Why isn't my chiller reaching its set temperature?
If your recirculating chiller is running but the process fluid is not reaching the required set temperature, it does not necessarily mean that there is a fault with the refrigeration system.
Cooling performance depends on several factors, including the process heat load, ambient conditions, airflow, process fluid, and coolant flow.
Before contacting ATC for support, there are several straightforward checks you can make.
Is the heat load too high?
Every chiller has a defined cooling capacity, and the amount of cooling available varies with operating conditions.
If the process is generating more heat than the chiller can remove, the fluid temperature may remain above the setpoint even though the chiller is operating continuously.
Consider whether anything has changed since the system was originally specified. For example, has the process heat load increased, has additional equipment been connected, or is the process now operating at a different temperature?
If the chiller has never achieved the required temperature in the application, it may also be worth checking that it was originally sized for the actual process heat load.
Is the ambient temperature too high?
Ambient temperature affects the performance of an air-cooled chiller.
As the temperature of the air entering the condenser increases, it becomes more difficult for the refrigeration system to reject heat. The cooling capacity available from the chiller can therefore change with ambient conditions.
Check the temperature immediately around the chiller, rather than relying only on the general room temperature.
Nearby machinery, confined spaces and recirculating hot discharge air can all create a local temperature significantly higher than elsewhere in the room.
Is there enough airflow around the chiller?
Air-cooled chillers need unrestricted airflow through the condenser to reject heat effectively.
Check that:
- Air inlets and outlets are unobstructed
- The required model-specific clearances have been maintained
- The chiller has not been enclosed or positioned too close to another surface
- Hot discharge air is not being drawn back into the chiller
- Accessible air filters are clean, where fitted
- The condenser is not visibly obstructed by dust or debris
Always follow the cleaning and maintenance instructions in the manual for your particular chiller.
Is the correct process fluid being used?
The process fluid affects both heat transfer and hydraulic performance.
Check that the fluid in the system is the type and concentration specified for the chiller and application.
Using a different fluid, or an incorrect water/glycol mixture, can affect the cooling and flow characteristics of the system.
If the fluid has recently been changed, check that the replacement is appropriate for the operating temperature and compatible with the chiller.
Is there sufficient coolant flow?
The chiller needs an appropriate and continuous flow of process fluid to transfer heat effectively.
Check for obvious external causes of restricted flow, including:
- Closed or partially closed valves
- Kinked or damaged hoses
- Blocked external filters
- Restrictions within the customer’s process
- Incorrectly connected pipework
- Air within the cooling circuit
Remember that pumps create flow, while pressure develops as that flow encounters resistance within the customer’s circuit.
If the pipework or process is more restrictive than expected, the actual flow available may differ from the original requirement.
Do not completely close the chiller outlet or bypass in an attempt to alter the flow or pressure.
Is the chiller suitable for the required temperature?
Operating temperature ranges are model and configuration specific.
If you are attempting to operate outside the standard temperature range of the chiller, it may not be capable of achieving requested setpoint in its current configuration.
Some compatible ATC chillers can be supplied with dedicated Low Temperature or High Temperature Option Packs to extend their operating capabilities.
If you are unsure of whether your chiller is suitable for the required temperature, check its specification or contact ATC.
What if the chiller still won't reach temperature?
If the external checks above do not identify the cause, contact ATC.
To help us to investigate, please provide:
- Chiller model
- Serial number
- Required temperature setpoint
- Actual fluid temperature
- Ambient temperature around the chiller
- Process fluid being used
- Known flow rate and system pressure information
- Details of the application and estimated heat load
- Any alarm or error messages
- Information about when the problem started
- Details of any recent changes to the process or installation
A photograph of the chiller rating plate can also help us to identify the equipment and its original specification.
Should I investigate the refrigeration circuit myself?
Do not open, modify, or adjust the refrigeration circuit as part of troubleshooting.
If the chiller is correctly installed, has appropriate airflow and coolant flow, is operating within its specified conditions and still cannot maintain temperature, the equipment may require further technical assessment.
Work on the refrigeration system should only be undertaken by appropriately qualified personnel.
