Chiller Maintenance

In our daily routines we interact with and use devices that make our lives easier. Items in this category include a furnace for winter warmth, a clothes dryer and automobiles. To keep these devices running properly and safely regular maintenance becomes second nature; such as changing the furnace filter, cleaning the dryer lint filter after each load and periodic maintenance of an automobile’s engine and brakes. This upkeep is paramount to maintain peak performance, safe operation and ensure longevity.

Unfortunately this ‘home’ credo does not always transition into the laboratory. Ubiquitous lab equipment can easily morph into a research ‘white noise’ and become over-looked, taken for granted and forgotten about. Rotary evaporators, vacuum pumps and circulators are frequently used laboratory items that drop off the maintenance radar. Regular inspection and maintenance of these items should be employed to ensure proper operation and a long life time. When was the last time your rotary evaporator vapor duct seal was changed? When was the vacuum pump cleaned or drained? What about the circulator?

 Circulator Maintenance

 Bath Fluid

This component of a circulator is overlooked far too often.  Some questions to review:

  • Do you know what fluid is in the chiller?
  • Is the fluid temperature range denoted?
  • Can the circulator go beyond the temperature range of the fluid?  If so, are there safety features on the circulator that can restrict the temperature setting within the fluid operating range?  Review the operating manual of the instrument and implement safety temperature settings if available.
  • How old is the fluid?  If you do not know the age, change the fluid!  With extended use a general rule of thumb is to change the fluid annually.
  • Does the chiller contain a water immiscible fluid and is it frequently operated below room temperature?  Has the fluid been checked for atmospheric moisture condensation?  Room humidity condenses in hydrocarbon and silicone-based fluids when chilled below ambient temperatures. Over time large quantities of ice can form in the bath fluid which will degrade cooling capacity and possibly affect fluid flow. Inspect and remove as much water as possible from the system before operating again. As moisture accumulates in water / glycol mixtures the low temperature limit will rise.
  • Is the fluid opaque?  This is not a good indicator as contamination from foreign material, water or fluid degradation (cracking) has occurred. The fluid circuit should be drained, flushed adequately and filled with new fluid. The accompanying photo illustrates how a circulator can continue to function despite less than stellar laboratory conditions.
  • Are you using water?  Is the water growing?  Consider adding an algaecide or switching to another fluid that does not facilitate algae growth such as a glycol / water mixture or silicon fluid.


Air-cooled units

When was the last time the condenser vent was inspected and/or cleaned? Most facilities are dustier than you think (clean rooms the exception). The cooling vent should be inspected every 3 months or so and vacuumed to remove debris.


Water-cooled units

Does your water-cooling circuit have an in-line filter before the circulator? If not consider installing one. Facility water contains more particulate matter than you think. If the circulator utilizes a plate heat exchanger the small-bore water channels within can become plugged thereby decreasing the efficiency of the entire circulator.



Place a fluid log on the side of the chiller to denote maintenance dates / fluid changes, etc.  Clearly mark on the unit what fluid it contains and the safe operating temperature limits of that fluid.

Following these maintenance steps and procedures can add years of operating time to a chiller, keep it performing at maximum capacity and ensure safe operation.