Patent ID: 7708010

Claim:
A method of supplying heat to a solar hot water system including a higher-temperature loop and a lower-temperature loop, the method comprising: (a) providing a transfer system for transferring heat from the higher-temperature loop to the lower-temperature loop, the transfer system comprising (i) a higher-temperature loop pump; (ii) a lower-temperature loop pump, (iii) a heat exchanger in fluid communication with both the higher-temperature loop and the lower-temperature loop; and (iv) a controller, integrated with the pumps and heat exchanger in a single unitary fixture, configured to control the operation of the lower-temperature loop pump and higher-temperature loop pump; (b) heating liquid in the higher-temperature loop with a solar heating unit; (c) delivering liquid from the higher-temperature loop to the heat exchanger, so that the liquid passes through a first side of the heat exchanger, (d) delivering liquid circulating in the lower-temperature loop to the heat exchanger so that the liquid passes through a second side of the heat exchanger, receiving heat from the liquid in the higher-temperature loop, (e) delivering a portion of the liquid in the lower-temperature loop that has been heated in the heat exchanger to an end use; (f) determining the temperature differential between the temperature of the liquid exiting the solar heating unit and the temperature of the liquid in the lower-temperature loop after it has exited the heat exchanger, and (g) controlling delivery of liquid from the higher-temperature and lower-temperature loops to the heat exchanger based on the temperature differential, to maintain a setpoint temperature differential (ΔT s ) between the solar heating unit and the end use, by: (i) calculating the actual temperature differential between the solar heating unit and the end use; (ii) turning both pumps on when the temperature differential is greater than ΔT s and running the pumps at a speed sufficient to transfer heat from the solar heating unit to the end use; (iii) turning off one or both pumps when the temperature in the lower-temperature loop after it has exited the heat exchanger exceeds a predetermined maximum; and (iv) turning off one or both pumps when the temperature at the exit of the solar heating unit falls below a predetermined minimum.