“There are hot water coils designed to fit inside traditional free-standing woodstoves, and hydronic water jackets designed to fit inside a conventional masonry fireplace”

Brad

Brad,

I have answered this question before.

Stricter Federal government regulations and easy lawsuits against manufacturers have driven all the manufacturers of this type equipment out of the US market.

Back in the 70′s and 80′s there were many manufacturers of wood-fired hot water heaters, hydronic fireplaces, and hot water coil inserts for wood stoves.  Some moved to Mexico and are selling lots of these products in Mexico and others just went out of business.

There may be one or two left, but about the only water heating wood stoves made now are the outdoor wood-fired boilers you see advertised in this magazine that pipe the hot water into the house.

Hope this helps,

Jeff Yago

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I am looking at replacing a traditional fireplace with a wood stove insert that can be used in a hydronic floor system.

I looked over your article on the fireplace you installed in your home and have spoke to and web searched for wood stoves that circulate water for heated floors and find only the “long burners” for outside or commercial “furnaces”, nothing that would be appropriate for a great room/ranch application.  Can you point me toward manufacturers that have this type of product?

Thank you.

Mark J. Bechtel

Mark,

Jeff Yago

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I have a fireplace in my basement and wood like to augment my propane/hydronic heating system with a wood stove fireplace insert similar to your setup. My question is about the water jacket that you use. Is it off the shelf product? Custom? Can you provide insight into the set-up that you did not detail. Your expertise would be appreciated!

Thom Pecoraro
Stephentown, NY

Thom:

This is another great example of class action lawsuits forcing great products off the market.

Throughout the 1970′s energy crisis there were several nationally sold fireplace inserts and fireplace grates that heated water. This made it easy to pipe all the wood heat to hydronic baseboard heaters in other parts of the house, or to a hot water coil in the ductwork and heat the return air being ducted to the other rooms without operating the electric strip heaters or gas burners. I purchased several of these “Hydro-Heaters” for other projects, including the one I now have in our solar home. I had it the new unit boxed up and put in storage for almost 15 years, then installed it in 1992, and it has worked perfectly for the past 16 years.

There also was a firm in northern California I visited in the late 1990′s that was making a great wood-fired hot water heater for remote home-sites. It looked like a standard gas hot water heater, but the bottom half was a fire-box and the flue went up the center. You built a small wood fire and waited about 30 minutes, then you had enough hot water for several showers and dish-washing. They made a “tank-less” version that was just a fire-box surrounded by a water jacket, and you pumped the heated water to a larger storage tank or hot tub. I also purchased one of each and am still keeping them for future since this firm is now out of business and to my knowledge was the last company still making these in the US.

What happened was most state and federal agencies viewed these products the same as a steam boiler since they can explode if not properly installed. For example, all of the models that were sold in the 1970′s always came with a temperature relief valve and a pressure relief valve. If you have a large fire going and the water pump stopped pumping when the power went out, without any water flow the water jacket would quickly turn all water still left in the heater to steam. I have witnessed several times when this happened and all the only thing you saw was some some steam safely venting to a floor drain or outside. However, if the relief valves were not properly installed, the pressure could reach a level that would rupture the steel jacket or under extreme cases even explode. There were not only cases of tank ruptures due to missing relief valves, but even a few cases where a relief valve was piped to the outside and a small drip through the valve due to a weak spring would run down the pipe and freeze during winter weather. After several days the relief valve’s discharge pipe would totally plug up with ice, then if the pressure increased due to a power outage stopping the pump there was no place for the pressure to vent.

I know that there are millions of these wood fired hot water heaters and hydronic fireplace grates being sold in third world countries every year, and I think the California manufacturer moved his operation to Mexico years ago, but I am not aware of anyone making a hydronic fireplace insert that is legal today. If any reader out there can provide this information we all would be grateful, but I think the cost to get these UL listed and the cost for liability insurance for any manufacturer makes this impossible today.

If you really want to heat your home with wood using a hydronic system, I suggest installing one of the many outdoor packaged units you see advertised in Backwoods Home, and in an article I provided on this subject. Since these outdoor units use a non-pressurized water jacket system to pipe hot water to heat the home, they are safe and easy to install.

Good Luck!

Jeff Yago

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Tom:

Although it is possible to design a heating system that does not require any pumps or electric devices to operate, there are many technical reasons why this will not do what you think it will.

First, older gravity flow hydronic heating systems worked because their piping was large and routed to promote proper flow. Second, they used a very hot 180 degree water temperature to create the large temperature difference required to create the flow. A typical glass-lined residential water heater is usually heated to only 125 to 130 degrees which will not have much temperature difference to produce the flow, and most hot water tanks are not designed to operate at 180 degrees without damage to the glass lining.

Another issue is normal flow direction. Since you would be connecting the supply pipe from the discharge side of hot water tank up to the heating appliance and the return pipe back to the inlet side of the hot water tank, this is a dead short across the tank. This means when you open a faucet somewhere in the house, the water can flow “backwards” from the cold line into the hot line by passing through the appliance.

Why not install an externally vented gas wall heater that uses a non-electric igniter? You could locate in an central area.

Good luck,

Jeff Yago

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Keven:

As I mentioned in the article, we designed several systems that used a storage tank. Tank water was heated from the hydronic wood stove which was then circulated later at night to circulate to the home’s floor slab after the fire was out. Most of these tanks were under 1000 gallons since they would be located in the garage, and they took about 4 hours of a really big fire to heat up. If you had a 10,000 gallon tank, it must have taken days to get the water hot, but then you would be able to heat for days without a fire once it was!

We used standard 3/4″ copper which come in 60 foot rolls for our heat exchanger and placed two coils in the tank which kept the water that circulated through the stove and coils from mixing with the water that stayed in the tank. All of our systems required two pumps and three automatic zone valves to re-direct the flows since you need three separate operating modes: stove to tank, stove to house, and tank to house. If you were able to do all this without any pumps or valves, you must have had a really good thermo-syphen effect with your hydronic stove.

Thanks for the description of your very large system.

Jeff Yago

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