The unintended consequences of a poorly maintained ultra-low temperature freezer can include catastrophic loss of potentially irreplaceable samples and losing compressor efficiency over time. According to a US Department of Energy report, an Ultra-low temp freezer can use similar amounts of energy as an average household over the course of a year. These are just a couple of reasons proper ultra-low temp freezer maintenance and troubleshooting is considered a high priority.
We recently conducted a webinar for individuals in Biomed and Facilities departments to share information on troubleshooting and maintenance tips on ultra-low temp equipment. We want to share several questions that were addressed by Mark Kehoe, Helmer Scientific Technical Services Representative, and Brian Hoaglan, Helmer Scientific Low Temp R&D Manager during this live event:
How frequently should I defrost my Ultra-low temp freezer?
There is no industry-standard rule around frequency of defrosting ultra-low temp freezers. However, defrosting at least annually is common. The appropriate defrost frequency for your freezer will likely depend on the condition of the ultra-low temp freezer, the amount of usage/door openings, and the environment in which it is being operated. Defrosting should be expected as all ultra-low temp freezers will draw moisture and warm humid air into system. The location of the frost build-up can be a good indicator that it is time for a manual defrosts. If frost is just visible on the outside of internal doors, or outside of compartments used for sample storage, defrosting is likely not required as often. If frost builds up within cabinet near samples, the frost may affect the amount of heat absorbed by the system and begin to affect performance (and should be defrosted more often).
There are two situations that should trigger a defrost in the near-term. First, any frost build-up that interferes with door openings. This frost could create stress on door gaskets, and/or prevent proper seal. Second, frost build-up that makes it difficult to access racks and accessories during normal operation should be addressed quickly. This type of frost build-up can make it difficult to retrieve samples, and can inadvertently lead to longer routine door openings.
What clearance requirements are needed for proper performance for an ultra-low temp freezer?
Clearance requirements definitely vary by manufacturer, but typically around 8 inches are required behind the unit. Depending on the locations of the exhaust vents, your unit may also require up to 8 inches on sides based on manufacturer’s recommendations. The front of ultra-low temp freezers should be clear and open as that is where most units have air intake for compressors. Many manufactures utilize stand-off brackets to help guide appropriate installation. Ensure these stand-off brackets are available and installed according to the manufacturer of your freezer to ensure proper performance, and long freezer life.
What is the control range of the freezer?
Most ultra-low temperature freezers have control ranges designed for -50°C to -86°C, but you need to refer back to your manufacture for information on your specific model. Most applications for this category of equipment will be between -70°C and -80°C. If -70°C is appropriate for your samples, it is recommended to set the ultra-low temp freezer at -70°C instead of -80°C, or -86°C. This modest increase in temperature allows the ultra-low temp freezer to operate using less energy while still protecting many sample types. Users should be cautioned against setting temperatures higher than the range recommended by their manufacture. These higher temperatures could be hard on unit, as an ultra-low temperature freezer is not designed to take the place of freezers that run at -30°C or -40°C. Avoid damage to your ultra-low temperature freezer by staying within the recommended control range.
For more information on ultra-low freezer troubleshooting and maintenance tips, download the complete webinar.