Adding a Water Heater Coil

[newguy08]

I am thinking about adding a water heater coil to my wood stove. Has anyone had any luck? What type of stove do you have? Thanks!

 

[kenny chaos]

Hello NY!
I don't know if you'll get many replies.
This has been discussed an awful lot.
Have you done any searches of the forum?


What kind of stove do you wish to use?
What kind of coil/coils?
How much water are you wanting to heat?

 

[Dune]

I added a coil to my steel stove. (Tempwood)

 

[kenny chaos]

I added a coil to my steel stove. (Tempwood)

What kinda coil and what ya gettin' out of it?

 

[Rebel Wood]

I added a water coil to a Hutch Rebel, Fisher clone, years ago with disappointing low output. Also contributed to creosoting, as the cold water was at the worst possible spot in the stove. Coil is now coming out to pursue baffle, secondary burn tube, as explored in other existing posts.

 

[Jimbob]

I am thinking about adding a water heater coil to my wood stove!

http://yukon-eagle.com/hotrod.htm

(broken link removed)

 

[Dune]

I added a coil to my steel stove. (Tempwood)

What kinda coil and what ya gettin' out of it?

I drilled 6 holes on each end of the stove, then slid six sections of 1" shed. 40 steel pipe through, and conncted them with weld 90s. The top and bottom pipe are threaded, and on the top pipe, I installed and aquastat well and a radiator coin vent. The aquastat is connected to a dedicated taco 007 circ, that runs continuously as soon as the water temp hits 160f. It is then tied in parralel to my existing hot water heat, with an extra check valve, expansion tank, and pressure relief. Have not run the oil burner yet this year. Do not have a dump zone or storage, but I do have enough materials to install a zone of radiant heat in the two bedrooms and one bathroom which are farthest from the stove. When I complete that job, I will then add a storage tank. The dump zone is not needed, if too hot, damp down the stove, open a window, or whatever, just like heating with a stove. I had planned to hook it up in series, but NoFossil from the boiler room convinced me otherwise, for which I am profoundly grateful, as I do not need the oil burner anyhow, and it would have acted as an outdoor radiator. It is available if I had to leave town for a few days or whatever, but I keep it shut off.

 

[mnowaczyk]

Nice work Dunebilly! Sounds impressive.... and like a lot of work, right? Are you for hire?

I too am interested in the concept of heating water with my stove. I've got oil radiator heat (old furnace), an old 75 gallon rusting gas water heater ($60 per month in gas charges for my only gas appliance). My oil heater and gas water heater shimney runs right next to my fireplace chimney, and I will be installing a chimney liner for my wood stove. I might as well do the heater chimney whil at it. So I'm prime for some updates. I'm looking at a tankless water heater this time around. I was also thinking about getting rid of the oil for my radiator heat and using natural gas.

I was really starting to think heating water with the wood stove could make sense... that was before I started thinking about creosote. Add to that the complexity and the potentially minumal cost savings. Is best-of-breed a smart way to go? Wood stove will provide quick, primary heat for house, immesely off-setting my oil costs... so why upadate the oil heater if not needed? And use Tankless gas for hot water to the house. (Or maybe for those of you afraid of loosing power, you'll stick with your tank water heater, huh?)

Keep it simple?

 

[karl]

I'm going to do something to heat my water as a summer project. Solar is a real possibilty.

As for the stove. I'm thinking about putting a water coil on the outside of it. I have an insert and I could attach it to the back of the stove and keep it out of sight.

I don't think it will pull so much heat away from the stove to hurt burn performance. From looking at my gas bill I only need 33,000 btus a day to heat my water. That's 1375 buts an hour, I need to pull from the stove. So I think I can do it with an external coil. Plus I plan to add insulation around the water heater to reduce that number a bit.

 

[mnowaczyk]

Karl:

I have to admit I was thinking along the same lines. Put a water coil behind the insert in the fireplace coming up through the ash cleanout. Is that what you are thinking? It sounds very simple, to at least give a little pre-heat to the water heater. What size coil are you thinking?

And oh... don't forget to add some type of circulating system... Right? And what? A storage tank too? That complicates the project. If you don't ahve any circulation, you are only heating the water that sits in the coil. The minute you turn on the hot water, cold water will rush into the fireplace, and run through too quickly to be heated. Right? Only the new technology of a tankless water heater can handle this type of flow. Right?

 

[johnn]

Karl:

I have to admit I was thinking along the same lines. Put a water coil behind the insert in the fireplace coming up through the ash cleanout. Is that what you are thinking? It sounds very simple, to at least give a little pre-heat to the water heater. What size coil are you thinking?

I too, am interested in what you are doing, so refresh the thread from time to time so, I can follow and learn. Not being able to fully understand what I read from the boiler room,,it takes many visits and lots of reading and lots,lots of time ,but I do learn a little with each visit. Perhaps if you could post a diagram of your current piping and what you would like to do,,they may better help.I have been considering a add on wood burner for the furnace, utilizing the domestic water option available. Being interested in tankless hot water, I would have storage to operate some baseboard heating from the existing hot water tank??

