Presentation on theme: "General System Maintenance BUS 4 COMPONENT FLOW.PPT"— Presentation transcript:
1General System Maintenance BUS 4 COMPONENT FLOW.PPT
2Refrigerant Oils - Bus Mineral Alkyl-Benzene Polyol-Ester (POE) Petroleum based oil for CFC refrigerants.Alkyl-BenzeneSynthetic 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.
3Checking Refrigerant Charge - Small Bus Systems System RunningHead Pressure Up150 PSIG Minimum - R-134aCheck Liquid Line SightglassClear Glass or the Occasional Bubble
4Adding / Removing Refrigerant Adding Complete System ChargeLiquid at the Receiver TankAdding Partial System ChargeVapor at the Compressor Suction Service ValveRemoving RefrigerantRefrigerant Recovery Machine
5Checking Compressor Oil Level System RunningMust be “Fully Loaded” (6 Cylinders)Head Pressure Up150 PSIG Minimum - R-134a250 PSIG Minimum - R-22Check Compressor SightglassBottom of glass to 1/2 - NEW 05G & 05KBottom of glass to 1/4 - OLD 05G
6Adding / Removing Oil Charge Adding Complete Oil ChargeIsolate Compressor and Add through compressor fill port.Adding Partial Oil ChargeRemoving Compressor OilIsolate Compressor and use drain plug.
7Compressor Test Procedure System RunningMust be “Fully Loaded” (6 Cylinders)Head Pressure Up250 PSIG Minimum - R-134a350 PSIG Minimum - R-22Note: Don’t let HPS Trip!Inability to maintain high discharge pressures may indicate internal problem.
8Know how to use all Refrigerant Recovery devices in your shop!! It’s the law under 608!
9Refrigerant RecoveryFollow All local environmental laws when referring to these instructions!
10Evacuation & 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.
11Evacuation & 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.
12Evacuation & 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 .
14Vacuum Pump A good Vacuum Pump Refrigerant Recovery Machine Two Stage PumpMinimum 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 MachineTo meet refrigerant handling regulations.
15Vacuum 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.
16Micron Gauge Digital Accuracy Designed to measure vacuum levels. Don’t use your Manifold Gauge Set - it’s not the right tool for the job!
17Why 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.
19Double Sweep MethodA 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.
20Double Sweep MethodWith 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.
21Double 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.
22Double Sweep MethodBreak 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.
23Double Sweep MethodRepeat: 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.
24Double Sweep MethodCheck 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.
26Weekly Maintenance Schedule Static Inspection (Coach Not Operating)Inspect Return Air FiltersInspect Coils for BlockageInspect All Refrigerant Fittings & HosesInspect All Coolant Lines & ConnectionsCheck Compressor Belt TensionCheck All Compressor Mount HardwareCheck All Electrical ConnectorsRecord Vehicle Information and Findings
27Weekly Maintenance Schedule Running Inspection (Coach in Operation)Check Refrigerant ChargeCheck Compressor Oil ChargeInspect Condenser, Evaporator and Driver’s Unit Motor Operation (Noise / Vibration)Check Coolant Circulating Pump OperationCheck Return Air Thermostat OperationRecord All Findings
28Yearly Maintenance Schedule Static Inspection (Coach Not Operating)Perform All Weekly InspectionsInspect Compressor Clutch for Excessive WearInspect the Compressor Clutch Air GapInspect Compressor Drive Belts for WearInspect Condenser and Evaporator Motor BrushesRecord Vehicle Information and Findings
29Yearly Maintenance Schedule Running Inspection (Coach Operating)Perform All Weekly InspectionsRun System and Record Pressures and TempsCheck Compressor Unloader OperationCheck Condenser Fan Speed SwitchCheck Low Pressure Cut Out SwitchCheck Condenser and Evaporator Motor Amp Draw and RPM at High and Low SpeedRecord All Findings.
30Common Problems Compressor Iced Superheat Setting is Too Low TXV Bulb is Poorly InstalledLocation / Contact / SecuredTXV Bulb is Poorly InsulatedLight Load from the CoachExcessive Compressor Oil in System
31Common Problems Frosted Evaporator Superheat Setting is Too Low Insufficient Air Across CoilDirty Return Air FiltersDirty Evaporator CoilMotor Down
32Common Problems High Head Pressure System Over Charged with RefrigerantInsufficient Air Across the CoilDirty Condenser ScreenDirty Condenser CoilMotor DownIncorrect Fan RotationAir in the System
33Common Problems High Suction Pressure Low Suction Pressure Blown Head GasketStuck UnloaderLow Suction PressureSystem Under Charged with RefrigerantFilter Drier PluggedBroken TXV Bulb / CapillarySuperheat Setting is Too Low
34Common Problems Low Suction Pressure (con’t) Insufficient Air Flow Across CoilDirty Return Air FiltersDirty Evaporator CoilMotor DownRestricted Supply Air DuctworkRestriction in Low Side Piping