Wood cook stove/hydro boiler combo

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

Bk-crow

New Member
Aug 7, 2022
4
BC Canada
Tl;dr is the ABC Concept 2 Wood cook stove/hydro combo a good product that can actually heat a whole house with hydronic system, domestic hot water, and cook food, or is this way too good to be true and won’t be enough? Possibly some more in depth questions for the boiler room forum later, but right now just asking about a specific wood stove option.


Hello, we’re planning a new off-grid house build, and trying to make some decisions on our future heating system.

We had hopes originally of incorporating in floor hydronic heating into the design, running off of a large wood-burning boiler in an attached garage. We also really want a wood burning cook stove in the kitchen for winter cooking and supplemental heat.

The engineer we’re working with to design the house pointed out some of the European wood cook stoves available at Obadiah’s that have boiler functionality built in, and could theoretically be connected to a hydronic heating system. Specifically the “ABC Concept 2 Hydro Wood Fired Oven with Boiler” may be big enough to meet our needs.

The house will be about 1500 sq ft, 900 first floor and 600 upper. We’re still working on the heating budget and r-values, but he estimated we’ll need a heat source that puts out a minimum of 65,000 btu. This product claims to transfer about 72,000 btu to water and over 13,000 to air.

There will eventually be a garage/shop built on, several years after, but at this point we’re just looking at something that will heat the house we will live in initially. We are attracted to hydronic concept to spread heat around evenly through the house, rather than having a hot kitchen and cold bedrooms.

For context we currently live in an owner built straw bale house that has some serious type one errors, the foundation is bad and the house is slowing sliding downhill toward a creek. We have a basement in this house with a big blaze king that heats pretty well, and a little stove in a side bedroom. We generate our own power through micro-hydro and solar. Our house is often cold in the winter, drafty and heats unevenly. We now have a much bigger budget and are investing in a professionally built, well insulted and designed home. No basement in the new house.

Anyway I have serious doubts that this product would actually be what we need. The salesperson at Obadiah’s was very positive about the concept, but it still seems wild to me that a cook stove with a small firebox could also be heating water that runs through a whole house, and do any of these things effectively. Makes me a bit nervous having this complex and potentially dangerous system that requires electric pumps to even use the stove at all.

Our structural engineer is not a heating/plumbing expert. Obviously we would hire and consult with professional hydronic heating and plumbing experts for installation when the time comes.

It’s just the idea of having only one wood stove in the house that does it all is very attractive. I guess my question is, does anyone run this kind of system, hydronic whole house heating/domestic hot water off of a coil in a small indoor wood stove, does it work efficiently? Or should we just rule out this idea?

I’m personally thinking we should keep it simple and just start with a big Amish cook stove in the house initially that throws out a lot of heat, like a Kitchen Queen or Heco. Run PEX line in the floor in the initial build, but install a standard wood boiler along with the shop build several years down the road.

Anyway curious about the experiences and opinions of others. I’d rather seem ignorant on the internet and figure out what we really want before we go to the professionals.

Thank you!
 

EatenByLimestone

Super Moderator
Staff member
They don’t mention the firebox size.

The stove may be able to put out the required btus, but for how long? You said it has a small firebox. Does this mean you’re going to be loading it every 2 hours? That’d get old fast.
 

EatenByLimestone

Super Moderator
Staff member
Are you sure the heat loss calcs are correct? Those are very high numbers for a modern house that size. Is it made of glass? I’d expect a modern, well insulated house to need half of those numbers.
 

Bk-crow

New Member
Aug 7, 2022
4
BC Canada
They don’t mention the firebox size.

The stove may be able to put out the required btus, but for how long? You said it has a small firebox. Does this mean you’re going to be loading it every 2 hours? That’d get old fast.
Thanks for the reply. That was a concern of mine as well, and I guess a concern in general with using a cook stove as a primary heat source.
 

Bk-crow

New Member
Aug 7, 2022
4
BC Canada
Are you sure the heat loss calcs are correct? Those are very high numbers for a modern house that size. Is it made of glass? I’d expect a modern, well insulated house to need half of those numbers.
Quite possibly not, we’re still in the rough planning stages, he’s onto other projects right now and we’ll revisit this soon. I was just tasked with researching wood stove options in the meantime.

Part of the reason we were interested in running something like this is that the large outdoor boilers seemed like overkill and wasteful for the size of the house, but my husband is still set on the idea of radiant in floor heating. So we’re checking out options for indoor stove/boilers, but my suspicion is that it probably wouldn’t perform as well as we would like.
 

EatenByLimestone

Super Moderator
Staff member
There’s a specialized boiler section above that can probably answer your questions best. Many use water tanks to store heat, but your slab should do that too. You might want to ask about this up there.
 

EbS-P

Minister of Fire
Jan 19, 2019
3,553
SE North Carolina
I wouldn’t want to be a slave to my cook stove in the dead of winter. I like the cook stove with hot water loop idea. Getting domestic hot water from it would be great. Probably not for whole house heating. Getting your slab well insulated and the rest of the house too and we’ll air sealed you very well could heat it but with what reloading schedule.

I think you need have to get a real heat load calculation done. You are just best guessing, but with storage tanks you can be wrong and just oversize.

My ideal off grid home would have backup heat of some kind. Or it would be so well insulated and designed for max winter solar gain that I could heat it with a couple matches;)

Either way it would have a wood cookstove with hot water loop.

What is your design temp?
 

SteveKG

Minister of Fire
Jun 23, 2009
732
Colorado Rockies
I had a very old cookstove with a copper water tank built in. This did not work for anything but heating up some water for dish washing or whatever, as the water was accessed with a spigot-faucet. And this case, it took all day for that water to heat up, I think it was maybe 5-gal capacity. Something like that.

However, a friend had what was also an ancient stove but with piping around the firebox. He put a tank up in the attic above the stove and figured thermal action would circulate the water from the stove to the tank. Very little success; he plumbed in a circulating pump and that improved it some, but the water up in the tank still didn't get hot. Just warm.

Now, in both his case and mine, we had small fireboxes. It was a chore to keep those fires going enough to accomplish the water heating, such as it was. I now have a stove with a large firebox and no water-heating feature. I gave up and built a solar-heating system. I can imagine a stove that would do the job you want, but I predict frequent attention to the fire would be necessary. Cookstove with large firebox equals gold.

However, your research on the physics may prove me wrong.