1. Left Side Discharge Pressure Regulator
Remove Cap to Adjust Valve
Schrader Valve

2. Adjusting Discharge Pressure Regulating Valve
Unit must be on defrost for adjustment of setting
Proper setting for R404a is ~ 240 to 270 psig
Use 5/16 inch Allen wrench to adjust
CW rotation increases pressure, CCW decreases pressure
Replace cap after adjustment

3. Right Side Suction Pressure Regulator & Hot Gas Valve
Electrical connection to Solenoid of Valve
Hot Gas Valve
Remove cap to adjust suction pressure regulator valve
Electrical cable to compressor junction box

4. Adjusting Suction Pressure Regulating Valve
Box temp should be above 5 C
Setting should be ~ 30 to 35 psig for R404A
Use 5/16 inch Allen wrench to adjust
1 turn changes setting by 2.5 psig
CW rotation increases pressure, CCW decreases pressure
Run system 15 minutes to confirm setting
Be sure to replace cap

5. Filter Dryer & sight glass with protective cover To replace Filter Dryer:
Have new filter ready for installation
Perform Low Side Pump down, but make sure to have a slight positive presure
Loosen Bracket
Loosen flare nuts
Replace filter
Tighten flare nuts
Tighten bracket
Open liquid line hand valve

6. Liquid Line Sight Glass & Filter Dryer
Check for moisture in system
Observe color in sight glass
If yellow replace filter dryer and recycle the refrigerant
Run for 12 hours or until sight glass is green, and look for leaks on the suction side
If not green after 12 hours, replace filter dryer, recycle and look for leaks again

7. Hot Gas Solenoid Valve for Defrost
Solenoid of the Hot Gas valve
Hot Gas valve
When energized directs hot gas to the evaporator for evaporator coil defrosting
Suction pressure regulating valve

8. High Pressure Switches
If pressure too high switch opens and de-energizes compressor contactor coil
Right side compressor high pressure safety switch
Unscrew flare fitting to remove switch
Left side compressor high pressure safety switch
Loom removed to show switch wires

9. Compressor check With condenser contactor disconnected run unit
Discharge pressure should increase until high pressure switch opens
Close hand valve on receiver
Compressor should pump down to 15 – 20 inches Vacuum or lower
Check current on L1, L2 and L3; 7 to 12 Amps is OK

10. TXV Placement and Adjustment
TXV located in unit
Proper Bulb location
Tightly clamped to suction line
After it is properly located and clamped, bulb is wrapped with insulation (not shown)
Remember TXV is set at factory and should not need adjustment

11. Thermal Expansion Valve (TXV)
Sensing Bulb
Capillary line
Power Element
Liquid Line in
Line out to Distributor
Equalizer Line
Removable Cap for adjustment

12. TVX Adjustment is Seldom Required
Pull container down to -20 C
Remove cap from TX with adjustable wrench
Adjust superheat (SH) setting with refrigeration wrench
CCW reduces SH and CW increases SH
Do not adjust more than 1 turn
Let system run and settle out
It may take as much as 30 minutes for the system to balance after the adjustment
Replace cap

13. Detecting Blockage in Refrigeration System
Blockage is usually caused by dirt, moisture, or TXV power element loosing its charge
Blockage can be detected by lower than normal suction pressure and reduced capacity
When moisture in the system exceeds the capacity of the dryer to remove it, ice will form in the dryer. This causes a pressure drop and the liquid refrigerant will evaporate. There may be frost on the dryer and/or the liquid line leaving the dryer.
There will not always be frost visible, but the liquid into the dryer should be warm and the liquid out should be cold
Dirt or moisture may cause the TXV to stick in one position
Check this by watching the suction gauge to see if the TXV is modulating. It the suction pressure stays steady the TXV is stuck. The evaporator return air temp must be at -5 C or below to check this.
Check for frozen TXV
Shut unit down
Wait ~ 20 minutes for ice on TXV to melt
At start up unit operation should be normal, after running for awhile if the TXV again sticks and does not modulate, then the problem is moisture.
If after start up, unit operation has not changed it is most likely dirt in the system or the TXV element has lost its charge

14. Properly Adjusted TXV Conditions
Suction Line from Evaporator
Should be frost on suction line
Possible frost on suction service valve (not shown)
Little or no frost on end of bell
Oil sump should feel warm

15. Evaporator Coil with Temperature Probes
Hot Gas Defrost Line
Return Air temperature probe
Defrost temperature probe

16. Condenser Section with Grill removed
Condenser fan
Motor junction box
Coils

17. Evaporator Supply Air Discharge
Louvers removed to show supply air port
Evaporator fan pulls return air through evaporator coil
And blows it through this opening into the cargo area
Louvers prevent short cycling of supply air back into evaporator section

18. Liquid Receivers with Sight Glasses
Left Side Right Side

19. Fusible Plug and Purge Valve of Receiver
Hand Valve
Purge Valve from rear
Fusible Plug from rear

20. Removal of Non-Condensable Gasses
Existence of Non-Condensable Gasses is the major cause of high discharge pressure.
Air and Non-Condensable Gasses collect at the top of receiver
Refrigeration reclaim equipment must be connected to the purge valve on the receiver
Hose from reclaim equipment must be able to depress Schrader valve
Remove small amount of refrigerant through reclaim device
Observe discharge pressure for 5 minutes
Repeat until discharge pressure is normal, saturated discharge pressure should be 11 to 17 degrees C above the ambient
If discharge pressure fails to return to normal, reclaim refrigerant charge, pump system into a vacuum and recharge with refrigerant

21. Refrigerant Leak Testing
Check all joints and fittings
The preferred method for leak detection is use of an electronic leak detector
Leak testing with soap suds will reveal only larger leaks
Portable electronic leak detectors are usually used for field testing

22. Mega-Ohm Testing Purpose: test motor insulation with high Voltage DC
A Go-No-go proof test of motor insulation
Megger will produce voltage pulse and indicate pass or fail
Used to check compressor and fan motors
Three basic types: Hand crank, line operated and battery
Test Voltage:
Device rating up to 100 Vac – test voltage is 100 to 250 Vdc
Device rating 440 to 550 Vac – test voltage is 500 to 1000 Vdc
Device rating 2000 Vac – test voltage 1000 to 2500 Vdc
Caution: Never touch test leads during test and electrically isolate the motor being tested

23. Test Procedure Record nameplate information Select test voltage
To test insulation between lead and earth ground, connect 1 terminal to the lead and the other to a good earth ground
To test between a winding and frame, connect 1 terminal to the lead and 1 terminal to ground
Test L1, L2 and L3
For hand crank megger, turn at ~ 160 RPM
Megger will indicate pass or fail
Record test results, test every 8 to 12 months