Table 9 — Cooling Service Analysis
PROBLEM | CAUSE | REMEDY |
Compressor and Fan Will Not Start | Power failure. | Call power company. |
| Fuse blown or circuit breaker tripped. Check CB1 and | Replace fuse or reset circuit breaker. |
| CB2. |
|
| Disconnect off. | Power disconnect. |
| Compressor time guard to prevent short cycling. | Check time guards using ComfortLinkt Scrolling |
|
| Marquee also the DSC has a 2 minute |
| Occupancy schedule set point or supply set point not | Check cooling demand using ComfortLink Scrolling |
| calling for Cooling. | Marquee. |
| Outdoor temperature too low. | Check Compressor Lockout Temperature using |
|
| ComfortLink Scrolling Marquee. |
| Active alarm. | Check active alarms using ComfortLink Scrolling |
|
| Marquee and DSC alert flash codes |
Compressor Cycles (other than | Insufficient line voltage. | Determine cause and correct. |
normally satisfying demand). |
|
|
Active alarm. | Check active alarms using ComfortLink Scrolling | |
|
| Marquee and DSC alert flash codes |
Compressor Operates | Unit undersized for load. | Decrease load or increase size of unit. |
Continuously. |
|
|
Occupancy schedule set point or supply set point too | Check and adjust set points if needed. | |
| low. Compressor running at lowest capacity |
|
| Compressor contactor stuck on | Check cooling demand using ComfortLink Scrolling |
|
| Marquee and DSC alert flash codes. |
| Dirty air filters. | Replace filters. |
| Low refrigerant charge. | Check pressure, locate leak, repair, evacuate, and |
|
| recharge. |
| Condenser coil dirty or restricted. | Clean coil or remove restriction. |
Excessive Condenser Pressures. | Loose condenser thermistors. | Tighten thermistors. |
| Dirty condenser coil. | Clean coil. |
| Refrigerant overcharge. | Recover excess refrigerant. |
| Faulty TXV. | 1.Check TXV bulb mounting and secure tightly to suction |
|
| line and insulate. |
|
| 2.Replace TXV (and filter drier) if stuck open or closed. |
| Condenser air restricted or air short cycling. | Determine cause and correct. |
| Restriction in liquid tube. | Remove restriction. |
Condenser Fans Not Operating. | No Power to contactors. | Fuse blown or plug at motor loose. |
Excessive Suction Pressure. | High heat load. | Check for sources and eliminate |
| Faulty TXV. | 1.Check TXV bulb mounting and secure tightly to suction |
|
| line and insulate. |
|
| 2.Replace TXV (and filter drier) if stuck open or closed. |
| Refrigerant overcharged. | Recover excess refrigerant. |
Suction Pressure Too Low. | Dirty air filters. | Replace air filters. |
| Low refrigerant charge. | Check pressure, locate leak, repair, evacuate, and |
|
| recharge. |
| Faulty TXV. | 1.Check TXV bulb mounting and secure tightly to suction |
|
| line and insulate. |
|
| 2.Replace TXV (and filter drier) if stuck open or closed. |
| Insufficient evaporator airflow. | Check belt tension. Check for other restrictions. |
| Indoor Fan Running to slow or off while compressor is | Check VFD display is illuminated and shows Auto |
| on | mode. Power supplied to VFD. Check |
|
| present at AUX1 board. |
| Temperature too low in conditioned area (low | Reset thermostat or occupancy schedule. |
|
| |
LEGEND |
|
|
CB - Circuit Breaker |
|
|
DSC - Digital Scroll Controller |
|
|
TXV - Thermostatic Expansion Valve |
|
|
VFD - Variable Frequency Drive |
|
|
48/50PD
Digital Scroll Controller (DSC) Troubleshooting
The 48/50PD units are equipped with a digital scroll compressor. The compressor has a solenoid unloader that is controlled by the digital scroll controller (DSC). This DSC turns the unloader on and off within a 20 second window. The amount of time the unloader is on verses off within that 20 seconds depends on the desired capacity. This means that the ComfortLink control does not have direct control of the compressor, but it does however control the power to the DSC and the signal for commanded capacity.
The DSC has three LED lights to help during troubleshooting; green, yellow, and red The DSC will run the compressor unloaded for a half a second on start up and one second on shutdown to prevent reverse rotation. A two minute
codes and correct any problems. Table 10 shows the DSC’s Red LED flash codes.
POWER LED (green) ⎯ indicates voltage is present at the 24VAC power terminal. When the 2 minute
UNLOADED LED (yellow) ⎯ indicates the unloader solenoid status. The LED is on when the unloader solenoid is energized.
ALERT LED (red) ⎯ communicates an abnormal system condition through a unique flash code.
All LEDs Flashing at the Same Rate ⎯ indicates 24VAC supply is too low for operation.
All LEDs On Solid at the Same Time ⎯ indicates Digital Scroll Controller failure.
Flash Code 1 ⎯ Reserved for future use
Flash Code 2 ⎯ High Discharge Temperature
This occurs when the discharge temperature thermistor (DTT) has
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