| 摘要 |
To conserve energy in a large capacity refrigeration or air conditioning system, where liquid (usually water) is chilled by the system's evaporator and is then used to cool a building, the temperature setpoint of the chilled liquid leaving the evaporator may be reset upward from its desired level. Normally, if the temperature of the leaving chilled liquid falls below the setpoint by a fixed differential (such as 4 DEG F.) to a cut-out temperature, the system's compressor is shut down as a safety precaution to prevent freeze-ups. A nuisance compressor shutdown may be avoided when the setpoint is reset to a higher level (since the actual temperature of the leaving chilled liquid at that time may be at or below the desired setpoint and may be more than 4 DEG below the reset setpoint) by lowering the cut-out temperature to a fixed level substantially below the desired setpoint, such as down to 36 DEG F. By maintaining the cut-out temperature at its reset level for a limited time (for example, ten minutes), the refrigeration system will be allowed to stabilize at the higher reset setpoint, after which the cut-out temperature is re-established at its normal level of 4 DEG below the reset setpoint.
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