Woodstove Water heating - Anyone seen/tried the Therma-Coil?

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My initial thought is that by modifying a woodstove you will alter it's characteristics.
By heating water inside a stove that was not specifically designed for this may well cause the stove to run cool, and at worst may well cause problems with the flow of gases inside the firebox and cause problems with secondary burns or cats.

I'm interested in other people's thoughts on this, and any experiences.

And neversummer, welcome to the forum :)
 
There just isn't enough space in fireboxes for those things. It is hard enough to stuff enough wood in most stoves for a long burn without losing space to water heating coils. Or worse yet having to worry about damaging the things with the splits. And from there, like the man said, you are robbing heat from the burn. These things would be better used in a cheap stove dedicated to hot water and smoke production.
 
Couple of other thoughts......

No thought is given in the sales pitch that many woodstoves are made out of cast iron, not sure if i would be happy at punching holes through the side of a cast iron woodstove.

And the installation into the tank seems to be basic for just plumbing the woodstove in. I would have thought more complex plumbing would be needed to fit up as an addition to a solar system which is what it is implied to complement in the advert. After all, when the woodstove is not heating the water, what is stopping the water from cooling down by still circulating water as it is an unpumped gravity system.
 
My thoughts exactly, and a quick call to Woodstock Woodstoves last week resulted in the same response "I don't know if I'd do that". Seems like something of this nature hasn't been done although I've read alot of people -talking- about placing some type of tubing on the back of their stoves to get some radiant heat into their water as a jump start to the oil. My guess is not many have actually attempted it.

I may, once I have the stove installed, do a bit of a science experiment this summer. Take two 5gal buckets, one on each side of the stove. Try heating the water by placing the pipes on the back of the stove or as close to it as possible. Pump cold water from the full 5gal bucket on one side through the mock-up heater and into the empty 5 gal on the other side. Measure the temperature change using a few different construction techniques, and we can finally put to rest whether the heat gained by the water is worth the effort.
 
I'd avoid having buckets of water next to a hot stove. If the water gets knocked over onto a hot stove, you could crack a very expensive stove.

Now, if you want to get something extra out of your woodstove, use it for cooking (only easy if it's a flat top like mine).

Cooking uses a lot of power, and there is something really cosy about having a casserole cooking quietly on the flat top of a stove.

Plenty of threads on here from people who have cooked on their stoves (and some tasty pizzas done inside) :)
 
neversummer
I installed one of those coils in my steel stove, July 1983. The coil is still in the stove to this day, has not been used for 20 plus years. At the time I used an old oil boiler with a tankless coil as storage to pre-heat incoming water for my electric water heater. The results at best were less than fantastic, and I felt contributed to poor burning characteristics, as the coil was cooling exhaust gases at the same spot todays secondary burn tubes would be heating. Interestingly enough illustration stove looks exactly like mine, and if I get inspired this summer the coil is coming out and the existing holes will be utilized for a secondary burn experiment.
 
In certain instances, these can work out. I wrote an article on them in our articles section.....

In a general sense, I used to like putting them on the OUTSIDE of the stove in the rear....not as quick to overheat. Ideally they should be installed fail safe with a storage tank and a rise to the tank.

I'd say they are not for everyone...in any case! But they make a nice add-on to certain stoves when tied to solar hot water, etc......
 
I used a Hilkoil about 20 years ago in a add-on furnace, Clayton was the name. It had the holes pre-drilled and the coil was up against the inside wall out of the way. If I remember correctly no circulator pump was needed if your hot water tank was 10' or less, which mine was. A new pop off valve came with it.
It would heat all of my hot water and I had 4 in the house at the time. It definitely worked as advertised.

Gary
 
We used to sell a unit called the Hydo-Coil, but it would void the manufacturers warranty drilling holes in the side of the stove, cut down on the space for wood, and cool the air going up the chimney which would cause more creosote. It would also mess with any EPA stoves designs for clean burning by cooling the gases in the firebox.
 
Yes, we had one installed in a Charmaster wood furnace and it worked quite well...but it was plumbed into a secondary water heater that supplied the main water heater. The complete setup was in close proximity and the water was tempered ...don't think it would alleviate your need for a water heater completly.
 
I have one on modified ( secondary air tubes) Fisher stove in the basement. I can easily heat 100 gl of H2o to 180 °F .
Here is something I posted earlier. I am at work now so I don't have any pics handy.

Some thoughts on water heating. I have a Fisher stove in the basement set up to heat DHW.
It works quite well. Right now I have 100gl of H2o at 160* in the tank I heated last night.

First, I would not use a modern EPA approved for heating DHW, my Fisher is an older stove that came with the house.( it is modified with a baffle and secondary air)

Also I don’t think stove heating DHW should be in a living area, I would not want to have that in my living room.

My stove has 2 external heat exchangers on the side and top and an internal U tube heat exchanger inside the firebox. I have estimated that I can extract 16,000 btu/hr.

My system is an open/ non pressurized system, the water is circulated by a pump from 2 55 gal drums connected together. Also I have 2 pressure/ temperature relief valves, I think this is a good way to go for safety.

Each drum has 200’ of pex tubing acting as a heat exchanger, Cold potable water travels through the pex and then into the electric hot water heater.

I burn mostly pallet wood in the Fisher, it burns nice and hot. I have no problem maintaining a good flue temp. I cleaned the chimney around Christmas and there was hardly any creosote.
 
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