YORK YCAV — LOW SUCTION PRESSURE FAULTS CAUSED BY LOW FLOW

The panel shows LOW SUCTION PRESSURE FAULTS CAUSED BY LOW FLOW. The manual prints the message in this wording only, so no alternate display text applies. The same manual group also contains a separate message, LOW SUCTION PRESSURE FAULTS CAUSED BY LOW SUBCOOLING; this page covers only the low flow fault.

The manual's fault table defines this message as a low suction pressure fault caused by evaporator flow near or below the minimum allowed. In other words, low water flow through the evaporator is the suspected reason the suction pressure fault appears: if flow is near the minimum, or below the minimum allowed in the IOM, it may be causing the low suction pressure fault.

• Evaporator water flow near, or below, the minimum flow allowed in the IOM.

1. Check the approximate flow across the evaporator using a flow meter or the pressure drop charts in the IOM.
2. If the flow cannot be measured with a flow meter, or there is doubt about the accuracy of the flow pressure drop measurement, run a single system on the chiller and check the temperature differential across the evaporator (return minus leaving water temperature).
3. Compare the measured differential with the single-compressor threshold values listed in the thresholds section to decide whether low flow should be suspected.

• Two system chiller: low flow should be suspected if only a single compressor is running fully loaded and the temperature differential across the evaporator is greater than 8°F.
• Three compressor system: a temperature differential greater than 5.3°F with a single compressor running is suspect.
• Four compressor system: a temperature differential greater than 4°F with only a single compressor running is suspect.