Modulating Three-Way
Diverting Valve
This is the most commonly selected method for regulating the boiler water. A self-operated control valve allows only the required amount of boiler water into the heating coil in order to satisfy the demand. Any excess boiler water is diverted back to the boiler water circulating loop.

On/Off Modulating Valve
This control system will allow only the required amount of boiler water into the coil to satisfy the demand. As the water temperature in the tank approaches the set point, the flow of boiler water to the coil is decreased. This control valve does not divert unused boiler water back to the circulation loop.

Pump On/Off Control
This control system operates via a thermostat which opens or closes the control circuit to an independent boiler water circulation pump. The thermostat is wired into the control circuit of the circulation pump and will close the control circuit when heat is required (thereby turning the pump on) and will open the control circuit when the water temperature in the storage vessel reaches the thermostat set point, thereby turning the pump off.