general system maintenance bus 4 component flow.ppt bus 4 component flow.ppt

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General System Maintenance BUS 4 COMPONENT FLOW.PPT

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Page 1: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

General System Maintenance

BUS 4 COMPONENT FLOW.PPT

Page 2: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Refrigerant Oils - Bus

• Mineral– 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.

Page 3: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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

Page 4: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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

Page 5: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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

Page 6: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Adding / Removing Oil Charge

• Adding Complete Oil Charge– Isolate Compressor and Add through

compressor fill port.• Adding Partial Oil Charge

– Isolate Compressor and Add through compressor fill port.

• Removing Compressor Oil– Isolate Compressor and use drain plug.

Page 7: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 8: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Refrigerant Recovery

Know how to use all Refrigerant Recovery devices in your shop!!

It’s the law under 608!

Page 9: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Refrigerant Recovery

Follow All local environmental laws

when referring to these instructions!

Page 10: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 11: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 12: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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 .

Page 13: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Evacuation & Dehydration Tools

Page 14: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Vacuum Pump

• A good Vacuum Pump– 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.

Page 15: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 16: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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!

Page 17: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 18: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Evacuation & Dehydration Procedure

Triple Evacuation / Double Sweep Method

Page 19: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 20: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 21: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 22: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 23: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 24: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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.

Page 25: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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

Page 26: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Common Problems

• Frosted Evaporator– Superheat Setting is Too Low– Insufficient Air Across Coil

• Dirty Return Air Filters• Dirty Evaporator Coil• Motor Down

Page 27: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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

Page 28: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

Common Problems

• High 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

Page 29: General System Maintenance BUS 4 COMPONENT FLOW.PPT BUS 4 COMPONENT FLOW.PPT

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