Ultra-low temperature (ULT) freezers are commonplace in laboratories, biorepositories and research hospitals as they are crucial for preserving the shelf life of biological samples such as enzymes, tissues, bacteria and vaccines. These freezers provide more accurate and reliable temperature control than conventional freezers while maintaining an extremely low-temperature range, typically between -50°C and -86°C. ULT freezers are crucial in the life science and clinical research fields, but they can require careful maintenance to keep them operating smoothly.
Finding an Ultra-Low Temperature Freezer
When deciding on a ULT freezer, the criteria that you focus on will depend on the requirements for storing your samples safely. The size of the freezer will be determined by the storage capacity you need and the space available in your facility. Upright ULT Freezers usually allow for the most storage without taking up a large amount of floor space. If you are not planning on storing a large number of samples, or if you are not working with large samples, you can look into smaller freezers to serve your purpose.
Temperature range is also a key factor in choosing a ULT freezer. Your choice should depend on the types of samples you plan to store, as some samples require even lower temperatures than others. Stirling Ultracold ULT freezers offer the widest usable temperature range by supporting stable setpoints between -20°C and -86°C.
Ultra-Low Temperature Freezer Best Practices
Properly managing a ULT freezer is key to maximizing its life and efficiency. By being a step ahead of the challenges that come with a ULT freezer, you can ensure that your ULT freezer is set up and maintained properly for sustained operation and efficiency.
1. Consider Freezer Placement and Infrastructure Needs
One of the most important steps you can take when purchasing a ULT freezer is to ensure that the facility space is well-equipped to handle the large, high-powered freezer.
Suitable Electrical Sources
Maintaining an ultra-low temperature can require significant power. You should be sure that your planned power source provides sufficient and proper voltage for the selected freezer model and will not be overloaded by multiple high-powered devices. Some ULT models, such as Stirling units, can operate at multiple voltages, thereby avoiding facility rewiring and easing conformance to diverse power requirements around the world. Backup power is often a requirement to avoid loss of high-value and sometimes irreplaceable biological assets that are stored in ULT freezers.
Adequate Ventilation and HVAC
ULT freezers can also produce large amounts of heat, meaning that having too many freezers in one space can make cooling more difficult. Most ULT freezer models should operate in an ambient temperature setting that does not exceed 32°C, although Stirling models can be safely operated at ambient temperatures above 35°C.
Enough Floor Space to Open the Freezer Door
Having adequate space for the freezer also allows airflow around the freezer and ventilation, which is crucial for them to function properly. ENERGY STAR®-certified freezers are beneficial as they produce less heat and can reduce HVAC requirements.
Freezer Capacity for storing materials
Ultra-low freezers operate best when the cold air within is uninterrupted and storage space is maximized. Sample materials should be well organized and managed in the freezer to ease retrieval and ensure the shortest amount of time possible that the door remains open. Laboratory supplies and materials should not be stacked on top of the freezer, which can trap warm air causing the freezer efficiency to decrease over time.
Temperature monitoring and data loggers
Many ULTs have a built-in temperature monitoring system, which includes high and low alarms and data loggers. Remote and cloud-based monitoring systems can alert you by phone or email if the cabinet temperature is too high and notify you if temperature recovery is necessary so that you can act quickly. It is also possible to upgrade to more advanced systems which include backup cooling and ambient temperature alarms.
2. Perform Regular Maintenance
As with any lab equipment, performing preventative maintenance goes a long way toward preserving the equipment and ensuring it continues to work efficiently. Maintenance tasks include regularly cleaning and replacing the condenser filter, routinely defrosting the freezer, and calibrating your freezer on a regular basis.
Clean Your Unit Regularly
For compressor-based units, dust often builds up in the condenser. Cleaning the condenser filter will ensure that the freezer can properly cool the samples. To do this, you can hire a service to clean the filter, or you can vacuum around the condenser coils yourself and then remove and rinse the filter.
De-icing and Defrosting your Freezer
Regularly defrosting/de-icing the freezer is also key to your ULT freezer running effectively. Ice build-up in the freezer can damage the inner doors, cause the appliance to overheat and put your valuable samples at risk. You should de-ice the freezer as needed and plan on defrosting the freezer one to two times per year.
Calibrate Your Freezer
Ongoing use can cause the freezers monitoring system and probes to become less accurate. A freezer should be calibrated as often as the standard operating procedure (SOP) indicates, but usually once a year is sufficient.
Frequently Asked Questions
What are ultra-low temperature freezers used for?
Ultra-low temperature freezers are used for preserving biological materials such as bacteria, tissues, vaccines and a variety of biospecimens for research.
How cold are ultra-low temperature freezers?
ULT freezers interior cabinets can reach temperatures as low as -86 °C.
How long do ultra-low temperature freezers last?
ULT freezers usually last about 10 to 12 years if maintained properly.
How do you defrost an ultra-low temperature freezer?
An ultra-low temperature freezer should be defrosted at least once a year by removing all of the samples, turning off the freezer for several hours and letting the ice melt. Most freezers will defrost within six hours, depending on the size.
For more information about ULT freezer best practices, contact us at Stirling Ultracold.