I also have an insert sitting on top of my louvered ash dump,which empties downstairs,,,above the mantel downstairs is the access door. I would like to hard duct a blower downstairs to the louvered duct upstairs,,,elevate the insert,and remove the top sourround panel in order to force that trapped heat into the room(I`m sure I would have to block off some of the voids in order to have air pressure) Good luck

 

[begreen]

I drilled 6 holes on each end of the stove, then slid six sections of 1" shed. 40 steel pipe through, and conncted them with weld 90s. The top and bottom pipe are threaded, and on the top pipe, I installed and aquastat well and a radiator coin vent. The aquastat is connected to a dedicated taco 007 circ, that runs continuously as soon as the water temp hits 160f. It is then tied in parralel to my existing hot water heat, with an extra check valve, expansion tank, and pressure relief. Have not run the oil burner yet this year. Do not have a dump zone or storage, but I do have enough materials to install a zone of radiant heat in the two bedrooms and one bathroom which are farthest from the stove. When I complete that job, I will then add a storage tank. The dump zone is not needed, if too hot, damp down the stove, open a window, or whatever, just like heating with a stove.

I think the dump zone is more of a safety feature. What happens if the power goes out and the circulator pump doesn't run?

 

[karl]

I haven't gotten much past the brain storming part of it. I know it's doable. My humidifer sits on the heat shield portion of the stove and it gets to 150 degrees easily. I may space the pipe away from the stove to avoid boiling the water.

Brazing would be the easiest but is probably won't take the temperature. I need to research it more.

I want to stay away from stainless steel if I connect it directly to the stove. Certain stainless alloys will leaeh chromium at around 1000 degrees.

Surface area is key so I'm leaning towards a mild steel square tube. This could be welded to the stove as well. I need to research heat transfer per square inch at certain temperatures. This will tell me for sure weather or not I actually have the tubing in contact with the stove. I'm really leaning against it. I've seen a post or two in thread that could be dangerous. You dont want to have the boil. If the tubing gets over 212 then the water will boil unless your constantly using it or have a storage tank that will asborb the heat until you use it. Here's my plan.

Take the drain out of my current water heater and attach the tubing there. Then take the pressure relief valve off the water heater and install a T. One side of the T will have the pressure relief valve and the other will go to the stove. Now I have an inlet and an outlet to the water heater. My water heater is in the basement and the stove is on the main floor so I will need a pump, but not a big one. We're not moving alot of water here and since it returns to the same place, there is essentially no head involved. I would need a temperature sensor to turn the pump on and off. That's a pretty simple circuit to build, but it should have hysterious built into it. Then run the water up to the stove and through the manifold I'm going to build.

I have a 50 gallon tank and I live alone, so I don't go through alot of water. I'm trying to get rid of natural gas, so I may add a small tankless electric to take up any slack.

I do have an ash clean clean out that is now provides my outside air. I can run the tubing through it to the basement pretty easily.

Any input would be appreciated.

 

[johnn]

Karl: How does the tankless system plumb in so that it becomes the secondary supply, rather than the primary?

 

[karl]

Here's a quick drawing. The blue is square tubing. The angles could be cut on a miter saw with an abrasive blade. The welding would be a bit fiddley but not difficult. The red is a piece of plate steal. You could use copper tubing to brazed to the plate steal too. I would flatten the tubing a bit on the steal.

Then place the thing about a half inch away from the stove. The steel will catch the heat and let is soak into the tubing.

Like I said before, I only 1375 btus an hour and that's assuming the water heater is 100% effecient. I'm thinking its maybe 80% so I need 1100.

 

[newguy08]

Everyone has had some great information. There is an ad on EBay for an add-on system like you have described. http://cgi.ebay.com/Hotwater-Wood-Coal-Stove-Add-On-Boiler-Watertank_W0QQitemZ120382839215QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item120382839215&_trksid=p3286.c0.m14&_trkparms=72:1205|66:2|65:12|39:1|240:1318|301:0|293:2|294:50

 

[Dune]

I drilled 6 holes on each end of the stove, then slid six sections of 1" shed. 40 steel pipe through, and conncted them with weld 90s. The top and bottom pipe are threaded, and on the top pipe, I installed and aquastat well and a radiator coin vent. The aquastat is connected to a dedicated taco 007 circ, that runs continuously as soon as the water temp hits 160f. It is then tied in parralel to my existing hot water heat, with an extra check valve, expansion tank, and pressure relief. Have not run the oil burner yet this year. Do not have a dump zone or storage, but I do have enough materials to install a zone of radiant heat in the two bedrooms and one bathroom which are farthest from the stove. When I complete that job, I will then add a storage tank. The dump zone is not needed, if too hot, damp down the stove, open a window, or whatever, just like heating with a stove.

I think the dump zone is more of a safety feature. What happens if the power goes out and the circulator pump doesn't run?

In the event of powerloss to the circulator, the temp/pressure releif will bypass untill all the steam/water escapes.