Traditionally, water chillers have been treated simply as a plant service required by the manufacturing process, like electrical power. Unfortunately, water chillers are more complex than simply opening a water faucet or turning on a switch. They are self-contained electromechanical devices that include compressors, controls, refrigeration systems, pumps, piping and wiring. Any fault in a component can render a chiller inoperative and stop production, causing lost profit and a diminished return on investment. Even batch production processes (for example, batch cooling of cosmetics or pharmaceuticals) can lose a production run if a chiller fails to operate "on cue" for the required cooling cycle.
While the majority of industrial water chillers are dependable machines, additional redundant measures are required if any malfunction jeopardizes production and profitability. In any standard chiller, a refrigerant leak in the evaporator, condenser or piping will stop production for hours or even days. The same is true if the refrigeration compressor breaks a valve or suffers a burnt-out motor.
Questions to ask when considering whether a multicircuit redundant chiller is necessary include:
- If my manufacturing process chiller fails for any reason, what is the cost of lost production, sales and profit per hour? per shift? per day?
- How much does it cost to repair or replace the chiller on an emergency basis (including nights or weekends)?
- How much is a rental chiller (including mandatory minimum rental time, delivery and installation charges)?
Additional redundancy can be obtained by selecting an oversized four-circuit chiller in which any three circuits can handle the total cooling load. In this case, even with one circuit down, a site repair can be implemented while the remaining three circuits handle the total load. Modern microprocessor controls can rotate the compressor circuits automatically, based on run time, to equalize individual component wear factors.
An essential component of a multicircuit redundant chiller is the inclusion of individual power disconnects or manual circuit breakers for each compressor and pump. In this way, any major electrical component can be isolated, repaired or replaced while the chiller is still operational, and production can continue without a hitch.In the past, electromechanical controls have been considered simpler for a production or maintenance operator to troubleshoot or repair, but these controls are limited in capability -- especially for alarms and remote control or remote monitoring. The latest generation of plug-in microprocessor controllers is designed to be replaced easily and quickly in the event of any malfunction. These controllers are available in modular plastic enclosures with DIN rail clip-on mounting and plug-in wiring terminals, making complete replacement possible in minutes.
Standard microprocessor controls should offer the following features:
- Push-button chilled water temperature adjustment.
- LCD display of chilled water temperature, critical functions and alarms.
- Local visible and audible alarms for all critical functions.
- Serial port for remote monitoring or control via RS232 or RS485.
- World Wide Web connection port.
Process chillers should be considered an integral part of continuous production equipment for all critical applications. They should be designed and built for redundant operation if the chiller downtime cost is prohibitive from a lost production standpoint. It can be a costly mistake to consider chilled water as a simple factory service without first making provisions to keep it flowing.