relief valves, expansion tanks, and a method of flowing water through in the event of a power outage. One problem others have talked about is the possibilty of soldered joints blowing out on overheating. I added some stainless pipe extensions to clear the wood stove by at least 8". I noted others would like to make a copper coil for the same application. I would suggest thinking about making a stainless coil and using Swagelock compression fittings. I can't see the disadvantage. This stove burns green wood which is a plus for me (plus the wife can run it). I have debated the pros/cons of installing a wood boiler and the jury is still out. Being an engineer I probably will do it because I can. The solar panels are going up this year after I redo the roof shingles.

 

[oldAGE]

Steam Man - That's just awesome. Do you think a larger fabricated stainless exchanger would add greater value? It seems that there is 1/3 the surface area that is being lost. But, I guess you couldn't beat the price! This is a thing of beauty!

AGE

 

[steam man]

oldage-your post couldn't have had better timing since my wife was sitting beside me when it popped up. She thinks we're all nuts. Those plate exchangers were manufactured years ago by but I don't think they are available now. They are solid stainless with drilled passages and a welded on manifold end. They are designed to go into a firebox. It would take a lot to make them fail. My stove could handle more of them on the surface since it burns really hot. I am not anywhere near dragging the stove down. Like I mentioned before-I am considering trying putting one at a time in the secondary chamber. My next step is to maybe put a shroud and some insulation on top of them just to see if it helps. I could also insulate the lines. I figure I just lose the heat to the house so I don't mind. Actually, you gave me an idea where I could run some tubing on the back of the stove and then to the plates for more surface area. I do think I have a pretty good balance between space heat and domestic water though I will probably end up pushing the envelope a little more. In the last month I used about <1 gallon a day of fuel oil for what you see pictured.

 

[oldAGE]

Of course we are crazy... we're men! Only wish I had the time and talent. By the way, the picture looks like what we looked like a month ago... I wish I could say the same thing about my furnace. Unfortunately, I have been fighting an over fire and misbehaving woodstove for the past month. I hope to have it licked by this weekend... just in time to go from 10 below to 25... Grrrrrrrrr!

AGE

 

[steam man]

Heck-my wife will admit to being responsible for making me crazy. Take a look at this link: http://www.yukon-eagle.com/Portals/0/manuals/Hot%20Rod%20Manual%20(Revised).pdf. Looks like it might work OK embedded in the coals with a gravity loop, especially for Shortwave's scenerio.

 

[TreeCo]

The Hilkoil coils look to put more surface area inside the wood stove compared to the Yukon-Eagle Hot rod. I like the idea of it being bent tubing Vs. being welded.

 

[atog254]

My father got me into burning wood as a kid and he had a SS dough-nut that fit around the flue pipe as it left the wood-stove. Heated our hot water for years. And when we built this house in 1988, I did the same. Only went a little further and have a wood furnace. The SS dough-nut is on top of the furnace and is copper piped to our water heater and is covered by pipe insulation. Have a temperature pop-off valve just in case of over heating. When the water heater was installed, it had to be raised off the floor to permit the natural circulation (Hot water rises!) My system has not failed me, however I have had to replace the water heater twice in 22 years due to it leaking! As far a build up of creasote, I've not noticed that to be a problem and clean my chimney EVERY year! I do not know if these water jackets are still available, but if you have a good welder that can work stainless steel, I sure one can be fabricated!

Good Luck, and go for it!

Stove vs Steve

 

[Techstuf]

How about a hot water heater with insulation removed from one side, standing at the right proximity to a wood stove. The side facing the stove is single walled and painted black. A compensatory insulation blanket could easily be fashioned. Remove the jacket in winter months and the blackened metal absorbs radiant heat, transferring it directly to the water inside, never allowing it to reach boiling point via a reflective heat shield that rotates via thermostat, partially eclipsing the radiation, in order to maintain water at the desired temp. Or by placing the heater at sufficient distance to preclude such danger at all, merely augmenting the heater's normal heating method. Warm days or when fire burns down, and the native water heating system kicks in as normal. A simple wood stove assisted water heater which automatically takes over when the stove is at operating temperature. No steam, less danger. In warmer months, replace the jacket and heat via the heater's normal requirements.

