The choice of a compressor for a certain piece of cooling equipment depends primarily on two factors.
01. Control element
As we have seen, all the cooling system needs an element of control, which may be an expansion valve or a capillary tube. In circuit equipped with a capillary tube, the pressure in the suction and discharge sides equalize during the shutdown of the compressor. In this type of circuit, the compressor is powered by a motor that has a low starting torque.
Whereas, in a circuit with an expansion valve, only coolant flows through the valve when the compressor is on. After a while, the pressures between the suction and discharge do not equalize. In this case, the compressor is equipped with a motor with a high starting torque.
The compressor Motors suitable for these two systems are called:
LST - Low starting torque, used in capillary systems.
HST - High Starting Torque, used in systems with expansion valves.
02. Evaporating temperature
Another factor that influences the choice of the compressor is the evaporation temperature range that the system requires. We can point out two extremes:
- Freezers operating at very low temperatures ranging from -25°C to -35°C.
- Dehumidifier that works with an evaporation temperature above 0°C.
The heat absorption by the refrigerant will depend on the evaporation temperature.
A certain temperature in the evaporator corresponds to a certain pressure. The gas density is low at low temperatures and therefore only a small amount of heat can be absorbed during evaporation. If the evaporation occurs at a higher temperature, for example, 0 ° C, the pressure and density increase and the amount of heat will be greater.
For this reason, we can conclude that the work done by a compressor motor will be higher than that achieved by the same compressor at a low evaporation temperature.
Consequently, motors for application in high-pressure evaporation systems should have a higher operational torque.
Compressors can be classified according to their application:
- LBP - Low Back Pressure - Low evaporation temperature.
- MBP - Medium Back Pressure - Average evaporation temperature.
- HBP - High Back Pressure (High Back Pressure) - High evaporation temperature.
Depending on the compressor model, its application may extend from the LBP to the BPH classification (see table below).
Example of Application
-35ºC through -10ºC
Freezers & Refrigerators
-35ºC through -5ºC
Commercial Display Counters
and Drinking Fountains
-5ºC through +15ºC
and Drinking Fountains
When choosing a replacement model, it is very important to check what the original compressor was. As you know, the operation conditions of the compressor can vary with each project. Thus, there may be drinking fountains that need a BPH compressor while others use an L/MBP.
Check other Embraco compressors, divided by application: