YORK YK — Evaporator - Transducer or leaving liquid probe

The control center shows Evaporator - Transducer or leaving liquid probe. On panels that print it in capitals, the same message appears as EVAPORATOR - TRANSDUCER OR LEAVING LIQUID PROBE. The manual lists it among the safety fault messages, and the control's change note calls it a safety fault.

A possibly defective evaporator pressure transducer or LCHLT thermistor has been detected: the pressure and temperature readings from these two devices do not correspond correctly to each other. The LCHLT thermistor is the leaving liquid probe named in the message, and it provides the chilled liquid temperature reading. The control center converts the evaporator pressure into an evaporator saturated temperature value and compares it with the LCHLT; the difference equals chilled liquid temp minus evaporator saturated temperature. If the transducer and thermistor are accurate, the evaporator saturated temperature must not be more than 2.5°F warmer nor more than 25.0°F colder than the LCHLT — in other words, the difference must stay inside -2.5°F to +25.0°F. When the difference leaves that range and stays outside it continuously for 10 min, the control center initiates a shutdown and shows this message.

• A possibly defective evaporator pressure transducer.
• A possibly defective LCHLT thermistor — the leaving liquid probe named in the message.

1. Read the evaporator pressure and the LCHLT reading at the control center, along with the evaporator saturated temperature the control center converts from that pressure.
2. Compare the two values: the difference (chilled liquid temp minus evaporator saturated temperature) should sit between -2.5°F and +25.0°F. Up to 2.5°F warmer or up to 25.0°F colder is the acceptable limit; anything beyond that for 10 min trips the fault.
3. Check the head pressure. This fault is bypassed when the head pressure is less than 5 psid, and the control's change note sets it only when the head pressure is 5 PSID or greater.
4. If the difference is out of range, treat the evaporator pressure transducer and the LCHLT thermistor as the devices to question — they are the two the manual names as possibly defective.

• Acceptable difference: -2.5°F to +25.0°F (chilled liquid temp minus evaporator saturated temperature).
• Trip limits: evaporator saturated temperature more than 2.5°F warmer, or more than 25.0°F colder, than the LCHLT.
• Trip time: difference outside the acceptable range continuously for 10 min.
• Head pressure gate: fault bypassed when head pressure is less than 5 psid; the control's change note sets it only when head pressure is 5 PSID or greater.

Clearing this shutdown is done at the panel: You can start the chiller after the Clear Fault key is pressed on the display. No other reset procedure is described for this message.