Originally Posted by 
JDNSW
				 
			The kitchen stove has a purpose designed water boiler which surrounds all sides of the firebox (except for the firedoor opening, about half the front, and the top and bottom). This is plumbed via a small circulating pump and a branch to the hot water system to a double manifold about two feet above the floor in the middle of the house. From this manifold there are six double spirals of pipe (a special low density poly pipe sold for the purpose) within the slab. The pipes were laid out on top of the reinforcing and wired to the mesh about every metre. The slab had to be thicker than normal by the diameter of the pipe (20mm), and the system was filled with water to stop it lifting when the slab was poured. 
There is a small header tank with a ball valve to provide pressure relief and ensure the system is kept filled. (This is essential to prevent the possibility of explosion.) Each separate circuit is provided with a control valve which allows regulation of heat to different areas of the house. The circulating pump is controlled by two thermostats plus a switch - one thermostat keeps the pump off until the water returning from the hot water system reaches the set temperature, and the other switches the pump on regardless when the water rising from the stove approaches boiling point.
I would doubt that you would get enough heat from an open fire, although I suppose it depends on how big the fire is.
Hope that helps,
John