Abstract: Apparatus and methodologies are provided to monitor temperature from at least two locations on an evaporator in a refrigeration system. Operational characteristics of one or more of the compressor, condenser and evaporator cooling fans are adjusted based on the difference in temperature between the two locations on the evaporator. In some systems a second evaporator may be provided along with a refrigerant control valve. Cooling air flow across the second evaporator and refrigerant distribution between the plural evaporators may also be control.

Abstract: A hot water heater, and method of regulating the same, which includes a PID control. The PID control is responsive to inputs such as water temperature in the hot water heater and the flow rate of water such as through inlets and outlets coupled to the hot water heater. In one embodiment, the PID control generates an output that modifies the operating parameters of a heating device to accommodate changes in the temperature of the fluid in the hot water heater. The output results from one or more modules of a three-term control structure, wherein the modules comprise one or more of a proportional control module, an integral control module, and a derivative control module. Each of the modules is assigned at least one term, wherein the term is defined in accordance with gain parameters such as a proportional gain, an integral gain, and a derivative gain.