Normally the wood boiler is plumbed to a heat exchanger see drawing above.
How to heat both my floor and sepate domestic water.
The traditional boiler water may also be used for domestic hot water by directing the water through a separate integrated water heating unit before routing it to a fixture such as a faucet or shower.
The reason for this is to have the two water uses separate.
The best kind is one that has a sealed combustion chamber and an external heat exchanger.
The two systems are basically tied together.
The open system uses one heat source your domestic water heater to provide both floor heating and domestic hot water.
The water heater to use with radiant floor heating should be a high efficiency unit.
A dual purpose system relies on only one water heater to supply both the hot water requirements for the home and the warm water needed for the radiant floor heat.
Even if only part of the home uses.
Hot water from the boiler is circulated through radiators or a hydronic heating system to warm the ambient air.
The idea here is to prevent domestic water from getting contaminated by stale water that sits uncirculated in the heating system during the off season.
In the summer water will stagnate for the floor heating and if it mixes with your regular water it won t be good.