Trane SYS-APM001-EN manual Guidelines for system efficiency monitoring, Application Considerations

For a copy of ASHRAE Guideline 22 and other ASHRAE publications, visit the ASHRAE bookstore at www.ashrae.org/ bookstore.

SYS-APM001-EN

Application Considerations

Guidelines for system efficiency monitoring

ASHRAE Guideline 22 Instrumentation for Monitoring Central Chilled-Water Plant Efficiency6 was first published in June 2008. It states:

Guideline 22 was developed by ASHRAE to provide a source of information on the instrumentation and collection of data needed for monitoring the efficiency of an electric-motor-driven central chilled- water plant. A minimum level of instrumentation quality is established to ensure that the calculated results of chilled-water plant efficiency are reasonable. Several levels of instrumentation are developed so that the user of this guideline can select that level that suits the needs of each installation.

The basic purpose served by this guideline is to enable the user to continuously monitor chilled-water plant efficiency in order to aid in the operation and improvement of that particular chilled-water plant, not to establish a level of efficiency for all chilled-water plants. Therefore, the effort here is to improve individual plant efficiencies and not to establish an absolute efficiency that would serve as a minimum standard for all chilled-water plants.

Guideline 22 includes a discussion of:

•types of sensors and data measurement devices

•calibration

•measurement resolution, accuracy, and uncertainty

•calculation methods

•example specification

•examples of measured long-term performance

Guideline 22 recommends tracking and archiving the following over the life of the plant, in addition to normal equipment operating trends. The ability to obtain this information is dependent on the instrumentation and data measurement capabilities of the system.

1Average day’s outdoor air temperature (obtain the outside air temperature every 30 minutes and find the average of these samples each day)

2Day’s high temperature

3Day’s low temperature

4Day’s high wet-bulb temperature (calculate from temperature and enthalpy)

5Chilled-water supply temperature (average, max and min if chilled-water temperature is not fixed)

6Total ton-hours (kWh) production of chilled water for the day

7Total kWh power input for each component for the day

8Average kW/ton (COP) for the plant for the day

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