A CLOSED RADIANT SYSTEM:
In a Closed Radiant System, the heating fluid is self contained. The fluid stays there unless removed for maintenance. The closed system and the potable domestic water source are not connected. A baseboard heating system using a boiler is one example of a closed system.
A boiler or water heater warms the water or another fluid such as anti-freeze. When the thermostat calls for heat, a pump is turned on and circulates the warm water throughout the floor until the thermostat is satisfied.
For proper installation, install a Plumbing Mechanical Package (PMP). This device includes fill and drain valves, shut-off valves, an air eliminator, pressure relief valve, and pressure gauge. The system requires an expansion tank.
Closed systems are familiar to code officials and contractors, and they encounter little resistance. You can combine a closed radiant system with baseboard radiators.
Radiantec recommends using a quality domestic water heater instead of a boiler in underfloor radiant heating systems. There are many good reasons for this such as:
1. Boilers make very hot water by design. Domestic water heaters make moderate temperature water by design. The task associated with radiant heat is to make moderate temperature water and there are many benefits in doing so.
2. There is no need for an expensive mixing valve or special controls to lower the water temperature.
3. Domestic water heaters withstand the thermal shock of a large quantity of cold water dumped into them. Boilers are not.
4. Condensation does not affect a quality domestic water heater. Condensation damages most boilers.
5. Condensing water heaters operate with exceptionally high efficiency (95+%). Most boilers cannot match this.
6. A quality domestic water heater typically costs less than the equivalent boiler.
7. Domestic water heaters have very high initial heat output due to the heat stored within the tank. This will increase the responsiveness of the system.
8. Quality domestic water heaters can direct vent into plastic pipe instead of into an expensive chimney.
Radiantec_Closed_Radiant_Heating_System_Installation_Manual