Carrier 69NT40-541-500 Operation And Service Manual
Also see for 69NT40-541-300: Operation and service
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Contents
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T-363 7–247.16.1 Checking SuperheatNOTEProper superheat measurement should be completed at -18°C (0°F) container box temperature wherepossible.a. Open the upper right (EFM#1) access panel (see Figure 3.1) to expose the expansion valve.b. Attach a temperature sensor near the expansion valve bulb and insulate. Make sure the suction line is clean and thatfirm contact is made with the sensor.c. Connect an accurate gauge to the service port directly upstream of the suction modulating valve.d. Set the temperature set point to -18°C (0°F) and run unit until conditions stabilize.e. The readings may cycle from a high to a low reading. Take readings of temperature and pressure every three to fiveminutes for a total of 5 or 6 readings.f. From the temperature/pressure chart (Table 7–6), determine the saturation temperature corresponding tothe evaporator outlet test pressures at the suction modulation valve.g. Subtract the saturation temperatures in step f from the temperatures measured in step e. The difference isthe superheat of the suction gas. Determine the average superheat. It should be 4.5 to 6.7°C (8 to 12°F).7.16.2 TXV ReplacementNOTES1. The TXV is a hermetic valve, it does not have adjustable superheat (See Figure 7.20).2. All connections on the hermetic TXV are bi-metallic, copper on the inside and stainless on the outside.3. All joints on the hermetic TXV (inlet, outlet and equalizer lines) are brazed.4. Bi-metallic connections heat up very quickly.Figure 7.20 Thermostatic Expansion Valve1. Hermetic Thermostatic Expansion Valve2. Non-adjustable Superheat Stem3. Equalizer Connection4. Inlet Connection5. Outlet Connection6. Hermetic Expansion Valve Bulb- - - - -a. Removing the TXV:1. Pump down the unit per Section 7.4.2. If TXV replacement is to be performed from the front of the unit, open the upper right (EFM#1) access panel(see Figure 3.1) to remove evaporator fan motor.3. Remove cushion clamp that secures the valve body to the bracket.4. Unbraze the equalizer connection (1/4”), the outlet connection (5/8”), and then the inlet connection (3/8”). SeeFigure 7.22. Be careful to protect the insulation on the heaters and their wires.5. Open the insulation flap. Flap is secured with Velcro (Item 3, Figure 7.21).6. Loosen the thumb screw and slide the bulb, out by pulling it towards the front of the unit.123456 |
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