[Greenbuilding] masonry stove and radiant floor heat?
keith at earthsunenergy.com
Fri Jul 27 09:00:20 EDT 2007
Thanks Norbert, I get people asking about that all the time, and what I
mostly notice is the absence of any off the shelf choices, and warnings
about older versions of wood water heaters that used to blow up... The
links to masonry boilers were very interesting too.
Norbert Senf wrote:
> At 10:55 AM 6/27/2007 -0400, Bill Hutchins wrote:
>> any way to heat water for radiant floor tubes
>> w/ a masonry stove, such as Tempcast?
> A belated response:
> Hydronic heating using a masonry heater sounds like a good idea,
> and we get a lot of inquiries about it. It is not that easy to do.
> It is fairly easy to install a small heat exchanger directly in the
> hottest part of the firebox, where you can take off enough to do a
> significant amount of domestic hot water. However, taking off more
> is a problem. You can't do it directly in the firebox, because it
> will cool the fire and affect combustion. This is why many outdoor
> boilers burn so extremely dirty - because they are basically a water
> cooled metal firebox.
> Also, bear in mind that a masonry heater burns in batch mode, and
> is designed to handle a certain amount of wood per burn. Assuming
> a constant efficiency, a given weight of wood translates into
> X BTU's of heat. If you take some of that heat off with a coil and
> put it somewhere else, you are not getting any more heat, just moving
> it around. With a reasonably sized, low energy house, it is worth
> questioning whether you need to move heat around at all, since these
> houses naturally tend to have less stratification, and heat distribution
> is much less of an issue. Particularly, if the house is designed to
> be fairly open, and the heat source is centrally located.
> If you DO want to try hydronic heating, first of all you have to accept
> the fact that it is still at the experimental stage, and that you are
> signing up to be a guinea pig. The basic idea is that you have to move
> the heat exchange downstream from the combustion zone. Since the temperatures
> are lower, you need more heat exchanger. Theoretically, this also gives
> you a higher capacity heater that you can fire harder. However, you will not
> get a manufacturer to warrantee this application.
> You also need a hydronic system designer or plumber who is willing to
> take responsibility for the design and installation. UL listed components
> are not available for the application. I did
> check the Canadian CSA boiler code,
> and it states that if you keep water temperatures under 150F, then boiler code
> does not apply.
> One strategy that some people use is to put the
> hydronic tubing in when they pour
> their slab, but to leave the expensive
> controllers, etc., until later until they
> decide whether the hydronic floor is needed at all.
> In my view, really the application is not a good
> match for a conventional masonry heater.
> What you really need is a boiler. A boiler can, in fact, be masonry and burn in
> batch mode. Igor
> Kuznetsov is an engineer in Russia who has
> designed a lot of masonry boiler systems,
> as well as having developed a very innovative
> masonry heater system based on gas
> buoyancy. He has an informative website http://stove.ru/index.php?lng=1
> and an article on masonry boiler design located here:
> Best ...... Norbert
> Norbert Senf---------- mheat(at)heatkit.com
> Masonry Stove Builders
> 25 Brouse Rd.
> RR 5, Shawville------- www.heatkit.com
> Québec J0X 2Y0-------- fax:-----819.647.6082
> ---------------------- voice:---819.647.5092
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