When a chiller fluctuates quickly around the set point, this is typically a low fluid flow issue. Many times this is due to contamination in the chiller, specifically inside the quick disconnect fittings on the chiller.
More than likely, there is particulate contamination collecting at the supply-side quick disconnect fitting on the chiller. The supply-side fitting is the top fitting on T257P chiller and the bottom fitting on a Rack-Mounted chiller. This restriction is causing low fluid flow through the fittings and chiller, causing the instability.
Empty your chiller of fluid and remove and clean (or replace) both fluid fittings on the chiller, then reassemble and retest. Cleaning or replacing the fluid fittings is an important step. The connectors on the side of the unit that your system plugs into are removable. If you use a wrench or pliers, they will unscrew from a fitting inside the chiller. Remove them over a sink or bucket, as the fluid will pour out. Clean the inside of that connector and pour a liter or so of distilled water into the reservoir to flush any additional material out. When you reinstall the fittings, ensure the threads are dry then use clear silicone sealant on the threads to prevent leaks. The flow should return to normal and the temperature should stabilize.
Please confirm that your chiller reservoir is full, the pump is working and fluid is flowing back through the chiller when in Cooling mode. If the pump is not working or if you cannot tell if the pump is working, refer to Question 3 below.
If you have confirmed that fluid is flowing through the chiller, check the Control Mode of the chiller (T257P only) to ensure the setting is the default HIFLOW setting. The Control Mode can be found by cycling through the main menu when the chiller is powered on and in Standby mode.
Monitor Screen:
Many times when a chiller is no longer pumping fluid this can be due to air lodged in the pump, preventing fluid from pumping correctly. To test your chiller function and remove any air from your pump, run the following setup and test.
Check the Control Mode of the chiller (T257P only) to ensure the setting is the default HIFLOW setting. If the Control Mode is set to LOFLOW (Low Flow), change it back to the default HIFLOW. The Control Mode can be found by cycling through the main menu when the chiller is powered on and in Standby mode.
Cooling Fluid options:
NOT Acceptable Cooling Fluid:
The low coolant level alarm is typically triggered by the float switch inside the reservoir. If the chiller has been emptied of fluid for a period of time, microdeposits can form between the clear plastic float and the base of the shaft causing the float to be lightly adhered to the bottom of the shaft. If this is the case, you can gently tap the plastic float which will break it free from the microdeposits that were holding it in place. This should allow your chiller to begin working normally again.
If the float is already freely floating on the shaft then likely the entire float assembly, or control board that it plugs into may need replacing. Contact ThermoTek if you would like to arrange for an RMA to return your chiller for a repair quotation.