York YPAL 051 Outdoor Humidity Sensor Alarm, Return Humidity Sensor Alarm, IAQ CO2 Sensor Alarm

Service

Outdoor Humidity Sensor Alarm (29)

This alarm indicates the outdoor humidity sensor is out of range. When this occurs the Unit Controller will switch economizer operation to Dry Bulb. The Outdoor Humidity analog input is at OH+ wire 333 of the P6 connector and OH- wire 334 of the P6 connector. To trouble shoot the sensor verify 24 VAC between terminals EXC and COM of the sensor. Also verify the VDC between the OUT and COM connection of the sensor. If no voltage is present replace the sensor.

Return Humidity Sensor Alarm (30)

This alarm indicates the return humidity sensor is out of range. When this occurs the Unit Controller will switch economizer operation to Single Enthalpy. The Return Humidity analog input is at RH+ wire 335 of the P6 connector and OH- wire 336 of the P6 connector. To trouble shoot the sensor verify 24 VAC between terminals EXC and COM of the sensor. Also verify the VDC between the OUT and COM connection of the sensor. If no voltage is present replace the sensor.

IAQ (CO2) Sensor Alarm (31)

This alarm indicates the IAQ (CO2) sensor is out of range. When this occurs the Unit Controller will switch the ventilation mode from Demand to Fixed Minimum. The IAQ sensor input is at terminal DV+ and DV-. This device is field supplied.

Time Clock Error Alarm (32)

This alarm indicates the Unit Controller Real Time Clock is not functioning. The Unit Controller will shut down all operation. Try recycling power to the control. If the fault reappears replace the Unit Controller.

Space Temperature Offset Alarm (33)

This alarm is generated when the resistance in the Space Temperature Offset circuit is greater then 20,000 ohms. The Space Temperature Offset input is at terminals SSD and GND of the P6 connector. Check the resistance between these to points. If greater then 20,000 ohms check the tightness of the connections and the wire wiring between the Unit Controller and the space sensor. If both are okay and the resistance is still greater then 20,000 ohms replace the space sensor reset.

FORM 100.50-NOM6 (1207)

CV/VAV Input Alarm (34)

This alarm indicates the resistance between terminals CV/VAV and CV/VAV at the P7 connection is out of range. The acceptable range is 0.0 to 20,000 ohms. Check the resistance between the two CV/VAV terminals and take appropriate action.

Low Voltage Alarm (35)

The Unit Controller monitors the 24 VAC input to the control. The input has two thresholds. The voltage must be above 19.2 VAC or the control will not turn on a contactor. If the voltage is not above this value it will not turn on the contactor and flashes the fault code. If contactors are energized and the voltage drops below

16.0 volts the Unit Controller will de-energize the contactors and flash the alarm. To trouble shoot check the voltage between the “R” and “COM” at the ¼ inch terminals on the board.

Smoke Purge Mode Alarm (36)

This is not an alarm but rather an indication the unit has been placed in a smoke purge mode. Verify the presence of 24 VAC between PURGE connection at the P3 connector and “C” on the P1 connector. If 24 VAC is present and the unit is not supposed to be in the Purge mode trace the field wiring to determine why the voltage is present.

High Duct Static Pressure Alarm (37)

This alarm indicates the duct static pressure has exceeded the Duct Static Shutdown Setpoint. The problem could be caused by a faulty Duct Static Pressure Transducer input. To check measure the VDC input between terminal DP+ wire 337 at the P21 connector and terminal DP- wire 338 at the P21 connector. Compare the voltage verses the duct pressure the control indicates to Table 8-2 in this section of the manual. Also verify that 24 VAC is present between terminals “COM” and “EXC” at the duct static transducer.

166 JOHNSON CONTROLS