Chiller surge occurs when refrigerant rushes backwards from the condenser to the compressor, causing serious damage to the system. As a result, it begins to flow backwards through the discharge line and into the compressor. Because the compressor's purpose is to pump refrigerant into the discharge line and into the condenser, it will continue to revolve. The refrigerant will flow back through the impeller blades and out through the suction line into the evaporator since the pressure is already too high.
The differential between condenser and evaporator refrigerant pressures determines the maximum lift (head pressure) of each chiller system. The difference between the leaving chilled-water temperature (LCHWT) and the incoming condenser-water temperature can also be used to determine lift (ECWT). If the differential rises above the pumping capability of the system, refrigerant will flow backward via the compressor wheel every few seconds. The refrigerant surges forward again as pressure rises in the compressor, and the cycle repeats. The thrust assembly, bearings, and gearbox may be damaged, and the safety disc may burst or the relief valve may blow. Surge is distinguished by a loud, distinct sound that has been compared to an elephant's screech or a surging jet engine, as well as a change in compressor amperage.
Chillers are built to satisfy specific system specifications and operating circumstances. A well selected chiller will not spike with proper maintenance and operation within design purpose. Surges can occur as a result of changes in operating conditions, especially when the load is low. Maintenance difficulties like clogged tubes, low refrigerant charge, or non-condensables in the refrigerant might cause a surge. Poor regulation of water flow rates and condenser water temperatures can also cause it. With hot gas bypass or VFDs, low load (surge) difficulties can be prevented or remedied.
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