A method of performance model cross-mapping in a refrigeration circuit containing at least one compressor and an expansion valve, the method comprising: measuring a suction pressure, P1, a discharge pressure, P2, a suction temperature, T1, from the refrigeration circuit and a temperature of a refrigerant before it enters the expansion valve, T3, calculating a discharge line temperature, T pm , with a first performance model as a function of the following circuit parameter values: a number of compressors, N, running in the circuit, the measured suction pressure, P1, the measured discharge pressure, P2, and the measured suction temperature, T1, from the refrigeration circuit and comparing the calculated discharge line temperature, T pm , to a measured discharge line temperature, T meas , from the refrigeration circuit to obtain a first differential value, ΔT, calculating a first mass flow, M pm , with the first performance model as a function of the following circuit parameter values: the number of compressors, N, running in the circuit, the measured suction pressure, P1, the measured discharge pressure, P2, and the measured suction temperature, T1, from the refrigeration circuit, calculating a second mass flow, M evm , through the expansion valve with a second regression-type performance model where the characteristic equation for the expansion valve is expressed as a relationship between valve mass flow, valve opening, φ, the measured suction pressure, P1, the measured discharge pressure, P2 and the temperature of the refrigerant before it enters the expansion valve T3, comparing the first mass flow, M pm , to the second mass flow, M evm , to obtain a second differential value, ΔM, and evaluating the first differential value, ΔT, and the second differential value, ΔM. measuring a suction pressure, P1, a discharge pressure, P2, a suction temperature, T1, from the refrigeration circuit and a temperature of a refrigerant before it enters the expansion valve, T3, calculating a discharge line temperature, T pm , with a first performance model as a function of the following circuit parameter values: a number of compressors, N, running in the circuit, the measured suction pressure, P1, the measured discharge pressure, P2, and the measured suction temperature, T1, from the refrigeration circuit and comparing the calculated discharge line temperature, T pm , to a measured discharge line temperature, T meas , from the refrigeration circuit to obtain a first differential value, ΔT, calculating a first mass flow, M pm , with the first performance model as a function of the following circuit parameter values: the number of compressors, N, running in the circuit, the measured suction pressure, P1, the measured discharge pressure, P2, and the measured suction temperature, T1, from the refrigeration circuit, calculating a second mass flow, M evm , through the expansion valve with a second regression-type performance model where the characteristic equation for the expansion valve is expressed as a relationship between valve mass flow, valve opening, φ, the measured suction pressure, P1, the measured discharge pressure, P2 and the temperature of the refrigerant before it enters the expansion valve T3, comparing the first mass flow, M pm , to the second mass flow, M evm , to obtain a second differential value, ΔM, and evaluating the first differential value, ΔT, and the second differential value, ΔM. <EOS>