Hello all, this is my first post. I've been studying hooking up a coil or boiler to my existing system and have only limited 'web-knowledge', which is why I'm a fan of this site. It's terrific.
(I don't have a coal stove and I'm not a HVAC guy, so my comments are worth what you've paid for them.)
Now then, the problem in hooking up a wood/coal/solar heat source is that it is uncontrollable, compared to oil or gas, which can be shut down immediately by stat, etc. With solid fuel, things melt and water boils.
I've read the masonry system report and wonder if a better job can't be done? The swing check valve and TPR are kinda patches to the problem - last-resort type safety devices that are not designed as primary controls.
The thermosyphon system described above is a 'one-pipe' steam system. My aunt still has one of these in her house. Steam rises into the radiators and cools back into water and returns through the same pipe. The oil boiler simply replaced the coal system in 1954 w/o any mods to the system. She could go back to coal anytime and its a marvel of simplicity - no pumps (other than for the burner).
Missing from some proposed thermosyphon systems is the requirement that radiators and expansion tanks have to be above the water line of the boiler. Also, steam systems (best at this no-pump thermosyphon method) require large diameter sending pipes (returns can be small stuff.) My aunt's system is all 2",3" and 4" iron pipe to the rads above.
The masonry system is a hot-water system (not steam) and I don't imagine that it works too well w/o a circulator pump. Pumps keep the water liquid instead of gas. Small-pipe systems came on scene with circulators and importantly, oil and gas burners that can be controlled.
I thought it interesting that the Brits never really got off of open, vented systems and they still use kitchen cookstoves with 'back-boilers', which they connect to CH and DHW. The best description of hooking these up safely for self-control is this .pdf: http://www.solidfuel.co.uk/pdfs/link_up.pdf
They use different terms -- the most unusual was the 'airing closet'; a tempering tank in a second floor linen closet and 'link up' is connecting your stove to CH. Check out the use of the 'neutralizer' in the first section and the control device in the second.
Pretty slick stuff, but you can't use it if you have the closed loop system, like a hot-water/baseboard system most of us have (that aren't forced air).
This is as far as I've gotten to understand all this. What I'd like to find out is what we can do to configure a hot-water system to meet the same designed-in safety and control requirements with our closed systems?
Besto, - Charlie