Trane TRG-TRC011-EN manual Equipment Rating Standards

period five

Application Considerations

notes

a refrigerant vapor detector to monitor refrigerant levels in the machinery room. When the detector measures refrigerant levels above those allowable, a building automation system is used to automatically shut down the combustion process. Due to the lower cost, many building owners employ exception (b) in machinery rooms that have direct-fired absorption chillers or boilers.

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◆Establish definitions, testing, and rating requirements

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◆Single- and double-effect absorption chillers

◆Indirect- and direct-fired absorption chillers

◆Water-and-lithium bromide solution

Figure 67

Equipment Rating Standards

The Air Conditioning & Refrigeration Institute (ARI) establishes rating standards for packaged HVAC equipment. The overall objective of ARI Standard 560 is to promote consistent rating of many types and sizes of absorption water chillers. It covers single-effect chillers operating on steam or a hot fluid, double-effect chillers operating on steam or a hot fluid, and direct-fired double-effect chillers operating on natural gas, oil, or liquid petroleum (LP). It pertains to chillers using water as the refrigerant and lithium bromide as the absorbent.

The standard rating conditions used for ARI rating represent typical design temperatures and flow rates for which water-cooled systems are designed. They are not suggestions for good design practice for a given system—they simply define a common rating point to aid comparisons. Trends toward improved system energy efficiency have changed some of the actual conditions for specific applications.

Impurities in the chilled- and cooling-water systems eventually deposit on evaporator, absorber, and condenser tube surfaces, impeding heat transfer. Catalogued performance data includes a fouling factor that accounts for this effect to more closely predict actual chiller performance.

Remember that the ARI rating is a standardized representation. Many chillers do not run at standard rating conditions. Performing a comprehensive energy analysis is still the best method of comparing the system operating cost difference between two chillers.

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