Patent ID: 8322155

Claim:
A method of calculating net sensible cooling capacity of each of a plurality of cooling units within a data center, each cooling unit of the type comprising a compressor, a condenser in fluid communication with the compressor, a thermal expansion valve in fluid communication with the condenser, an evaporator in fluid communication with the thermal expansion valve, a hot gas bypass valve in fluid communication with the compressor and the evaporator, and a controller, the method comprising: measuring a discharge pressure of fluid from the compressor and a suction pressure from the evaporator; calculating a condensing temperature of fluid flowing from the compressor and an evaporating temperature of fluid flowing from the evaporator; calculating a mass flow rate of fluid flowing from the compressor; calculating enthalpy of fluid flowing from the compressor, of fluid flowing from the thermal expansion valve, and of fluid flowing from the evaporator; calculating a mass flow rate of fluid flowing through the hot gas bypass valve; calculating net sensible cooling capacity of each cooling unit, wherein the calculating is performed by the controller in each cooling unit, and wherein the controller in each cooling unit is configured to reduce the net sensible cooling capacity by bypassing hot gas at the bypass valve back to the evaporator, and wherein the controller in each cooling unit includes firmware comprising a program control loop; measuring a parameter of the bypass valve, the parameter being a pressure differential; and manipulating the operation of the bypass valve when the parameter is above a predetermined threshold, wherein determining the pressure differential is achieved by measuring the pressure of fluid flowing through a discharge pressure sensor and measuring the pressure of fluid flowing through a suction pressure sensor.