Thermo Products 30, OPB (24, 36)- 80 service manual Evaporator Superheat

All installations and services must be performed by qualified service personnel.

5.Evaporator Superheat:

Before taking a superheat measurement allow the system to stabilize for 15 minutes under continuous operation. To measure superheat at the evaporator, a suction pressure reading at the outlet of the evaporator would be desirable. Since most residential cooling systems (including Thermo Pride evaporators) do not provide a test port (sometimes referred to as a Schraeder port) at the evaporator, the suction pressure must be read at the suction inlet to the compressor. Typically, it would be necessary to compensate for the pressure drop through the line connecting the evaporator and the compressor. However, due to the close proximity of these components, the pressure drop will be small and can be neglected. A good resistive-type thermometer or thermocouple-based sensor should be used to measure the suction line temperature exiting the evaporator. On evaporators using thermal expansion valves, read the temperature directly under the expansion bulb, located on the side of the suction line exiting the evaporator.

Measure refrigerant temperature at the 2:00 or 10:00 positions on the outer surface of the evaporator suction tube. Wrap the thermometer or thermocouple with a rag, or insulation, to insure system airflow does not influence the temperature readings.

Refer to Example 3, in Appendix B: Calculations of this manual, for a sample calculation of how to figure the degree of superheat for the evaporator. In general, Thermo Pride recommends an operating evaporator superheat of between 5° and 12°F.

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