Adding water heating to woodstove

[weldingrodd]

Looking for a forums to go to and also any comments from anyone who has added water heating by way of a copper coil or U shaped iron pipe mounted in or on outside of firebox of woodstove .Would like thermo syphon method if possible but could use a pump. Would like to add a couple hotwater baseboard units to an unheated area.

Any thoughts would be appreciated

[picmacmillan]

hello not sure if this will help but when we go moose hunting we have a stainless steel tank similar to a gas tank, attached to the back of the wood stove. this obviously gives us hot water all the time and it puts some moisture back into the air so the air isn't so dry as is usuall with wood heat. I hav also seen copper pipe wound around the woodstove pipe and up nto the attic, not sure how far it goes past that, but it would be easy to figure out how much volume of water would be available and again it would always be hot. i found the copper wire thing wasn't too pleasing to the eyes but their was always lots of FREE hot water....take care...pickster

[JW]

There is a very economical circulation pump available in the McMasterCarr catolog. It runs on like 12volts at 3amps. It is the type with a magnetic power coupling(instead of a lovejoy coupling)And has a brass housing for the impeller. I think its rated to like 100psi, and 4gpm thru 1/2 npt couplings for circulation, please bear in mind this pump is cyntrifical not positive displacement, good for circulation only. But can handle 15psia operating pressures. I think it costs 230.00 usd. Would work fabulious for circulation from your primative heatexchanger(on wood stove) to your holding tank with safety valve(temp or pressure activation) then you could use more pumps simular, at 4gpm to recirculate fluid from base board heatexchangers back to the main tank. It would be a true "hydronic heating system" probably be best off operating the main tank at 180*f or less(fuel stoking could vary to maintain this temp). Solid fuel burners do not shut down as convienently as fuel oil burners, the safety valve on a conventional water heater should provide some protection in the event of overheat, should the primary heatexchanger on the wood stove be in communication with this resivior and main safety valve (lift-check type safety valve would be nice). In theory any branch of circulation to floor base board heaterexchangers would be protected by this atmospheric control on the main tank. Just be sure the safety valve vents outside or in a safe place, you very well may finding yourself using much less wood. The system will recycle alot of the heat if the storage tank has any capacity.

 JW

[hiker]

before are gas furnace was hooked up--the baseboards were installed on the second floor..and we heated the house with a barrel stove..any way the second floor was allways kind of cold so my dad put a copper coil in the back of the barrel stove and hooked it up to the pipes going to the upstair baseboards--had great heat after that.

im not sure if he used a pump or not[little rug rat back then]..old enough to chop all the wood thou :]..............

[marv]

http://www.otherpower.com/images/scimages/678/hot_water_system.GIF

[Ungrounded Lightning Rod]

I note that if your heat consumption is a few feet above the stove (like a hot water storage tank or baseboard radiators on the second floor), convection should be adequate to drive the water circulation, so a pump (and its associated power supply) should not be needed.  You just need to route the pipes so the water has a preferred circulation direction and no vertical doubling-back to impeed the start of convecton.

In fact, if you plan to heat both the second floor and the first floor with baseboard radiators, I believe convection will still do the job adequately - first driving the hot water up to the second floor, then returning the warm water for a pass around the bottom of the first floor before it again passes through the fireplace heater.  (The second floor will necessarily receive hotter water so you'll want short baseboard radiators there, longer ones on the first floor, to even out the heating.)

Regardless of whether you're using it for water supply heating or driving a radiator system, you'll need some kind of expansion tank to absorb the water expansion when the water heats up, and a pressure relief valve to prevent pipe breakage and floods - or explosions - if the expansion exceeds the limit (i.e. if the tank becomes waterlogged).

In a water supply heating situation the pump pressure tank or the incoming water plumbing might serve as the expansion tank (though you still need the relief valve - in case there's a blockage, a check valve, or someone turns off a supply valve and the pressure limit is exceeded).  For a recirculating system you'll want to put in an explicit tank - with an air bubble and top and bottom valves for restoring the bubble, or a bladder (if you can find one rated for the temperature).  Of course the tank should be at the top of the system (so any air ends up in the tank, not blocking convection.)  The relief valve can be at any height in the plumbing - though lower is better so it releases water, not air - and you should put the discharge end somewhere where a few gallons of (boiling) water won't damage anything (because it WILL operate at least once during the system lifetime.  B-) )

[weldingrodd]

I made the heat exchanger for my system from 1 " black iron pipe serpentined with 90% elbows and 90% street elbows which made a much tighter bend than I could done trying to bend the pipe. I will about 5 feet of 1 " pipe inside firebox with bottom section of pipe being in hottest area. Would like to have the convenience relying totally on convection. But maybe I would be better off using my old 40 gallon water heater as a storage tank for the water and then maybe use a ciculating pump to move the water through baseboard exchangers?.Like idea of no pumps or electrical gear involved though but am a apprehensive as to what might happen if it sprang a leak? I guess the pressure/temp valve would take over and system would steam away the water and be ok till leak was fixed....I am toying with idea of venting overflow or safety valve directly into my main 3 inch sewer pipe ..Hoping that if it did boil out the water it would go down the pipe and be outside. I have heard of a person venting his overflow into 1.5 inch PVC pipe and water was so hot it actually sagged the piping to the main line!

Any thoughts and comments greatly appreciated. I have access to welders and metal cutting tools ..If you feel my exchanger pipe is too long or too short please let me know...The 5 footer I made only cost $28.00 and no work involved other than taping joints and wrenching them together.

Also I have to route pipes about 15 feet to entry then upward to kichen floor Room is 16x24 I think.I was thinking 2 or 3 8' sections of baseboard although LOWES had a "Kickboard" heater with fan for hotwater for $130 1/2 price with a small fan and 2 exchagers inside about the size of a good size car heater core...If I used a pump I could keep exposed piping to a minimum with a pump....cant elbow up and down and up again with convection can you? weldingrodd....add @  and hotmail

[Vtbsr]

There is a lot of water heating info on www.houseneeds.com

[robl]

Black pipe is the way I went. I just cut and threaded two one-foot lengths, used elbows and very short nipples to connect the straight lengths, and 3/4" hydraulic hose to connect the inlet and outlet to the exterior 3/4" piping. Used both a pressure/relief and a vacuum valve to protect the system. Used a 40 gallon electric hot water tank for the storage portion (about 8 feet above the stove, but on another floor would have worked as well). Thermosysphons no problem. Don't forget a drain tee on the lower (cold) section of the coil to avoid corrosion and freezing problems. We use the system for domestic hot water and it has been working this way for almost 20 years. I did have to put in a new tank after the first one sprung a leak and now have to replace the black pipe because of corrosion. The new pipe will be stainless (from a junk yard) as I discovered something was a actually "growing" inside the black steel pipe that was restricting the flow. Still, 20 years ain't bad.

Regards

Rob