Recirculating fluid heating systems

A liquid heating system comprising:

• (a) a reservoir;
• (b) a cold liquid supply communicating with the reservoir;
• (c) a heater having an inlet connected to the reservoir and an outlet connected to one or more fixtures;
• (d) a heated liquid return connection connected between the outlet of the heater and the reservoir;
• (e) a pump connected in series with the heater, whereby the pump can draw liquid from the reservoir and impel the liquid in a predetermined downstream direction through the heater and through the return connection to the reservoir;
• (f) a controller operable to actuate the heater to supply heat to liquid passing from the inlet to the outlet so as to bring the liquid at the outlet to a setpoint temperature, the return connection and pump being constructed and arranged to permit liquid flow from the outlet of the heater to the reservoir but prevent liquid flow from the reservoir to the fixtures through the return connection, and
• (g) a temperature sensor operative to detect a temperature of liquid passing out of the heater, wherein the controller is operative to adjust the heating rate applied by the heater so as to maintain the temperature detected by the sensor at the setpoint temperature, wherein the controller is operative in an idle condition, while no liquid is being drawn from the system, to deactivate the pump and the heater when the temperature detected by the sensor is at or approximates the setpoint temperature and the heater is not supplying heat, then reactivate the pump after a period of deactivation regardless of the temperature detected by the sensor, and then, responsive to the temperature detected by the sensor, either (i) maintain the pump in operation and activate the heater or (ii) deactivate the pump again.

A liquid heating system comprising:

• (a) a reservoir;
• (b) a cold liquid supply communicating with the reservoir;
• (c) a heater having an inlet connected to the reservoir and an outlet connected to one or more fixtures;
• (d) a heated liquid return connection connected between the outlet of the heater and the reservoir;
• (e) a pump connected in series with the heater, whereby the pump can draw liquid from the reservoir and impel the liquid in a predetermined downstream direction through the heater and through the return connection to the reservoir;
• (f) a controller operable to actuate the heater to supply heat to liquid passing from the inlet to the outlet so as to bring the liquid at the outlet to a setpoint temperature, the return connection and pump being constructed and arranged to permit liquid flow from the outlet of the heater to the reservoir but prevent liquid flow from the reservoir to the fixtures through the return connection,
• and
• (g) a temperature sensor operative to detect the temperature of liquid passing from the reservoir to the heater, wherein the controller is operative to adjust the heating rate applied by the heater responsive to the temperature detected by the sensor so as to maintain a temperature of liquid passing out of the heater at the setpoint temperature, and wherein, operative in an idle condition, while no liquid is being drawn from the system, the controller is operative to deactivate the pump and the heater when the temperature detected by the sensor is at or approximates the setpoint temperature, then reactivate the pump after a period of deactivation regardless of the temperature detected by the sensor, and then, responsive to the temperature detected by the sensor, either (i) maintain the pump in operation and activate the heater or (ii) deactivate the pump again.