Radiant heat retro-fit

[Ralph Day]

I'm thinking, with my insulated but unfinished basement, woodstove down there, easy access, i might be able to rig up some radiant heat (under upstairs tile floors) with the wood heat as primary heat source. Just wondering what i'd be getting into...fluid dynamics, pressure suystem, holding tank/open system, all that stuff.

Any coments/advice welcome.

Specifics: about 600sq ft of accesible basement ceiling for radiant heating above. Waterford cast iron stove with top plate about 2ft sq for heating water. power available for running pumps etc...limited (off grid home, must keep loads down). Stove runs from mid Oct to May, is primary heat source for the house in a radiant/warm air kind of way. Hoping this might add/harvest some BTU's during the nighttime hours largely.

Thanks to any and all

Ralph

Ps Paul, the plates an tubes in another thread...are they yours?

[Ric Murphy]

Hi Ralph,
I don't have any personal experience with what you're considering but my x father in law has built a couple of them. The both work very well and have been functioning for many years. In his case he designed and built the fireboxes too and incorporated stainless steel coils in the ceiling of it. The box was designed as a fireplace insert vs a stove. The one system was connected to his radient hot water heating system. It would have had all the whistles and bells that a typical hot water heating system would use. In your case assuming first that you can somehow add a coil to the heat chamber of your existing stove, I think you could achieve what your after quite simply. I don't know why you can't just connect a pump and a vented holding tank to typical radient floor heating system. I wouldn't think the holding tank even needs to be insulated. As long is the pump is below the tank full level it will stay primed. The system pumps back into the vented tank so airlocks or pressure build up should not be an issue. The vented tank would create humidity but thats usually a bonus with a wood stove. The evaporated water would have to be replaced. You could make the entire thing manual (pump on/pump off) or add various degree's of automation. Like I said at the start I don't have first hand experience with hot water heating systems but will be getting into it soon once I finish up my solar panels. My son is working on a self contained, outdoor, wood fired boiler. We had a conversation on this subject just this very afternoon...go figure!!!
Ric

[Stewart Corman]

First to answer Ralph:

I really don't understand what you are trying to accomplish.
You burn x amount of wood to provide y amount of temperature comfort.
There is z amount of heat lost up the chimney.
If you don't burn any more wood, you won't get anything any warmer.
How much of an investment are you planning and for what real benefit??

If you already have the woodstove in basement, the heat rises to the basement ceiling and should warm the entire floor above w/o any more contraptions (unless ceiling is insulated??). My basement fireplace/furnace does exactly that. Only trick is to insulate as much as you can around the basement walls/windows...so I don't see what you really expect to gain. A stack heat exchanger is the only adder that I see that can keep heat from going up the chimney ...and not the cheapo sheet metal variety ...I have some pics posted:
http://i145.photobucket.com/albums/r203/scorman1/fireplace/4816.jpg
details upon request

BTW, I run my TECO hot water baseboard circulator pump 24/7 ...uses about 20 watts to answer one of your questions

Slightly OT : here is a link to aluminum tubing supply ..can use compression couplings but compare to copper prices:

http://www.plumbersurplus.com/Cat/Aluminum-Utility-Tubing/269/List?attribute_value_string|Brand=D.O. +Smith (http://www.plumbersurplus.com/Cat/Aluminum-Utility-Tubing/269/List?attribute_value_string%7CBrand=D.O.+Smith)

Next to comment to Ric:
I have seen a commercial outside wood burner in action and thought it's design was quite slick ..this past week Otherpower has had several discussions and most claim that they are VERY inefficient requireing 12 full cords to heat a house ...my indoor unit uses 5+ full cords for 2750 sqft ranch ..do some DD over there

Stew

[Mark Parsons]

Hi Ralph,

I will be supplementing my SDHW system in winter with woodstove warmed water. I know you have the SDHW system in place with heat exchanger and recirc pump so is very easy to use same infrastructure.

My research indicates that putting coils in the firebox area of the woodstove is not a good idea. Too much lowered temperatures causing incomplete combustion and added creosote generation. Not too mention that even stainless steel tubing doesn't stand up for very many years in that environment.

My plan is to bend 3/8" copper tubing into tight 'S' forms and clamp to the outside of the woodstove. Clamp to 2 sides of the stove with some threaded rod and aluminum bar stock. Not pretty, but all painted black shouldn't look too bad. Use my existing solar drainback pump through some added valves to direct into the woodstove loop and through my sidearm heat exchanger as normal. This DHW could easily be plumbed into hydronic heating circuits.

As Stew points out you are already getting all the btu's from your woodstove you need for space heating. If you needed more DHW in the winter, the woodstove loop would help to keep the propane bill down for your tankless water heater.

Regards,
Mark

[Ralph Day]

Thanks for the replies folks.

I think what i'd have envisioned would be a re-distribution of btu's from the stove. Instead of just radiant/convection heat into the air and structure, i'd be driving heat directly to areas only getting heated by warm air. Just a thought.

Mark, I was thinking of a vessel on top of the stove, kind of like a pot, but hadn't thought of the difference in height of the vessel and the lines. If the lines are higher, they'll drain into the pot etc etc. And nothing in the firebox, there's no room anyways! Modern airtights have little space in the fireboxes, not lke the old Fisher's and Lakewoods.

ralph

[Paul Bailey]

See Attached word Document.. Now as far as the numbers go . Radiant is the fasted growing heat median on the eastern seaboard of North America. (40% sales increase per year) Economics of the Efficiency are a key factor here in these decisions as Fuel costs are on the rise and radiant delivers Key performance advantages that just dont happen by heating Air.. More to follow.....Paul. (hate to sound like a sales guy here But, having Stepped into a few houses with radiant and you just know its right, these systems also integrate well with GX , Solar Hot water, heating water with Wood, and radiant cooling as well)

[Paul Bailey]

My research indicates that putting coils in the firebox area of the woodstove is not a good idea. Too much lowered temperatures causing incomplete combustion and added creosote generation. Not too mention that even stainless steel tubing doesn't stand up for very many years in that environment.



My friends stainless coil has been in the top of the firebox close to 18 years and performing as new. . You are correct in stating that interferance of Anything cold in the box will affect the burn and the efficiency..Paul
:) Mark > there is some peace of mind as well by having all the coils external for safety reasons. Reminds me of a story of a Findley Oval with a water jacket that launched the Front out through the front door of the farmhouse when the Temp and pressure releif failed.

[Paul Bailey]

Here is a Stainless 316L Schedule 40 coil designed for my woodstove but not installed yet. It totals 62" (155 Cm) and supposed to deliver 10,000 BTU per hour max.

[Mark Parsons]

Hi Paul,
Does the SS loop you made fit inside or outside your airtight? Is it designed to be drainback?

Hi Ralph,
Are you thinking of going with thermosyphon action for your radiant coil? I suspect flow may be too low to accommodate anything more than a hot spot, but not sure.

Regards,
Mark

[Paul Bailey]

Hi Mark : It is for inside the stove ,across the back and the left side tight to the fire brick at the very top. Unless you were looking for it you would never Know it was even installed. This IS a factory designed and certified ( By ULC or the likes of CSA,cannot remember who did the testing ) for water heating in this particular stove. Hard to find a stove today with this option I think> Paul:)