Eppendorf North America
Product Manager
Low-temperature freezers are a necessity in any biomedical laboratory, and if you want them to run right, you’ll need to maintain them properly. Nobody enjoys maintenance, but it beats losing all your samples and replacing your hardware. Like anything else, the easier it is to maintain a low-temperature freezer, the more likely users are to do it.
Remove moisture and ice
Buildup of moisture on the outer door of the freezer leads to ice buildup, which in turn can prevent secure outer-door closure. So we recommend wiping down the freezer’s outer-door gasket to remove moisture and prevent ice buildup. If ice is already present, you will need to use an ice scraper instead. But be careful: If you have the wrong ice scraper or scrape too hard, you can actually ruin the outer-door gasket, preventing a good seal.
One of the most vulnerable places on the freezer is the outer-door gasket. The best way to maintain your freezer and prevent ice buildup is to make sure you have high-quality gaskets backed by a comprehensive warranty. If those seals are at all damaged or of poor quality, you’ll have cold air leaving the chamber continuously, and your compressors will need to work overtime to maintain temperature. As the integrity of your outer door decreases over time, you will lose more and more cold air in a kind of domino effect.
Gaskets are available in two basic designs, flat and rippled, and both can be replaced if damaged. At Eppendorf, we use a flat, frost-resistant gasket. This is different from rippled gaskets, which have nooks where moisture can accumulate—moisture that eventually turns into ice.
It is important to remove moisture from the freezer door regularly. Frequency depends on how often the freezer is used, but the more the door is open, the more ice can build up. In general, however, older freezers require more frequent maintenance.
Remember to perform routine filter maintenance, as well. Keeping a clean filter will optimize performance of the freezer. Most freezers notify you when the filter needs to be cleaned.
Defrost the freezer
If ice accumulates to about three-eighths of an inch on the inner and outer compartments of the freezer, you’ll need to defrost it; we also recommend defrosting the entire freezer at least once a year.
Defrosting is a multistep, manual process that takes about two days to complete. First, remove all samples from the freezer and transfer them to another freezer. The transferring of samples should be done in small batches, because if the door is kept open for too long, you will warm up the freezer prematurely. After all the samples have been removed, turn the freezer off, unplug it, open the door and let the ice melt. Make sure to place towels on the floor to soak up the water, or routinely wipe up the melted ice.
Take the opportunity during your annual defrost cycle to evaluate what samples you’re storing. It is okay to get rid of samples that are not labeled, have expired or belonged to researchers who left years ago. This will open room for other, more important samples and make them easier to find.
It generally takes a few hours for a freezer to completely warm up and for the ice to melt. Wipe all moisture from the inside and outside of the freezer. After the freezer is clean, plug it back in and let it come back down to temperature. Eppendorf freezers do not take more than six hours to come down to the desired ultra-low temperature, depending on capacity. But the cool-down process can take up to 12 hours, depending on the freezer’s age and make. Once the freezer has cooled down, transfer samples in batches back into the original freezer.
Additional tips
There are other things you can do to prevent ice buildup. Many freezers are configured with compartments, for instance. Multiple users typically share a freezer, and compartments help segment researchers’ samples to make them easier to find, decreasing time in and out of the freezer and minimizing cold air loss. Some manufacturers add gaskets on their inner doors to prevent even more cold air from being lost during door opening; this also aids in the freezer’s overall performance.
Another suggestion: Use a racking system in your freezer, if available. Drawer-style racks are best, as the user can pull out single drawers instead of the entire rack, thereby reducing loss of cold air and preventing ice buildup.
Nobody said freezer maintenance was fun. But given that your freezers hold the bulk of your research output, it’s a good idea to make sure they’re performing at peak efficiency. Following the tips outlined above will get you well on your way to that goal.
Related Products from: Eppendorf North America