Corn furnace, radiant in-floor

Currently have in-floor radiant tubing in basement and in sand on main floor of 2300 sq ft house in North Eastern Ontario. Boiler supplies in-floor water as well as domestic hot water (closed system).
Thinking of installing a corn furnace outdoors and want to tie that into the existing radiant heating. Will be about 100′ from the corn furnace to the basement boiler.
Most often the corn furnace will run during the winter, but if we were to go away for the weekend, the corn furnace will go out and then want the oil boiler in the basement to take over.
How does one arrange to have the system know when to fire up the oil boiler or to draw heat from the corn furnace ?
The in-house system is on a 15lb pressure and the corn furnace will be without pressure in understand, so what is the best way to get the heat from the water in the corn furnace to the water in the in-house system. Some kind of heat exchanger ?
What makes and models of corn furnaces have you installed ? Anyone in Ontario ?
Would appreciate comments from anyone with experience in this area so that I can start doing some research and talk intelligently with my installer (who is new to corn furnaces also).
Replies
there are plenty of info on the internet.
just want to share where you can buy a heay exchanger for a corn furnace:
http://www.brazetek.com/products