Application Considerations

Condenser Water Limitations

Trane Series R ^® chillers start and operate satisfactorily over a range of load conditions with controlled entering condenser water temperature. Reducing the condenser water temperature is an effective method of lowering power input required. The leaving chilled water temperature and the percent of load have the most direct impact on the optimum condenser water temperature. In general, continuous machine operation with entering condenser water temperature below 55 F is not recommended.

The minimum acceptable water temperature entering the condenser is 15 F above the water temperature leaving the evaporator. When the entering condenser water temperature is expected to drop below 55 F, it is recommended that some form of condenser water temperature control be used to assure optimum machine performance. From a system perspective, improved chiller efficiency may be offset by increased tower fan and pumping costs. In order to achieve system optimization, each subsystem must be operated in the most efficient manner possible while continuing to satisfy the current building load.

Short Evaporator Water Loops

The proper location of the chilled water temperature control sensor is in the supply (outlet) water. This location allows the building to act as a buffer and assures a slowly changing return water temperature. If there is not a sufficient volume of water in the system to provide an adequate buffer, temperature control can be lost, resulting in erratic system operation and excessive compressor cycling. A short water loop has the same effect as attempting to control from the building return water.

As a guideline, ensure the volume of water in the evaporator loop equals or exceeds two times the evaporator flow rate. For a rapidly changing load profile, the amount of volume should be increased.

To prevent the effect of a short water loop, the following item should be given consideration:

A storage tank or larger header pipe to increase the volume of water in the system and , therefore, reduce the rate of change of the return water temperature.

Water Treatment

The use of untreated or improperly treated water in chillers may result in scaling, erosion, corrosion and algae or slime buildup. It is recommended that the services of a qualified water treatment specialist be engaged to determine what treatment, if any, is advisable. The Trane Company assumes no responsibility for the results of untreated or improperly treated water.

Water Pumps

Avoid specifying or using 3600 rpm condenser water and chilled water pumps. Such pumps may operate with objectionable noises and vibrations. In addition, a low frequency beat may occur due to the slight difference in operating rpm between water pumps and Series R chiller motors. Where noise and vibration-free operation are important, The Trane Company encourages the use of 1750 rpm pumps.