A laboratory freezer often protects valuable medical or scientific materials that may be the basis of your lab operations. With a function that important, the laboratory freezer you choose needs to be reliable, needs to have accurate temperature control, and needs to be the right type to fit your lab's requirements.
Laboratory freezers come in distinct types broken down by temperature and configuration.
Temperature
There are three common temperature categories of laboratory freezer including general purpose with pre-set temperatures between -20 and -30 degrees C, low-temp with pre-set temperatures between -30 and -45 degrees C, and ultra-low temp with pre-set temperatures between -45 and -86 degrees C. All pre-set temperatures are adjustable, but only within a narrow range, so it's important to match freezers you're considering with your temperature requirements.
Configuration
Lab freezers come in two common configurations; upright and chest. Uprights can be further divided into free-standing and undercounter.
Upright Freezers
Upright freezers have the advantage of being easier to organize. Usually upright freezers have more shelves and you can relocate items in the freezer without having to remove other items that may be on top.
Larger uprights typically also have additional storage in the door which provides extra flexibility to store frequently used materials for quick access when needed.
Undercounter upright freezers are particularly good for storing smaller materials you need frequent access to because they can be placed out-of-the-way near the work station that uses them.
The disadvantage of upright freezers lies in temperature control. When you open an upright freezer, frigid air wants to spill down from the freezer. The drop in temperature can be dramatic making it more difficult to maintain a desired temperature. The more times you must open the door to conduct lab operations, the more pronounced the effect will be.
Something to consider when purchasing an upright lab freezer is inner compartment doors. Particularly for temperature sensitive materials, inner compartment doors allow you to control the temperature more precisely for those items protected by the doors. The temperature in the remainder of the compartment may fluctuate more with the opening and closing of the main door, while materials behind the inner compartment doors remains constant or closer to constant.
Another feature of some freezers is the ability to adjust temperature automatically and quickly each time the door is opened. This can make up for the lack of internal compartments and give you more flexibility in storage organization.
Chest Freezers
Chest freezers are more difficult to organize because you must layer items on top of each other. To access items on the bottom, you must remove something from the top.
One advantage of chest freezers is that they can store larger material containers than an upright. Chest freezers are best at longer term or bulk storage of materials.
Temperature control is much easier with a chest freezer because you open the door from the top and the frigid air tends to stay in the chest instead of spilling out.
Combination Freezer/Refrigerator
If you need both a refrigerator and a freezer, instead of taking up the space for two separate units, you can buy a combination unit that includes a separate freezer and refrigerator. They have separate doors for each function along with separate temperature controls and can be equipped with separate alarms and sensors. They may be just the thing for labs that are tight on space.
There are other considerations when choosing a laboratory freezer.
Size
How big does your freezer need to be? Only you can answer that question, but it's an important one.
How much space do you have to dedicate to the freezer? You may want a large chest freezer, but if you don't have the space, then it won't solve your problem. Keep in mind that uprights also allow you to store more material in a smaller footprint.
Are you storing large containers for extended periods? Then a large chest freezer may be the answer.
Is the organization of the materials very important to reduce lab errors? An upright would be the right choice.
Do you need frequent access to the materials in the freezer? You should probably choose a small or undercounter model that you can place near your workstation.
An analysis of your situation may reveal that you need more than one freezer to satisfy your requirements.
Location. Location. Location.
If you're planning to place your new freezer in a new location, you need to be mindful of the needs of the freezer. First, freezers don't do as well in warmer rooms. It makes their compressors work harder and reduces their useful life.
Also, freezers work better with clearance on all sides to enhance air circulation. Placing them against a wall or close to other equipment can cause overheating and failure.
Finally, freezers create heat all by themselves which raises room temperature making the compressor work harder. Be careful not to place too many freezers in the same area to avoid raising the temperature of the room too much for all the freezers to operate efficiently.
Temperature Control
Many lab materials or specimens must be kept at precise temperatures to insure their viability. With that in mind, if you need that level of control, make sure you choose a model with precise temperature control.
Many newer models have microprocessor controlled thermostats that are much more accurate than older manual, dial-type or analog units and even allow temperature settings accurate to one decimal place.
Alarms
No matter how reliable or high-quality your freezer is, the possibility of unforeseeable, catastrophic failure is always a possibility. With that in mind, if you store valuable materials you can't afford to lose, a built-in alarm system is a necessity. Some systems can provide remote alarms even alerting you via email, text, phone, or pager in addition to giving off an audible alarm when temperatures rise above limits.
Temperature Sensors
Some disciplines, like medical, biological, and food and drug for example, require careful documentation of temperature for validation. Sensors are available that collect data that can be used to validate both material and air temperature as required. Data can be stored for retrieval locally or remotely as needed.
Manual Defrost
Manual defrost units are subject to ice buildup on interior walls which must be removed periodically. That means that materials in the freezer will have to be removed and provided with alternate temporary storage during the process. Time will also have to be allotted while the freezer cools enough to return the materials to the freezer.
Automatic Defrost
Many auto-defrost lab freezers use heat to defrost condenser coils which, when in operation, will cause the temperature inside the freezer to rise. Heat plus air circulation removes any ice on the walls of the unit, but can put materials inside the freezer at risk if this situation is not part of your planning.
Often, just keeping the unit full is enough to prevent a substantial change in temperature, however ice packs can be used to help. Mainly, you just need to be aware of the impact of the auto-defrost cycle on the freezer's contents.
Newer units have the capability to shorten defrost cycles and can be configured to shorten the cycle when temperatures rise above a specified temperature. Shorter automatic defrost cycles reduce the risk to lab materials.
Automatic defrost units use more energy efficient than their manual defrost counterparts.
Security
In your industry, you may require everything from locks on the freezer door to a record of when a freezer door was opened and who opened it. You can find basic lockable doors on many freezer models, but for more elaborate systems you will need to opt for more expensive or even custom models.
Material Visibility
Inventory management or physical security can be as simple as being able to see what's available. In the case of a freezer, it can be as simple as an insulated glass door. Basic upright freezers come with solid doors often with storage shelves or bins in the door. Models with insulated glass doors are more expensive and do not have the extra storage in the door.
Upright Freezer Door Reversibility
It's common now for single-door upright lab freezers to have reversible doors to enhance the flexibility of locating the freezer in your lab. If that's a capability you may need, be sure and confirm that the freezer you're considering has a reversible door.
Material Construction
Freezers come with coated or stainless steel interiors and exteriors. Stainless steel is resistant to stains and rust while painted steel surfaces when scratched can be at risk for corrosion. More than just aesthetics, stainless steel is a more durable material that can make the freezer easier to clean and prolong the life of your freezer.
Safety
Any unprotected electric device can be a safety hazard in the wrong environment. Loose wires, short circuits, and blown lights can all cause sparks which in the presence of an oxygen-rich environment or flammable chemicals can cause a fire or explosion. If this is a concern, units are available that are designed to be explosion-proof.
I sincerely hope that this article has provided you with valuable information that helps you choose the best laboratory freezer for your needs.