Wood stove heat exchanger

Chris Janowski

I have a wood stove that I would like to link into my hot water radiant system.
Any body have any experience fabricating a heat exchanger to install in a wood stove? I'm thinking copper, and silver solder welds.

Any slick ideas for turning on circ pump automaticly when the wood stove gets warm enough? (I have Munckin 80m)
Seems like I would want a pressure relief valve in the system-near the stove?

Am I missing anything?

Constantin

Several options...

I'd go with a flat-plate HX since they're cheap and get the job done.

However, I'd think VERY carefully how to do wood boilers inside a home. For instance, a LWCO works quite well to stop a regular boiler when the boiler goes low on water. However, a wood fire has a tendency to keep burning and can flash to steam with a nasty surprise.

This is one of the reasons I suspect many wood-based boilers are housed in external huts. Seeing a boiler take off from there is relatively benign compared to sitting above or next to it when it decides to explode.

So think carefully about sooting issues (Creosote) and boiler issues before hooking up something home-made. I suspect that a EnergyStar-compliant stove is likely to be a better investment and safer to boot. This is not to say that what you seek cannot be done, I just question whether it'll turn out to be cost effective.

hr

Be careful

you need to have protection should the flow be interuped, power outage, etc. A properly sized relief with the discharge to a safe location.

Consider putting a HX on the backside of the stove outside the firebox. I have built several over the years with 1" sch 40 pipe and fastened them to the stoves.

hot rod

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Brad_9

Copper piping is OK outside of the fire box, but NOT inside. It will corrode fairly quickly and do a very good job of putting out the fire.

Bob Gagnon plumbing and heating

bigger heat exchanger

I was going to do what you are thinking of, but now I'm going to wait and install radiant ceilings and walls near my wood stove. I think that will help move the heat near my stove to the other parts of the house. Bob

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jerry scharf_2

interest3ed to hear the results

Bob,

I would love to hear how this turns out. I hope you can put some data logging thermometers around and measure how it works. I have some thoughts that could help in that area if you need it.

jerry

Jack_21

I built one yrs ago

for my Dad. He was retired, home most of the time and knew what he was doing with a wood fire. I basically made it out of plate steel and made the back wall into a water jacket. When ever he built a fire he turned on the pump. I used 3 PRV's (you cannot be to careful on this). the following year we built a sheet metal cabinet over it and ran a large duct up to the hallway on the first floor. System worked great...but again, Dad paid attention.

Bob Gagnon plumbing and heating

Jerry, help needed

I'm running 80 - 120 degree solar heated water through my radiant system, with extruded aluminum plates in close proximity to the wood stove. it should move the heat to the other rooms, right? Your thoughts on this would be appreciated.

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Mark Eatherton1

Bomb in a box...

Theres a housing project just south of Denver that had all solar and heat exchangers inside of wood burning stoves. There was NO back up to these systems. Not sure how they snuck that detail past the bankers, but anyway, they had these stainless steel thingambob heat exchangers (Colmac Coils) in the fire boxes of all the stoves. I personally saw one that had boiled out and when the solder joint below the floor failed, it imbedded the 3/4 type K copper line into the solid wood floor joist to the point that it could not be removed. I'm not trying to discourage anyone... Wait a minute, YES I AM, Don't do it. It is extremely unsafe unless you have some guaranteed way of maintaining flow during a power failure.

I had a copper external one on a wood stove in my 2nd house. It had a manual control (ME) that turned the pump on and off to circulate water betwixt the heat exchanger and the DHW preheat storage tank in a room about 30 feet away. One night, I'd started a good hot fire in the stove, and forget to turn on the switch. My eldest daughter (5 years old) was in the basement with me, and came up to me and said "Daddy, how come the stove sounds like mamas tea kettle?" I wheeled around, and grabbed her, and just as I hit the door, the coil cut loose on a red hot stove, and we were literally blown into the other room by the force of the steam blast, A.O.T.K.

Never again. I disconnected it and have not experimeted with that kind of power since.

External (outside the home) wood burning stoves are non pressurized vessels for a reason...

Proceed with extreme caution.

ME