Guide to Preventive Maintenance Procedure for Central Air Conditioning Systems for Building Application

Basically, performing a preventive maintenance on a centralized air conditioning system in buildings is not a do-it-yourself task. This requires skills and hard work for most of the member of the maintenance department. Breakdowns would surely mean discomfort and above all “blame it to the maintenance people” idea. To avoid this, a schematic procedure should be provided and step-by-step task should be followed by all members of the maintenance group.

With this, I have laid down step-by-steps procedure of doing maintenance task for centralized air conditioning systems. More important is the frequency of performing this task which is very much essential for all centralized air conditioning systems. This guide will help supervisors in drafting a maintenance procedure or simply guide technicians doing the job.

Note that each maintenance task is arranged on a step-by-step procedure in order for the reader to easily follow each task.

1.0 Maintenance of Chiller Units

1.1. Swabbing of Condenser Shell and Tubes of Chillers units.

1.1.1 Close the isolation valve of the chiller condensing unit and drain the water inside the condensing unit through the drain port or blow down valve.

1.1.2 Chemical de-scaler shall be circulated to the condenser tubes and shell using a chemical pump through the ports provided for this purpose in the chiller unit. In order to dissolved, lossen and removed hardened residue and scales stuck on inside the tubes, it is important that the chemical de-scaler shall be circulated to the condensing unit for at least 3 hrs prior the actual draining.

1.1.3 Drain the chemical de-scaler and remove the shell at each end of the condensing unit.

1.1.4 Work a round nylon or brass bristled brush (attached to a rod) in and out of each end of the condenser water tubes to loosen the sludge).

1.1.5 Thoroughly flush the condenser water tubes with clean water and install the condensing unit shell at each end.

1.1.6 Contaminated water and waste chemical from this procedure shall be contained and disposed properly.

1.1.7 Implementation of this procedure shall be based on the assessment and recorded operating parameters of your central air conditioning unit.

1.2 Swabbing of Evaporator Shell and Tubes of Chiller Units.

1.2.1 Use the same cleaning method discussed in procedure 1.1 above. Schedule and frequency of implementation of this procedure shall be based on the assessment and recorded operating parameters of your central air conditioning unit.

1.3 Replacement of Gas Pump and Main Oil Filter of Trane Chiller

1.3.1 Stop the Chiller unit and close the manual service valves located before and after the filters.

1.3.2 Relieve the pressure from the hydraulic line through the ¼” Schrader valve located between the ball valves and the oil filter.

1.3.3 Use strap wrench to break loose the nut that secures the oil filter element to the filter manifold.

1.3.4 Turn the nut clockwise until the filter element detaches from the manifold.

1.3.5 Replace the filter element and re-install the new filter element to the filter manifold.

1.3.6 Connect manifold gauge to the oil charging valve and vacuum the filter element and manifold to -30 in Hg.

1.3.7 Charge the oil line back with the amount of oil removed.

1.3.8 Open the isolation valves to the oil supply system.

1.3.9 Waste and contaminated oil from this procedure shall be contained and disposed properly.

1.3.10 This procedure shall be done to gas pump filter and main oil filter of Trane chiller units annually.

1.4 Inspection / Cleaning of Chiller Casing

1.4.1 Ocular inspection of chiller casing shall be conducted on all Chiller units. Any sign of oil / water leaks and damaged part shall be noted and provided with necessary corrective action.

1.4.2 This procedure shall be conducted monthly on all Chiller units.

1.5 Chiller Oil Analysis

1.5.1 Oil Analysis shall be conducted to all Trane chillers annually by a qualified Service Engineer / Technician.

1.6 Oil Replacement Procedure for Trane Chiller units

1.6.1 Remove the refrigerant from the chiller unit and contain the refrigerant to an empty cylinder tank and by means of a vacuum pump until the refrigerant pressure drops to 10 psig. Then stop the chiller unit.

1.6.2 Connect a hose to the oil sump drain valve.

1.6.3 Open the drain valve and allow the desired amount of oil to flow into an empty container provided for the used oil. Then close the charging valve.

1.6.4 Measure the exact amount of oil removed from the unit.

1.6.5 Locate the ¼” Schrader valve between the ball valve and oil filter.

1.6.6 Loosely connect oil pump to Schrader valve.

1.6.7 Open oil charging pump until oil appears at the charging valve connection and tighten the connection.

1.6.8 Close the ball valve just upstream of the Schrader valve connection to the oil pump this will allow the oil to travel through the oil lines to the compressor first rather than directly to the oil sump.

1.6.9 Energize the master oil solenoid. This will allow the oil to travel from the Schrader to the compressor. It takes approximately 2 gallons of oil to fill the lines.

1.6.10 After charging the first 2 gallons, de-energize the master solenoid.

1.6.11 Open the ball valve just upstream of the Schrader connected to the oil pump. This will allow the remainder of the charge to flow to the oil sump.

1.6.12 Charge the chiller unit with applicable refrigerant. Charging of refrigerant shall be done at an ambient temperature of not less than 35° C.

1.6.13 Used oil from this procedure shall be contained and disposed properly.

1.6.14 Implementation of this procedure shall be based on the result of the oil analysis conducted in procedure 1.5.

2.0 Maintenance of Cooling Tower

2.1 Cleaning of Cooling Tower Filters

2.1.1 Close the isolation valves of the cooling tower to be maintained.

2.1.2 Removed PVC Filler Materials inside the cooling tower carefully. If the condition of the PVC Filler Materials is not acceptable for re-use, immediate replacement shall be done.

