Chillers are a critical element in HVAC systems. Chillers take the heat out of the air and also are implemented in industrial settings to cool down equipment. Chillers often represent a plant's single largest electric load. But factor in fouled tubes, leaking refrigerant, or myriad other factors, and operating costs can quickly escalate by eight to 10%.

In this post we’ve provided an air cooled chiller maintenance checklist as it is the most common design. Operating chillers at their peak performance will save energy and maintenance costs.

1) Check the compressor oil level. This should be visible through the sight glass with the
machine running at full load. Let the compressor operate for 3 to 4 hours before adding any
oil. Check the oil level every 30 minutes. If the level does not reach the level indicated above,
contact a qualified refrigeration mechanic.
Caution, for units equipped with tandem or trios scroll compressors, the oil level must
be checked - and visible - while the compressors are stopped. The oil level with running
compressors is not relevant.
2) Overcharging with oil can be as dangerous to a compressor as a lack of oil. Before topping up,
contact a qualified technician. Only use oils recommended by the manufacturer.
3) Check the oil pressure.
4) The flow of liquid refrigerant through the sight glass should be steady and without bubbles.
Bubbles are a sign of a low charge, a possible leak, or of a restriction in the liquid line. Contact a
qualified technician.
5) Check operating pressures. If they are higher or lower than those recorded when the machine
was put into service.
6) Inspect the entire system so as to detect any eventual abnormality: noisy compressor, loose
casing panels, leaky pipes or juddering contacts.
7) Record temperatures, pressures, dates et times and any other observations in the service log.
8) Leak detection is recommended.

Inspect valves and piping. Clean the filters if necessary, clean the condenser tubes. Clean
the chilled water piping filters.
CAUTION: The chilled water circuit may be pressurized. Observe the usual precautions when
depressurizing the circuit before opening it. Failure to observe these rules could lead to
accidents and cause injury to service personnel.
2 )Clean any corroded surfaces and repaint them.
3) Inspect the chilled water circuit for any signs of leakage.
Check operation of the water circulating pump and its ancillaries.
Check the percentage of antifreeze in the chilled water circuit, top up as necessary (if antifreeze
is used).
4) Carry out all weekly maintenance duties. Every year, the first and last inspection will include
the seasonal shutdown procedure or the restarting procedure depending on the case. These
inspections should include the following operations:
* Check the contacts of motor contactors and control devices.
* Check the adjustment and operation of each control device.
* Conduct an oil analysis to determine the acidity. Record the results.
* Change the oil if necessary.
* Follow the recommendations given by LENNOX as concerns compressor oil (see the appropriate table).
* Conduct a refrigerant leak test.
* Check motor winding isolation.

Other operations may be necessary depending on the age and the number of hours
of operation of the installation.


Air cooled condensers :-

Clean the coils either with a vacuum cleaner, cold water, compressed air, or with a soft brush (non metallic). On units installed in a corrosive atmosphere, coil cleaning should be part of the regular maintenance program. On this type of installation, all dust gathered on the coils should be quickly removed by regular cleaning.

Multi-tube water cooled condensers :- 
Use a cylindrical brush to remove sludge and other substances in suspension inside the condenser tubes. Use a non corrosive solvent to remove scale deposits. The water circuit in the condenser is manufactured in steel and copper. A water treatment specialist, given the right information, will be able to recommend the right solvent for removing scale.
The equipment to be used for external water circulation, the quantity of solvent and the safety measures to be taken must be approved by the company supplying the cleaning products or by the company conducting these operations.

Oil for refrigeration equipment is clear and transparent. It keeps its color over a long period of operation. Given that a correctly designed and installed refrigeration system will operate without any problems, there is no need to replace the compressor oil even after a very long period of operation.

Oil that has become dark in color has been exposed to impurities in the refrigeration piping system or to excessive temperatures on the discharge side of the compressor, and this inevitably impairs the quality of the oil. Darkening of the color of the oil or degradation of its qualities can also be caused by the presence of humidity in the system. When the oil has changed color or has been degraded, it must be changed. In this event, before putting the unit back into service, the compressor and the refrigeration circuit will have to be evacuated.

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