1. General System Maintenance BUS 4 COMPONENT FLOW.PPT

2. Refrigerant Oils - Bus Mineral Alkyl-Benzene Polyol-Ester (POE)
Petroleum based oil for CFC refrigerants.
Alkyl-Benzene
Synthetic oil similar to mineral for HCFC’s.
Polyol-Ester (POE)
Ester based oil for HFC refrigerants.
Poly-Alkylene-Glycol (PAG)
Glycol based oil for automotive applications.

3. Checking Refrigerant Charge - Small Bus Systems
System Running
Head Pressure Up
150 PSIG Minimum - R-134a
Check Liquid Line Sightglass
Clear Glass or the Occasional Bubble

4. Adding / Removing Refrigerant
Adding Complete System Charge
Liquid at the Receiver Tank
Adding Partial System Charge
Vapor at the Compressor Suction Service Valve
Removing Refrigerant
Refrigerant Recovery Machine

5. Checking Compressor Oil Level
System Running
Must be “Fully Loaded” (6 Cylinders)
Head Pressure Up
150 PSIG Minimum - R-134a
250 PSIG Minimum - R-22
Check Compressor Sightglass
Bottom of glass to 1/2 - NEW 05G & 05K
Bottom of glass to 1/4 - OLD 05G

6. Adding / Removing Oil Charge
Adding Complete Oil Charge
Isolate Compressor and Add through compressor fill port.
Adding Partial Oil Charge
Removing Compressor Oil
Isolate Compressor and use drain plug.

7. Compressor Test Procedure
System Running
Must be “Fully Loaded” (6 Cylinders)
Head Pressure Up
250 PSIG Minimum - R-134a
350 PSIG Minimum - R-22
Note: Don’t let HPS Trip!
Inability to maintain high discharge pressures may indicate internal problem.

8. Know how to use all Refrigerant Recovery devices in your shop!!
It’s the law under 608!

9. Refrigerant Recovery
Follow All local environmental laws when referring to these instructions!

10. Evacuation & Dehydration
Moisture is the deadly enemy of any refrigeration or A/C system!
The presence of moisture causes many undesirable effects.
Non-condensibles = high discharge pressures.
Copper plating in the Compressor.
Formation of acids.
“Freezing-up” of TXV by free water.

11. Evacuation & Dehydration
Any time the system has been open to the atmosphere, it is necessary to properly evacuate and dehydrate the system.
Evacuation and dehydration will remove air and moisture form the system.
This will be done by using a pump that will lower the pressure of the system, which lowers the boiling point of water and turns water into vapor.

12. Evacuation & Dehydration
Only evacuate and dehydrate the system after a proper leak test has been done and all leaks have been repaired.
Keep ambient temperature above 60° F.
This will speed evaporation of moisture .
If the temperature is lower than 60° F., ice may form before moisture removal is complete .

13. Evacuation & Dehydration Tools

14. Vacuum Pump A good Vacuum Pump Refrigerant Recovery Machine
Two Stage Pump
Minimum capacity of 3 to 6 CFM.
The oil in the pump will trap some of the moisture from the refrigeration system.
You must keep the pump in top condition, change pump oil after a maximum of every three uses.
Refrigerant Recovery Machine
To meet refrigerant handling regulations.

15. Vacuum Hoses 3/8” ID Hoses are designed for vacuum pressures.
1/4” ID Hoses are designed for Positive Pressures.
Easier to pull vacuum on larger diameter.
Keep Hoses as short as possible.

16. Micron Gauge Digital Accuracy Designed to measure vacuum levels.
Don’t use your Manifold Gauge Set - it’s not the right tool for the job!

17. Why use a Micron Gauge?
To Insure all Moisture is Removed from the System during Dehydration!
The Compound Gauge of the Manifold Gauge Set is not designed to accurately measure vacuum.
Boiling Point of Water is dependant on the Pressure within the system.

18. Evacuation & Dehydration Procedure
Triple Evacuation / Double Sweep Method

19. Double Sweep Method
A procedure for completely evacuating and dehydrating a system that has been open to the atmosphere.
After repair and adequate leak check, connect the evacuation manifold, vacuum pump, hoses and micron gauge to the refrigerant recovery unit and the system.

