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HVAC: Chiller Maintenance From "Trade School" episode DTRS-212

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Figure B

Before he can service the chiller, Patrick must transfer the refrigerant from the chiller to a refrigerant conservation system (RCS) that consists of a compressor and a holding tank capable of storing large amounts of refrigerant (figure B). The use of this system prohibits the discharge of any refrigerant into the atmosphere.

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	Figure C
	Figure D
	Figure E
	Figure F
	Figure G
	Figure H
	Figure I

By configuring the valves on the RCS in a certain way, he starts by pulling the liquid refrigerant from the chiller to the holding tank. Next, he reconfigures the valves to transfer the vapor that remains in the chiller. As the vapor is moved into the RCS, it is condensed into a liquid.

The process of moving vapor into the tank is time consuming. Patrick takes this time to inspect the copper condenser tubes within the chiller. The condenser tubes are part of a water-flow cycle known as the condenser loop, which functions to expel heat from the chiller. Using a pneumatic ratchet, he removes two of the bolts from the access plate, which he replaces with longer guide bolts (figure C). The guide bolts support the plate while allowing Patrick to inspect the tubes. With the guide bolts in place, Patrick removes the remaining bolts. Finding the condenser tubes clean and in good working order (figure D), he bolts the access plate back into position. Dirty tubes would need to be scrubbed clean to allow for proper heat transfer.

The next day, with the refrigerant fully transferred into the RCS, Patrick checks the level of captured refrigerant with last year’s level and finds that there has been no decrease, indicating a well-sealed system. During the transfer, the RCS also created a deep vacuum within the chiller. Patrick neutralizes the vacuum by filling the chiller with dry nitrogen. If left in a vacuum state, air could rush into the opened chiller bringing with it moisture, which is undesirable as moisture and refrigerant combine to make a potentially damaging acid.

With the pressure stabilized, Patrick can access the inside components of the chiller. He begins by draining more than 15 gallons of oil into several plastic drums (figure E). Although the oil looks good, he bottles a sample to be sent off for analysis. With the oil removed, Patrick is now able to replace a series of oil filters. Aided by a flashlight, he also inspects the condition of the wiring in the crankcase and the heating element, which help to maintain the proper oil viscosity (figure F).

Next, Patrick inspects the metering device, which controls the flow of refrigerant. He uses a feeler gauge to make sure the clearances around the device are within tolerance (figure G).

Patrick replaces the filter that resides within the purge unit on top of the chiller. The purge unit removes any non-condensable material that may make its way into the chiller such as water or air.

Next, Patrick tests several safety features. Each test simulates a component failure and should trip a loud alarm. This helps to ensure that the chiller won’t be severely damaged in the event of a problem.

Patrick’s work inside the chiller is done. To make sure it is properly sealed, he performs a leak test (figure H). He pumps a mixture of dry nitrogen and a trace amount of refrigerant into the chiller, then runs a leak detector over every seal and joint on the chiller, listening for any alarms. The leak detector can detect even the slightest amount of refrigerant. After finding no leaks, Patrick releases the test gas and any residual air into a well-ventilated area using a vacuum pump (figure I).

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