This system uses a high efficiency water heater or boiler and the heating fluid is self contained within the system and stays there unless removed for maintenance. The heater warms the water or another fluid such as anti-freeze. When heat is called for by the thermostat, a pump comes on and circulates the warm water throughout the floor until the thermostat is satisfied.
- Very well accepted by code officials because the domestic hot water is completely separate.
- Easy to have a combination of high temperature applications such as baseboard and low temperature applications such as radiant.
- Mechanically very simple.
- Anti-freeze can be used if desired.
- Having redundant systems can be beneficial; if your heat fails, you still have hot water for showering and vice versa
- Slightly more expensive than the Open Direct System because you need a separate water heater for domestic purposes.
- Free cooling benefit is eliminated
- Oxygen barrier tubing is often required if a boiler is used.
- The system may not be quite as efficient if a boiler is used. See water heater vs. boiler
Closed System Example