2.1.3 Clean the PVC Filler materials using pressure washer until all dirt and mineral deposits are removed.

2.1.4 Re-install the PVC Filler material to the cooling tower.

2.1.5 Mandatory replacement of PVC Filler materials shall be done every 3 years.

2.1.6 This procedure shall be done on all cooling tower of chiller units semi-annually.

2.2 Cleaning / De-scaling of Cooling Tower

2.2.1 Stop the Cooling Tower and turn-off load breaker switch. Provide lockout tag out on load breaker switch.

2.2.2 Carefully remove the strainer from the suction line of the Cooling Tower and wash it with water thoroughly (if possible). If scale has already accumulated in the strainer, chemical de-scaler may be used.

2.2.3 Cleaning / De-scaling of Cooling Tower Strainer shall be conducted monthly on all Cooling Towers.

2.3 Gear Oil Level Inspection

2.3.1 Stop the Cooling Tower and turn-off load breaker switch. Provide lockout tag out on load breaker switch.

2.3.2 Check gear oil level through sight glass provided on the gear box. If gear oil is below the acceptable level as indicated in the sight glass, check casing for possible leaks and implement the necessary corrective action.

2.3.3 Re-fill the gear box with gear oil up to acceptable level.

2.3.4 This procedure shall be conducted monthly on all tower of the Trane Chiller.

2.4 Gear Oil Replacement

2.4.1 Stop the Cooling Tower and turn-off load breaker switch. Provide , provide Lock-out Tag-out warning system on load breaker switch.

2.4.2 Drain the Gear Oil form the gear box though the drain plug.

2.4.3 Re-fill the Gear box with appropriate Gear Oil up to acceptable level as indicated in the sight glass.

2.4.4 This procedure shall be implemented on all Cooling Tower of Trane Chiller semi-annually.

2.5 Inspection of Sprinkler Bearings, Fan Blades and Cooling Tower Casing

2.5.1 Stop the Cooling Tower and turn-off load breaker switch. For safety reasons, provide lock-out tag-out on load breaker switch.

2.5.2 Check Sprinkler Rotor Bearing. Lubricate or replace if necessary.

2.53 Check Fan Blades for damage and scale deposits. Clean / De-scale or Replace if necessary.

2.5.4 Check Cooling Tower casing for damage and scale deposit. Clean / De-scale or Repair if necessary.

2.5.5 This procedure be implemented on all Cooling Tower semi-annually.

3.0 Maintenance of Chilled and Condenser water Pump

3.1 Stop the Pump and turn-off load breaker switch. For safety reasons, provide Lock-out Tag-out warning system on load breaker switch.

3.2 Close isolation valves on the discharge and suction line.

3.3 Check alignment of motor against the water pump. Alignment shall be conducted if necessary.

3.4 Inspect Pump Mechanical / Packing seal for leaks. Replace Mechanical / Packing seal if necessary.

3.5 This procedure shall be conducted on all Chilled and Condenser water pumps on a monthly basis.

4.0 Cleaning of Chilled and Condenser Water In-line Strainers

4.1 Stop the chilled and condenser water pumps of the in-line strainers to be maintained and close the respective isolation valves at the suction and discharge of the pump.

4.2 Carefully remove the strainer from the pipe line and wash it with water thoroughly (if possible). If scale have already accumulated in the strainer chemical de-scaler may be used.

4.3 Re-install the strainer.

4.4 Waste chemical and contaminated water from this procedure shall be contained and disposed properly.

4.5 This procedure shall be conducted on all condenser water in-line strainers semi-annually. Like wise, this procedure shall be conducted on all evaporator water in-line strainers annually.

5.0 Maintenance of Air Handling Units

5.1 Cleaning of Cooling Coil

5.1.1 Stop the Air Handling Unit and turn off the load breaker switch.

5.1.2 Rinse the cooling coil with an approved chemical coil cleaner (30 liters max.) using pressurized chemical applicator and let the chemical work or penetrate for 15 min.

5.1.3 Rinse the cooling coil with clean water sufficient enough to remove all dirt in the coil.

5.1.4 Contaminated water from this procedure shall be contained and disposed properly.

5.1.5 This procedure shall be implemented on all Air Handling Units semiannually.

5.2 Cleaning of 50 microns pre-filters

5.2.1 Cleaning of 50 micron pre-filters shall be conducted on all Air Handling weekly. Clean water and neutral detergent shall be used for this procedure.

5.3 Inspection of Pillow Blocks / Bearings / Fan Belt Condition and Tension

5.3.1 Stop the Air Handling Unit and turn-off load breaker switch. For safety reasons, provide Lock-out Tag-out warning system on load breaker switch.

5.3.2 Check the condition of Pillow Blocks and Bearings. Replace / Lubricate if necessary.

5.3.3 Check alignment of fan pulley against motor pulley. Alignment shall be conducted if necessary.

5.3.4 Check Fan Belt condition and tension. Adjustment / Replacement shall be conducted if necessary.

5.3.5 This procedure shall be conducted monthly on all Air Handling Units.

5.4 Inspection of AHU Casing / Cooling Coil

5.4.1 Stop the Air Handling and turn-off load breaker switch. For safety reasons, provide Lock-out Tag-out warning system on load breaker switch.

5.4.2 Check Air Handling Unit casing for damage, corrosion, and cleanliness. Clean / Repaint / Repair shall be conducted if necessary.

5.4.3 This procedure shall be conducted on semi-annually on all Air Handling units.

6 Maintenance of Expansion Tank

6.1 Condition of Expansion Tank Float Valve shall be inspected for damage and float ball adjustment. Replace / Adjustment shall be conducted if necessary.

6.2 Expansion Tank casing shall be inspected for damage, corrosion and cleanliness. Clean / Repaint / Repair shall be conducted if necessary.

6.3 This procedure shall be conducted on Expansion Tank on monthly basis.