1. Heat Source (Tank type water heater, condensing boiler, electric boiler, thermal storage tank)
2. Circulator Pump
3. Thermostat
4. Distribution Piping
5. Expansion tank
6. Air separator
7. Switching Relay (not shown)
8. Transformer (not shown)

In this form of heating the heat source and the radiant panel are directly connected in the same piping circuit. A heat source that can withstand relatively low water temperatures without being adversely affected by flue gas condensation is required. These heat sources include tank type water heaters, condensing boilers, thermal storage tanks, and electric boilers.

The supply water temperature is controlled by cycling the heat source on and off. When the temperature leaving the heat source goes above the required panel temperature a high limit control temporarily stops the heat source from producing more heat. However, the distribution circulator continues to run. The radiant panel then dissipates the heat stored in its thermal mass into the space to be heated. The heat from the heat source, and in the pipes is also dispersed. Therefore the system temperature is decreasing as heat leaves the distribution system. The rate of temperature decrease is dependent upon the thermal mass of the system. A concrete slab will have the highest thermal mass while suspended pipe will have the lowest.

The heat source is turned on again as needed to maintain comfort in the building. This cycling of the heat source continues until the space no longer calls for heat. Ultimately when the thermostat is satisfied the heat source is turned off. The circulator may or may not continue running at this point. Continuous circulation is often preferred as it reduces temperature swings in the space to be heated.