SUPER-HEAT IS AN IMPORTANT PIECE OF INFORMATION TO HAVE REGARDLESS OF THE METERING DEVICE WE ARE USING. WE WILL CHARGE BY SUPER-HEAT, BASED ON CONDITIONS (REQUIRED SUPER-HEAT), IF, WE ARE USING A PISTON OR A FIXED-ORIFICE DEVICE AT THE EVAPORATOR. WE WANT TO MONITOR SUPERHEAT ON A THERMAL EXPANSION VALVE SYSTEM TO VERIFY THE TXV’S OPERATION.

SUPER-HEAT IS A READING WE TAKE TO VERIFY HOW MUCH HEAT IS BEING ABSORBED BY THE REFRIGERANT AT THE EVAPORATOR. TOO MUCH ABSORBED CAN BE BAD, AS WELL AS TOO LITTLE. THIS ENSURES THE SAFTEY AND PERFORMANCE OF THE COMPRESSOR.

THE IDEAL SUPERHEAT RANGE WILL GENERALLY BE BETWEEN 8-15*F. BUT ALWAYS REFER TO MANUFACTURES RECOMMENDATIONS. OR YOUR SLIDE RULE.

TOO OBTAIN THIS READING, WE NEED TO TAKE A PHYSICAL TEMPERATURE OF THE SUCTION LINE NEAR THE SERVICE VALVE, AND LETS SAY WE GET A TEMPERATURE READING OF 50*F. WE THEN NEED TO CONVERT OUR SUCTION LINE PRESSURE (ON OUR GAUGES) TO TEMPERATURE. FOR EXAMPLE, IF WE ARE ON A R410A SYSTEM AND OUR SUCTION LINE PRESSURE IS 120PSI, WE WILL THEN USE OUR PT CHART AND SEE THAT R410A AT 120PSI IS APPROXIMATELY  40*F. BECAUSE WE ARE SUPER-HEATING, (ABSORBING HEAT AT THE EVAP) OUR PHYSICAL LINE TEMPERATURE SHOULD BE WARMER THAN OUR PRESSURE/CONVERTED TEMPERATURE.

50*F - 40*F = 10*F OF SUPERHEAT.

ON A FIXED ORIFICE METERING DEVICE (PISTON), THE REQUIRED SUPERHEAT CAN AND WILL CHANGE EVERYDAY. ON A TXV SYSTEM, THE SUPERHEAT IS SET BY THE MANUFACTURE AND IS USUALLY A CONSTANT.

                                                                                                CARLOS S.