indoor wood boiler?

Betz

boilers are relatively easy to install as an add-on to your existing furnace without the mess from soot and wood and ashes inside your house. And, with up to 3 or 4 day burn times they are pretty efficient too.

Bob Gagnon plumbing and heating

is there an inside wood boiler?

I need to buy an insert wood stove for my fireplace, can I get one with a coil to add supplemental heat to my 1500 gal solar storage tank? or will there be too much creosote in my chimney, or too much smoke in my house? thanks, Bob Gagnon

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hr

Some of those

inserts will suck more heat out of the house than they add. Make sure you get a sealed one with combustion air from outside.

The biggest problem with the old hydro grates was the ability to turn to steam if the circulation would quit! A very small volume of water in those coils.

An old timer once told me there is a stick of dynamite worth of energy in a gallon of water that flashes to steam. Becareful with any homemade devise Yes too big of a HX could drawn down the flue gas temperature and lead to creasote issues. Hard to know how much HX to build into a fireplace like that.

Central Boiler (the outdoor furnace folks)used to make a unique free standing gas log boiler with glass doors as a decorative piece. The Millennium I believe. Haven't seen one in years. They used to drag them to the early RPA events.

hot rod

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Dan Peel

inserts

If you have the extra depth or can sacrifice some width your best choice is an exchanger external to the firebox. Any of the finned coils can extract heat from the heat path and are adjustable enough in their proximity to the stove surfaces to prevent the kind of explosive issues Hot Rod refers to. Several regional suppliers through the years have offered saddle coil kits for both free standing and insert type wood appliances. The market is a bit narrow from a commercial standpoint. Enjoy....Dan

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JackFre

Holly Hydro heater

Do not know if it is still made but Bill Hollobaugh of Santa Rosa CA made a 2x6x12,18 or24 which could be inserted into the top of a wood stove. Worked well, but...Hot Rod is correct about the flash issue. I used to line up relief valves to back each other up. If you are lucky with the layout you could maybe have a drain down to the tank

RC

Indoor wood boiler

Buderus makes an indoor wood boiler. look it up on the website

RC

Indoor wood boiler

Buderus makes an indoor wood boiler. look it up on the website

Bob Gagnon plumbing and heating

indoor wood boilers

are no longer available from Buderus or Central. do you think piping homemake one like this will be O.K.? I'll take my supply and return from below the waterline on my non-pressurized tank, trap my grundfos 15-58 circulator so it stays full of water, pump up to maybe 12' of baseboard element behind the wood stove? My solar heating is working better than expected, and with some wood, I may not have to turn on my oil boiler at all. Thanks for your help, Bob Gagnon

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Joe@buderus

Wood Boiler

Bob, Buderus does not offer the wood boiler anymore, but our wood boiler manual has a couple of suggestions for piping and controls. If you e-mail me, I will forward the information to you.

Bob Gagnon plumbing and heating

thanks, Joe

but your store in Londonderry N.H. already e-mailed that file to me. you people are so helpful. Anyone have any ideas on open vs closed loop w/ a coil? boiling dangers vs mineral buildup from 1500 gallons?

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hr

Don't think mineral

build up would be a problem, seeing as you are not adding new water, and minerals, constantly. You might consider a bronze or stainless pump for that open loop just to keep the rust and build up issues in a ferrous bodied pump at bay.

I think some bare copper tube fastened to the back side of the insert would be my choice. This way you get a much stronger (conduction) transfer as opposed to the air to air concept with finned baseboard. I doubt that it would ever boil on the back side of the insert box? Can't imagine the otter shell of the insert box gets that hot. Hard to say without seeing the construction

Years ago I built a barrel stove with a 1" iron pipe loop inside as a hydro grate. Yes, it did boil. Often!

So next I wrapped two loops of copper around the outside of the barrel, instead, and it was much more control-able than a HXer right in the hot coals.

hot rod

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Royboy

external heat exchangers

are preferable in my estimation, for safety reasons. I've done lots of internal heat exchangers in wood stoves but always with convective delivery to storage (not dependant on electricity but storage can't be below the heat source). Downside to external is that much less heat is available and so you might find that hot rod's copper lines (or some other conducting pickup HX) works better - or maybe you just use lots of fintube.

Roy

Dan Peel

not fin tube

The results are far more gratifying with the use of a water to air exchanger - the cased coil type found in hydro-air setups. These compact units with 12 to 14 fins per inch can coolect and deliver good volumes of heated fluid without compromising the code approvals of the wood burning appliance. Mounting these externally works without condensing the firebox or cooling the smoke path. Enjoy......Dan

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hr

I follow your logic Dan

but wouldn't it need to be a forced convection, i.e. a fan assisted, coil to transfer much air to water BTUS? If not a cased coil looks like a bunch of fin tube glued side by side

Would the coil need to be in a pretty warm, maybe hot, air stream to work air to water? As a car radiator needs fan assist when not moving. Would it be hot enough external to the insert fire box to transfer much into the fluid stream?

I started reading up on coil construction at the Mcquay site. Wow, lots of enginnering goes into coils design! Spacing, thickness of coil material, shape of fins, rows of coils, rows of fin, rifled tube within the coils, etc,etc. Seems a lot more complicated than I imagined.

The coil manufactures are always trying to wring more heat into an air stream and new designs are always being tested. Interesting stuff. Lots of math to design the ideal coil configuration.

Not cooling the fire box and hense the chimney is important. I use a 140° stat to stop pump flow through the wood fired boilers, in an effort to keep the temperatures up beyond condensing. This, and or, a thermostatic mixer on the return to the boiler are a big help. I imagine a similar control with a set point control could monitor the inset internal and flue temperature, shutting down the air to water exchange pump, or fan, until the box got hot

hot rod

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Dan Peel

Mostly right.

You don't want forced convection - you want the coil in the heat path, not the air path, to accumulate the heat for the water to extract. In pratice a spacing of about 1" from the firebox to the face of the coil works for most I've played with. The same ideas work quite well inside the plenum of a wood furnace to supply heat or preheat for DHW - the temperature never gets over 180 when you place the coil right so no controls are required. It's radiant heat, sort of like solar, except it's dark, comes from hot steel plate, and works whenever you have a good fire going. Another style we've used is the PLATECOIL out of Wichita Texas - these are mostly used to extract heat from masonry chimneys. Lots of fun stuff out there.......Dan

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