Compressor Hot Gas Bypass (HGBP) heating water

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When microprocessor set point (SP1,SP2) is set below 45F, the chiller runs constant and appears to be heating water rather than cooling. Gylcol freeze protection may have been also added to the system.

All Legacy Chillers are tested and set up at the time they leave the factory to run water only. This is done to protect the chiller from freezing should a user drop the SP set point(s) below 45F prior to adding glycol freeze protection to the system.

When the SP set point(s) are programmed below 45F without adding glycol and setting the chiller up to run glycol the chillers HOT GAS BYPASS (HGBP) system will attempt to maintain approximately 54 PSI by bypassing HOT compressor discharge gas into the chillers evaporator. Under some operating conditions this (HGBP) can cause the chiller loop to heat and not cool.

If your process requires running your chiller loop colder than 45F, the proper concentration of glycol must be added to your system. When glycol is added to any chiller adjustments must be made to: The LP safety trip point(s), HGBP deployment pressure, low flow differential pressure switch and in some cases the TXV superheat settings.

See KB article “Glycol – Adding to chiller loop” for a step-by-step procedure on how to set your chiller up to run gycol.

All chiller models

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