Of course, I'm thinking like a basement stove owner, which I am.


TS

 

[brokeburner]

My father got me into burning wood as a kid and he had a SS dough-nut that fit around the flue pipe as it left the wood-stove. Heated our hot water for years. And when we built this house in 1988, I did the same. Only went a little further and have a wood furnace. The SS dough-nut is on top of the furnace and is copper piped to our water heater and is covered by pipe insulation. Have a temperature pop-off valve just in case of over heating. When the water heater was installed, it had to be raised off the floor to permit the natural circulation (Hot water rises!) My system has not failed me, however I have had to replace the water heater twice in 22 years due to it leaking! As far a build up of creasote, I've not noticed that to be a problem and clean my chimney EVERY year! I do not know if these water jackets are still available, but if you have a good welder that can work stainless steel, I sure one can be fabricated!

Good Luck, and go for it!

Stove vs Steve

can u post a pic of that stainless donut deal love to fab on or two up

 

[peakbagger]

A friend down in southern maine uses a hot water heater tank from a hot water heater painted black right next to his wood stove to preheat his domestic hot water. He also has a bunch of short sections of fin tube from a baseboard soldered up into a rectangle that sits on top of his wood stove. He heats with wood with a oil furnace availlable but not connected as he has only one flue pipe. If his zones are calling for heat, the circulator pump on the boiler runs like a normal oil boiler. He has a backup aquastat on the coil that turns on the circulator and runs it to a dump zone in his basement until the temp in the coil drops if it exceeds a certain temp. The relief valve on the oil boiler protects from overpressurization. If he loses power he has valves and unions set up so he can remove the coil and run the woodstove normally. He even has enough hot water off the hot water tank to take a shower (he is on city water so no need for a pump). He has heated with wood during the winter for close to 20 years with really no backup except when he goes out of town. The oil boiler is for spring and fall when its cooll in the morning but warms up during the day.The coil on top of his wood stive has cut his wood usage down by about 1/3 as he doesnt have to overheat the basement to keep the upstairs warm. I keep working on him to install a wood boiler in place of his fisher to cut down on his wodo use but he happy with his system.

 

[Techstuf]

Checked 'em out on Ebay......


http://myworld.ebay.com/thermo-bilt/


Interesting product, might have to give it a go.



TS

 

[Wet1]

I've been toying with doing some type of preheating of the DHW with my stove. I'm not crazy about the idea of drilling any holes in the firebox, but plate heat exchanger(s) sounds like it might work well for what I'd like to do. More thoughts and options are certainly welcome.

 

[atog254]

My wife reminded me that when my dad passed away, my mother stopped using the wood-stove and my brother and I removed it from her house. The stove was sold, but i think I still have the SS water jacket.

If interested, I will look for it. This is like mine and works great. Just remove the flue and place the jacket behind or atop the stove and reinsert the flue. Pipe with 3/4 copper with temp. and pressure relief valves. Have not see this is quite some time, but again, if interested, I will search my storage barn for it.

Stove vs Steve

 

[awoodman]

No one has asked the question of condensation driping off the coil inside the fire box. This time of year the ground water is really cold so how can this not hapen?

 

[Andre B.]

Back some time in the 70's my dad put a homemade one in an Andrews wood burning furnace.
He just used some hardware store black iron fittings, 2 elbows a short nipple and 2 short lengths of pipe inside the stove. Put it in just above the fire brick, in use a layer of fine ash would cover it up so it was protected from the most intense heat, lasted about 15 years.
I would not get all that exited about paying that much for a ready made stainless one.

He had it connected up to a 40 gallon tank with a 10 gallon expansion tank in the floor joists, the heated water then went to the regular propane fire water heater.
A side effect of the system was that in cold weather the preheat tank temperature could be higher than the propane heater was set for so the hot water temperature at the sink would go up when you used up the 40 gallons in the propane heater.

With my more modern EPA stove I would just put a loop inside the heat shield outside the fire box. But then I a single and do not use a washing machine at home in the winter and so do not need much hot water.

 

[kenny chaos]

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