Most laboratories handle some type of temperature-controlled substance, such as cells, enzymes, and reagents. As such, they often need specialized cold storage instead of basic kitchen models to ensure safe and consistent cooling conditions. This guide will serve as an introduction to buying freezers and refrigerators with extra tips specific to pre-owned equipment.
1. Temperature range and control
There are four categories of laboratory freezers: standard freezer (-20°C), plasma freezer (-40°C), ultralow freezer (-80°C), and cryofreezer (-150°C or lower). Refrigerators are less striated with a general range of 1-12°C. Most freezers and fridges are adjustable to some extent, but occasional models are hard-set to one specific temperature. If you need a greater range of temperatures rather than the factory preset, be sure to check for a control panel or other adjustment interface as well as a manual or other documentation with the unit’s specifications.
2. Defrost type
There are two defrost types for freezers: automatic (“frost free”) and manual. Automatic defrost means the freezer will cycle through cooling and warming periods to prevent frost build up inside the cabinet. Manual defrost means the freezer won’t run through those cycles, and the frost will need to be shaved off by hand.
Most laboratory-grade freezers are manual defrost because they are expected to handle samples that can’t withstand temperature variation. Alternatively, most basic and combination units are automatic defrost for easy maintenance. A simple way to determine a unit’s defrost type is to look at the shelving. Most upright manual defrost freezers will have coils under the shelves to maintain the set temperature; however, ultra low freezers and cryofreezers will always be manual defrost even without visible coils.
3. Display and alarms
Digital displays and alarm systems are becoming increasingly standard with each incoming model. Electronic displays and temperature monitors provide clear and accurate reads of what is happening in the cabinet. Alarm systems help prevent critical errors by alerting scientists of mechanical failures, and they are often supported by liquid nitrogen or carbon dioxide backup systems. If you only need something basic for general storage, you will probably be fine without these bells and whistles. If you need to store fragile samples or you work in an area with frequent power outages, then those bells and whistles could save your research.
4. Flammable material storage vs. Explosion-proof storage
If your lab is handling combustible materials, such as alcohols, you will need appropriate storage to prevent fires and explosions; however, those needs will ultimately depend on your lab environment.
Flammable material storage (FMS) freezers and refrigerators have all electrical components, such as switches and thermostats, on the exterior of the unit to prevent igniting vapors within the cabinet. Additional features may include self-closing doors to prevent combustible vapors from escaping and fortified insulation to limit damage in the case of a fire.
Explosion-proof storage expands upon FMS by requiring complete protection from external vapors. This means all electrical components are outside of the cabinet and completely sealed from the environment. Also, these units will have a heavy duty conduit outlet box to ensure a safe connection directly to the circuit breaker.
Generally, both FMS and explosion-proof storage will have bright labels plastered visibly on the front door warning against holding heat sources near the flammable contents. If the unit does not have any warning labels (which may be possible when buying pre-owned equipment), you can usually determine if it’s fire-safe by looking for electrical connections within the chamber. Regardless, definitely ask your supplier for fire-proof approval or documentation about the unit’s adherence to UL, NFPA, or OSHA standards.
5. Electrical requirements
Most basic refrigerators and freezers will be 115/120 V, 50-60 Hz, and 15 amperes. Lower temperature units will potentially require a greater amperage to operate, such as 20 amperes or more. Many facilities are not equipped for the higher current and, therefore, cannot support heavy duty cold storage. Check your laboratory’s circuit breakers and outlets before purchasing a heavy duty freezer to make sure it can accommodate the greater electrical requirements.
What else do you look for in cold storage? Tell us in the comments below!
Want to see more blog posts, equipment updates, and auction news from BioSurplus? Register for our mailing list here!