The purpose of this maintenance standard procedure is to establish guidelines for the preventive maintenance of Package Type Air-conditioning units.
This pm procedure will also serve as guiding document for newly hired employees in the facility management or maintenance department who will be dealing with this type of air-conditioning unit.
Scope of this standard covers all Package Type Air-conditioning units which are under the A/C Maintenance Contract for any kind of the projects.
It is the responsibility of the A/C Technician to conduct the correct preventive maintenance of Package Type Air-conditioning units to prevent system from breakdown, thus providing the specified room temperature. He should be competent enough to conduct the activity to avoid any damage and to provide the proper result. The Supervisor and the Site Engineer should assure that this maintenance procedure will be followed.
Monthly Maintenance of Packaged Type AC Unit
Check the condition of the Condenser Coil. If it still clean, extend the frequency of cleaning to next month. If not, perform the following maintenance procedure:
Prior to the work, wear safety shoes, gloves and goggles.
Prepare screw driver, jet pump, chemical cleaning agent (if applicable) multi-meter and adjustable wrench.
Switch OFF the Package Type A/C Unit.
Switch OFF the isolator or circuit breaker supplying the unit.
Pull-out the air filter and clean. Let the filter dry before re-placing.
Check the evaporator coil and v-belt condition.
Replace v-belt if found damage.
Clean the condenser coil of the unit.
Set-up the pressure washer by tapping it to a water supply and connecting it to the correct power source.
Dilute the chemical cleaning agent to a container of water. Apply the diluted solution to the condenser by pouring it along the fins.
Wait for 10 minutes so that the chemical can be absorbed inside the coil.
Rinse the coil with water and slowly work the spray up and down the fins.
Direct the spray nozzle so that it is parallel to the fins. Do not spray at an angle to the fins because they could be bent and may cause damage to the coil.
Let the water drip and dry all components before starting the unit.
Start-up the unit.
Annual Maintenance of Packaged Type AC Unit
Prior to the work, wear safety shoes, gloves and goggles. Prepare clamp ammeter, jet pump, chemical cleaning agent and screw driver etc.
Compressor Annual Checking
- Change oil and oil filter. Drain the oil by removing the nut located below the compressor oil sump. Remove the oil filter and change with a new one. Charge new refrigerant oil using oil pump.
- Clean the crankcase sump with dampened cloth.
- Check the operation of the crankcase heater; replace if found defective.
- Replace liquid line filter drier core or shell type filter.
- Check unloading mechanism where applicable.
- Check suction and discharge pressure reading. Suction pressure should be 60 – 69 psi while discharge pressure should be 250 – 270 psi. Charge additional refrigerant if needed.
- Check oil pressure using gauge manifold.
- Overhaul and replace any defective parts if necessary.
- Check anti-vibration mounting; replace if found any defects.
- Check seals for any refrigerant leaks; replace if found any.
- Check for undue noise and vibration. Rectify if found any.
- Open the terminal box of the compressor motor. Clean and check for loose terminals and presence of burns. Conduct insulation test resistance on the motor winding.
Condenser Fan and Motor Maintenance
- Clean condenser coil by using approved chemical and by jet pump.
- Dismantle condenser fan blades. Check for cracks and defects; replace if found any. Clean and paint all condenser fan blades.
- Check insulation resistance of motor winding by using a multi-meter. Get line to line and line to ground resistance reading.
PM of Evaporator and Fan Motor
- Clean blower and blower housing.
- Check all fan shears and pulley.
- Fan motor bearing to be lubricated with approved bearing greased if grease port is available. Replace bearing if found to be defective.
- Pillow block bearing to be lubricated using approved grease. Replace bearing if found to be defective. Check tightness of pillow block mounting.
- Check fan shaft surface. Pull-out and re-build if scratches are evident.
- Check fan belt for damage. Replace if found damage.
- Check driver alignment and adjust deflection if found too tight or too loose.
- Check for any undue noise and vibration.
- Conduct insulation test resistance of motor winding. Conduct line to line and line to ground resistance checking.
- Check and tighten all terminals.
- Checked anti-vibration mounting of the compressor. Replace if found defective.
- Checked for damage sound linear insulator. Replace if found any damage.
Cooling Coil and Drain System Checking and Maintenance
Check and clean cooling coil with approved chemical.
Clean return air filter and fresh air filter if available. Dry the filter before replacing.
Check electric heater. Replace if found defective.
Check and clean condensate tray. Scrape and paint rusted portion of the tray.
Check and de-clogged drain line.
Control and Safety Devices Checking
Check solenoid valves for proper operation. Replace if found defective.
Check H.P. cut-out switch for proper function. Replace if found defective.
Check L.P. cut-out switch for proper function. Replace if found defective.
Check Oil Differential Pressure Switch. Repair or replace if found defective.
Check pressure relief valve where applicable.
Check expansion valve for proper function.
Check all thermostats for proper function.
Check air flow switch for proper function if available.
Control Panel and Side Panel Checking
Clean and check all contactors for possible defects. Replace if found any.
Check timer relay and delay timer if available.
Check overloads, transformers and fuses. Replace if found defective.
Check and tighten all terminals. Use contact cleaner (CRC) if available.
Clean inside and outside surface of the control panel.
Check operation of isolators for proper function. Clean inside and outside of the isolator unit.
Air Ducts Checking
Check flexible connection condition.
Check for damage sound linear insulation. Replace if found any defects.
Check for any air leakage.
Check fiber glass type insulation for any damage. Replace if found any.
All ducts to be wrapped with canvas cloth and to be covered with two coats of weather proof paint.
Check and clean supply and return grills.
Check operation of duct heaters for proper function. Repair or replace if found defective.
Check variable control damper operation where applicable.
Check splitter damper for proper function.
Check Fire Damper for proper function where applicable.
Replace damage and missing hangers, bracket and supports. Paint rusted portion of the ducting supports.
General Points
Scrape and paint rusted portion of the package unit using weather proof paint.
Attachment – Preventive Maintenance Checklist for Package Type A/C Units.
