RAUC / RAUJ optional low ambient damper troubleshooting
Description
The damper control (2U83) operates independently of the other controls in the unit. This control is designed to prevent the condenser coil from becoming too cool (RAUC default setpoint 105F and 80F for RAUJ - MCHE)) when the unit is providing mechanical cooling in low ambient conditions. 20-30 ton units use one damper, 40-120 ton units use two dampers. One control (2U83) is provided per unit. The damper is fully modulating 0 to 100%, and is always mounted on the #1 condenser fan outlet for each circuit. The damper actuator (2U84, 2U85) is 0-10VDC direct acting.
Sequence of operation
When the condenser temperature sensor (2RT17, 2RT18) is warmer than the setpoint (5R13, 5R14), the damper will open. When the condenser temperature sensor (2RT17, 2RT18) is cooler than the setpoint (5R13, 5R14), the damper will close. The control responds to condenser temperature only.
Troubleshooting
To force the damper open, short across the sensor input (2TB34-6 and 2TB34-7 circuit 1, 2TB34-11 and 2TB34-12 circuit 2).
To force the damper closed, remove the sensor input (2TB34-6 and 2TB34-7 circuit 1, 2TB34-11 and 2TB34-12 circuit 2).
To test the sensor, measure the DC voltage at the sensor input (2TB34-6 and 2TB34-7 circuit 1, 2TB34-11 and 2TB34-12 circuit 2). Or, remove the sensor and measure the sensor resistance. Refer to this chart for approximate values:
Temp Ohms VDC
40F 26.10K 3.6 VDC
50F 19.85K 3.3 VDC
60F 15.25K 3.0 VDC
70F 11.83K 2.7 VDC
80F 9.25K 2.4 VDC
90F 7.29K 2.1 VDC
95F 6.50K 2.0 VDC
100F 5.80K 1.8 VDC
105F 5.19K 1.7 VDC
110F 4.64K 1.6 VDC
115F 4.17K 1.5 VDC
Setpoint
The default setpoint is 105F (80F RAUJ - MCHE). The setpoint can be changed by replacing the setpoint resistor with one of the values shown:
Wiring Diagram
WARNING:
Information in this article is intended for use by individuals possessing adequate backgrounds of electrical and mechanical experience and who comply with all federal, state, and local laws, rules, orders, or regulations related to the installation, service, or repair of a heating or central air conditioning product. Any attempt to install, service, or repair a heating or central air conditioning product may result in personal injury and/or property damage. The manufacturer or seller cannot be responsible for the interpretation of the information contained herein, nor can it assume any liability in connection with its use.