AAC/IK/A Chiller - Short Cycling, Error 7 and Continuous Pump Operation
Applies to: AAC/IK/A Series chillers, including AAC/IK/A 110, fitted with an Eliwell controller.
Symptoms
- Compressor ramps up and down too quickly or short cycles.
- The unit generates ERROR 7 due to low-pressure operation associated with rapid cycling.
- The chilled water pump stops when the compressor cycles off, but the application requires the pump to run continuously while the unit is in cooling mode.
- The compressor cut-in / cut-out temperature differential is too narrow.
Likely Causes
| Issue | Likely Cause |
|---|---|
| Compressor short cycling | Insufficient water volume in the primary hydraulic circuit, resulting in low system inertia. A secondary cause may be an unsuitable compressor hysteresis setting at parameter tr30. |
| Pump stopping with compressor | Continuous pump operation parameter P100 is not enabled. |
Service access: Service password is 78. Only adjust the parameters identified in this article. Do not change other controller parameters without authorisation from senior technical support.
1. Compressor Short Cycling
A. Verify System Water Volume - Primary Action
Before changing any controller parameters, confirm that the primary hydraulic circuit contains sufficient water volume.
AAC/IK/A 110 minimum water content: 330 litres
- Confirm the actual water volume in the primary circuit.
- If system volume is below 330 litres on an AAC/IK/A 110, rectify the hydraulic volume before attempting to tune controller parameters.
- Insufficient water volume can allow the leaving-water temperature to change too quickly, causing the compressor to cycle excessively.
B. Adjust Compressor Hysteresis - Secondary Action
If the water volume has been confirmed as adequate, the compressor hysteresis parameter may be reviewed.
| Parameter | Purpose | Reference |
|---|---|---|
| tr30 | Compressor hysteresis | Default: 0.8°C Minimum: 0.5°C |
- Access the Eliwell service menu using password 78.
- Navigate to parameter tr30.
- Review the current value.
- The supplied procedure states that the default value is 0.8°C and may be reduced to a minimum of 0.5°C.
- After adjustment, monitor compressor run and off-times and confirm the system operates without rapid cycling or low-pressure alarms.
Important: The source procedure notes that lowering tr30 increases the temperature differential. Always consider the compressor minimum off-time when changing this parameter.
2. Enable Continuous Water Pump Operation
Where the site requires the chilled water pump to remain running whenever the chiller is in cooling mode, including while the compressor is off, adjust parameter P100.
| Parameter | Required Setting | Result |
|---|---|---|
| P100 | 1 | Water pump operates continuously while the unit is in cooling mode. |
- Access the service menu using password 78.
- Navigate to parameter P100.
- Change the value to 1.
- Exit the service menu and confirm that the water pump remains operational when the compressor cycles off during cooling operation.
Recommended Diagnostic Order
| Step | Check |
|---|---|
| 1 | Confirm hydraulic water volume and correct any deficiency. |
| 2 | Monitor compressor cycling and confirm whether ERROR 7 / low-pressure operation persists. |
| 3 | If required, review parameter tr30. |
| 4 | If continuous pump operation is required, set P100 = 1. |
| 5 | Run the system and verify stable compressor operation, adequate water flow and normal pressure conditions. |
Key point: Controller changes should not be used to compensate for inadequate system water volume. Hydraulic system volume should be verified and corrected first.