20. Double Sweep Method
With the unit service valves back-seated, start the vacuum pump and draw the manifold and hoses into a very deep vacuum. Shut the vacuum pump off and see if the vacuum holds.
This is to check the setup for leaks. Repair all leaks detected.
Mid-seat the system service valves.

21. Double Sweep Method Open the vacuum pump and the thermistor valves.
Start the pump and evacuate to a system pressure of 2000 microns.
Close the vacuum pump and the thermistor valves.
Turn off the vacuum pump.

22. Double Sweep Method
Break the vacuum with dry nitrogen and raise the pressure to approximately 2 PSIG. Monitor the pressure with the compound gauge.
Release the nitrogen to atmosphere. The Dry Nitrogen will absorb moisture. This moisture will be removed during the release.

23. Double Sweep Method
Repeat: Vacuum to 2000 microns and Sweep with 2 PSIG of Dry Nitrogen.
After the second “Sweep”, change the filter drier (if you have not done so).
Evacuate to 500 microns.
Note: Evacuating the system below 500 microns on systems using open drive compressors may risk drawing air into the system past the shaft seal.

24. Double Sweep Method
Check to insure the vacuum holds. If the pressure continues to rise, it indicates a leak or more moisture in the system.
Charge the system with the proper amount of refrigerant using recommended charging procedures.
Run the system and verify system pressures.

25. Preventative Maintenance Schedule
Weekly Inspections
Yearly Inspections

26. Weekly Maintenance Schedule
Static Inspection (Coach Not Operating)
Inspect Return Air Filters
Inspect Coils for Blockage
Inspect All Refrigerant Fittings & Hoses
Inspect All Coolant Lines & Connections
Check Compressor Belt Tension
Check All Compressor Mount Hardware
Check All Electrical Connectors
Record Vehicle Information and Findings

27. Weekly Maintenance Schedule
Running Inspection (Coach in Operation)
Check Refrigerant Charge
Check Compressor Oil Charge
Inspect Condenser, Evaporator and Driver’s Unit Motor Operation (Noise / Vibration)
Check Coolant Circulating Pump Operation
Check Return Air Thermostat Operation
Record All Findings

28. Yearly Maintenance Schedule
Static Inspection (Coach Not Operating)
Perform All Weekly Inspections
Inspect Compressor Clutch for Excessive Wear
Inspect the Compressor Clutch Air Gap
Inspect Compressor Drive Belts for Wear
Inspect Condenser and Evaporator Motor Brushes
Record Vehicle Information and Findings

29. Yearly Maintenance Schedule
Running Inspection (Coach Operating)
Perform All Weekly Inspections
Run System and Record Pressures and Temps
Check Compressor Unloader Operation
Check Condenser Fan Speed Switch
Check Low Pressure Cut Out Switch
Check Condenser and Evaporator Motor Amp Draw and RPM at High and Low Speed
Record All Findings.

30. Common Problems Compressor Iced Superheat Setting is Too Low
TXV Bulb is Poorly Installed
Location / Contact / Secured
TXV Bulb is Poorly Insulated
Light Load from the Coach
Excessive Compressor Oil in System

31. Common Problems Frosted Evaporator Superheat Setting is Too Low
Insufficient Air Across Coil
Dirty Return Air Filters
Dirty Evaporator Coil
Motor Down

32. Common Problems High Head Pressure
System Over Charged with Refrigerant
Insufficient Air Across the Coil
Dirty Condenser Screen
Dirty Condenser Coil
Motor Down
Incorrect Fan Rotation
Air in the System

33. Common Problems High Suction Pressure Low Suction Pressure
Blown Head Gasket
Stuck Unloader
Low Suction Pressure
System Under Charged with Refrigerant
Filter Drier Plugged
Broken TXV Bulb / Capillary
Superheat Setting is Too Low

34. Common Problems Low Suction Pressure (con’t)
Insufficient Air Flow Across Coil
Dirty Return Air Filters
Dirty Evaporator Coil
Motor Down
Restricted Supply Air Ductwork
Restriction in Low Side Piping