Thermo King – Expansion Valve Check / Adjustment

Purpose: This check confirms the expansion valve setting and operation and enables the technician to make
adjustments if required.

NOTE: Perform low side pumpdown, compressor capacity test, controlled refrigerant level check, engine RPM, etc.

Repair as needed before continuing.

Expansion Valve Check / Adjustment Procedures
1. Examine and/or clean evaporator & condenser coils.
2. Install an accurate compound gauge in the equalizer line.
3. Install an accurate thermometer sensor beside the expansion valve feeler bulb and secure and insulate it.
4. Defrost the evaporator and stabilize the box temperature near 40 F (4 C).
5. Cover the condenser as needed to maintain discharge pressure as is normal for 100 F (38 C) ambient temperature.
6. Check the type of refrigerant in the unit and determine the recommended discharge pressure from the table on page 2.
7. Read the equalizer pressure and suction line temperature simultaneously. Make several readings approximately every 2 minutes.
8. Superheat should be between 6 F (-3 C) and 12 F (-7 C) at 0 F (-18 C) box temperature.

Calculate superheat according to the sample below.
22 F (-6 C) degrees = Suction Line Temperature
15 psig. = Equalizer Line Pressure
Convert equalizer line pressure to temperature using a pressure/temperature chart. 15 psig – 10 F (-12 C)
Superheat = 22 F – 10 F or 12 F degrees
= -6 C – (-12 C) or 6 C degrees