Application data (cont)
Consider adding additional piping and isolation valves to isolate each chiller to allow for service on the machine, and still allow for partial capacity from the other chiller.
Even if evaporators are piped in series, parallel con- denser piping should be considered on constant speed chillers to maximize capacity and efficiency while minimiz- ing condenser pressure drop and saturated condensing temperatures. If the condensers are piped in series, ensure that the leaving fluid temperature does not exceed 122 F (50 C) for standard units, or 140 F (60 C) for high con- densing or heat machine condensers.
Electric utility interests
Energy management — Use of energy management practices can significantly reduce operating costs, espe- cially during
Demand limiting (load shedding) — When a utility's demand for electricity exceeds a certain level, loads are
shed to keep electricity demand below a prescribed maxi- mum level. Typically, this happens on hot days when air conditioning is most needed. The energy management module (EMM) option can be added to accomplish this reduction. Demand may be limited on the unit by resetting water temperature, or by unloading the chiller to a given predetermined percentage of the load. Demand limit may also be driven by an external 4 to 20 mA signal. These fea- tures require a signal from an intelligent central control.
Duty cycling — Duty cycling will cycle an electrical load at regular intervals regardless of need. This reduces the electrical demand by "fooling" demand measuring devices. Duty cycling of the entire compressor is NOT recom- mended since motor windings and bearing life will suffer from constant cycling.
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