Achieve Optimal Chiller Performance in Schools

Achieve Optimal Chiller Performance in Schools

Proper seasonal startup and shutdown procedures, along with a regular maintenance program, help to ensure that a chiller operates dependably and efficiently.  This results in reduced operating costs and improved occupant comfort throughout its life cycle.

 

SEASONAL STARTUP

A seasonal startup ensures that a chiller will operate reliably and efficiently throughout the upcoming cooling season.   It is beneficial to schedule a consistent time each year of operation to confirm that a machine is operating in an optimal manner and make adjustments as needed, even in warmer climates where traditional seasonal startups and shutdowns are not performed.  Follow these useful tips to ensure a seamless startup process.

  1. Prior to performing a seasonal startup, it is important to verify that the chilled and condenser water valves are in their proper operating positions. Only then should the cooling tower and heat exchanger(s) be filled. In addition, water treatment must be in place and operational to minimize the potential of scaling and corrosion.
  2. Check the oil sump and/or compressor oil levels using the factory-installed sight glass(es) and, where applicable, be certain the oil return system is operating properly.
  3. Oil filters should be replaced per the manufacturer’s recommendations to ensure that particulate-free oil is being supplied at all times to the compressor.
  4. Review the control panel for proper operation and check system pressures and temperatures to be certain the chiller is running in an optimal fashion.
  5. Conduct a vibration analysis at full-load conditions. This analysis should be performed at least annually to ensure that both the compressor and motor are in good working condition.
  6. Make sure that a proper load is present on a chiller during seasonal startups to more accurately validate chiller performance.

 

IMPORTANCE OF CHILLER SHUTDOWNS

The successful startup assumes the chiller was shut down properly and in a controlled manner.  Follow these useful tips to ensure a seamless shutdown process.

  1. To begin the shutdown process, review the control panel functions for proper operation and evaluation of recorded fault histories. Maintenance and repairs should be performed on system components such as cooling towers, pumps, valves, etc.
  2. Verify proper operation of the oil or crankcase heater(s). These heaters must be energized for a given time period prior to startup to make sure that the refrigerant is separated from the oil. Oil and refrigerant analysis will help identify issues with oil viscosity, moisture, and acid in the refrigerant.
  3. Water bundles should be isolated and drained. Once draining is complete, the water side of the bundles should be checked (using a refrigerant leak detector) to make certain that no leaks are present in the tubes.  At the same time, a thorough leak check of the chiller should be conducted.
  4. Oil and/or grease moving parts, as recommended by the manufacturer, and tighten all electrical connections.
  5. Clean the heat exchangers and condenser coils. Water boxes should be removed and the tubes brush cleaned. After cleaning, bundles need to be dried to prevent corrosion during the storage period and the water boxes reinstalled. Perform an eddy current test (where applicable) prior to reinstalling the water boxes to ensure that no corrosion/tube wear is present that could compromise the reliability of the unit. Condenser coils (air cooled equipment) should be washed in a manner that will not cause fin damage (refer to specific manufacturer instructions for details).
  6. Tag the chiller as out-of-service and take an inventory of emergency spare parts, replenishing them as necessary.

 

PARTNERING WITH THE RIGHT TECHNICIAN

When selecting a technician, be certain to choose someone who is experienced in servicing the type of chiller in your facility. A trained technician who is familiar with the chiller can use a chiller startup to make recommendations that will reduce energy costs and improve plant operation.  Where plants include multiple chillers, a technician might recommend changing the sequencing of the units so that they operate in a more efficient and reliable manner. In the case of an oversized chiller, recommendations can also be made to modify a unit and/or its control settings to help optimize its operation at light load conditions.

Using the services of a qualified technician delivers several important benefits, including improved chiller performance and reliability, minimized downtime, potential energy savings of 30% or more, maximum equipment life, minimal repair and service costs, and a greater return on capital equipment investment.

 

*Adapted from “Chiller Startup & Shutdown: Worth Doing Right” by Rick Nadeau, P.E.

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