Sabbath controller for a hot water tank

A control unit for a water heating system, wherein:

• the water heating system comprises:
• a tank for holding a volume of water, said tank having a hot water outlet and a cold water inlet connected to a main water supply whereby hot water removed from the hot water outlet is replenished with cold water,
• a temperature sensor for providing a temperature signal indicative of water temperature in the tank,
• a heater for heating the water in the tank, and
• a controllable shut off valve connected to the water inlet;
• wherein the control unit comprises:
• a sensor input for coupling to the temperature sensor,
• a valve control output for coupling to the shut off valve, and
• a controller configured to monitor the water temperature based on the temperature signal and being responsive to a Sabbath mode of operation for periodically actuating and de-actuating the heater while maintaining an average water temperature to less than a permitted preset threshold, and for closing the shut off valve when the heater is actuated and for opening the shut off valve when the heater is not actuated.

A water heating control system comprising:

• a tank for holding a volume of water, said tank having a hot water outlet and a cold water inlet connected to a main water supply whereby hot water removed from the hot water outlet is replenished with cold water,
• a temperature sensor for providing a temperature signal indicative of water temperature in the tank,
• a heater for heating the water in the tank,
• a water pump coupled between the water outlet and the water inlet for re-circulating water in the tank,
• a control unit that monitors the water temperature based on the temperature signal and is responsive to selection of a Sabbath mode of operation for periodically actuating and de-actuating the heater while maintaining an average water temperature to less than a permitted preset threshold, and
• a controllable shut off valve connected to the water inlet;
• wherein when set to the Sabbath mode, the control unit is configured to close the shut off valve when the heater is actuated and to open the shut off valve when the heater is not actuated.

A water heating control system comprising:

• a tank for holding a volume of water, said tank having a hot water outlet and a cold water inlet connected to a main water supply whereby hot water removed from the hot water outlet is replenished with cold water,
• a temperature sensor for providing a temperature signal indicative of water temperature in the tank,
• a heater for heating the water in the tank,
• a control unit that monitors the water temperature based on the temperature signal and is responsive to selection of a Sabbath mode of operation for periodically actuating and de-actuating the heater while maintaining an average water temperature to less than a permitted preset threshold,
• a controllable shut off valve connected to the water inlet, and
• an override switch, operation of which during Sabbath mode causes the control unit to open the shut-off valve for a predetermined time;
• wherein when set to the Sabbath mode, the control unit is configured to close the shut off valve when the heater is actuated and to open the shut off valve when the heater is not actuated.