Research freezers and refrigerators are critical to supporting research at UVM. Any loss of temperature control can damage research materials, sometimes delaying or even ending a research project and jeopardizing your research funding.

Proper use and preventive maintenance is important to keep your unit functioning properly and to protect your research materials.

Preventive Maintenance: Freezers

The operator should perform routine cleaning and maintenance. For maximum performance and efficiency, it is recommended that the unit be checked and calibrated periodically by a qualified service technician.

The following is a condensed list of suggested preventive maintenance requirements. Refer to the owner’s manual for specific details for each piece of equipment. Cleaning and calibration adjustment intervals are dependent on use, environmental conditions, and accuracy required.

  • Fill an upright by starting at the bottom near the probe and add racks to one shelf at a time. Allow freezer to recover to set point between shelves.
  • Fill chest freezer by starting at the left side near the probe. Filling with room temperature racks will result in long pull-down time.
  • Fill the unit with frozen product to help overall performance, frozen water jugs, for example.
  • Always make certain the vacuum relief port is free of frost and ice, to allow for timely re-entry into the freezer after a door opening.
  • Unit needs space to breathe, 6” is a good general rule, could be less per the owner’s manual.
  • Unit must be connected to properly sized and dedicated breaker.
  • Inspect all probe ports, make sure they are sealed during and after use. Do not drill/screw the case in any way without consulting the manufacturer.
Maintence Chart
Action Monthly 6 mos Yearly
Verify that ambient temperature is < 90°F.    
Check and clean probe cover gaskets, hinges, and lid(s) of ice and snow.
More frequent cleaning may be required, depending on use and environmental conditions.
Check air filter. Clean or replace as needed.     ✓ 4X
Vacuum condenser coils as needed. (Use caution - SHARP)    
Clean unit with mild detergent, use baking soda and water to treat odors.    
Verify the unit alarms are active and limits are properly set for the content.    
Check alarm back-up battery, replace* as necessary.    
Check chart recorder backup battery (9V), replace* as necessary.    
Inspect gaskets for tears and replace if compromised. Clean with mild detergent, check seal with dollar/paper test**.    
Vacuum condenser condensate pan. Use CAUTION as most pans have a heater for evaporation - may be HOT.    
Defrost freezer at 3/8" frost thickness. (Must be turned off for 24 hours before restarting)    
(as required)
Adjust door handle for firm latching, as needed.    
Clean condenser compartment and wipe off condenser.    
Verify and document calibration, at a minimum annually.    

*Dispose of batteries properly through Risk Management & Safety

**Dollar/paper test: Close freezer door on dollar bill or piece of paper. If door seals properly, you should have difficulty removing the dollar or paper. If it is easy to remove paper, the gasket may need to be replaced.

To minimize ice build-up inside of freezer:

  • Locate the freezer away from drafts and heating/cooling units.
  • Keep the number of door openings to a minimum.
  • Minimize the length of time door is open.
  • Make sure the door latches securely after opening.

Defrosting your Ultra Low Temperature (ULT) Freezer

Read your owner’s manual and follow the steps recommended by the freezer manufacturer.

The recommendations below are only basic guidelines.

  • Remove all contents and transfer to alternate ULT.
  • Following the manufacturer's instructions, turn the unit off and disconnect from power.
  • Turn off the battery switch (back-up battery).
  • Check owner's manual to determine whether the unit has a drain.


Whenever possible, move ULTs to a location with a floor drain. This provides a safe path for the water to drain. If ice is allowed to melt in a lab without a floor drain (or other precautions), areas located below the lab may receive water damage

Check defrosting ULTs periodically, at a minimum every 2 hours while ice is present


For chest freezers, open the lid and remove the sub-lids. If there is ice build-up on the sub-lids, place on towels.

  • If there is no drain, place towels on the chamber floor and along the hinge.
  • If there is a drain, place a pan under the drain and open the drain.

For upright freezers, open the outer and all inner doors.

  • If there is no drain, place towels inside each compartment.
  • If there is a drain, place a pan under the drain and open the drain.

Allow the ice to melt and become loose. Loose ice can be placed in a sink or pan to melt. DO NOT REMOVE ICE USING A SCREW DRIVER, ICE PICK, OR SIMILAR DEVICE.

Do not dispose of ice in biohazard waste. If concerned about biological contamination, decontaminate per biowaste management guidelines.

  • Use secondary bin to catch water as ice thaws in an upright freezer.
  • Safety staff can supply cotton rags to help absorb water in the freezer.

Allow ULT to defrost for 24 hours. This allows both the interior and refrigerant system to warm to room temperature. Continue to check on melting ice, and ensure the water is contained and soaked with towels or other absorbents.

Once ULT is at room temperature, clean with a mild soap solution or a solution of sodium bicarbonate and warm water. Bleach is often not recommended for freezers that will be kept in service. However, if used, follow with a soap and water solution.  Rinse with clean water and dry with a cloth or towel.

  • NOTE: For disposal, use bleach for decontamination of biological materials.

Close the door/lid of the ULT, and restart the freezer. Allow it to come to temperature before reloading with your contents (some manufacturers recommend 24 hours).

Preparing For Unexpected Failures or Outages

If you have valuable and/or irreplaceable materials that rely on the mechanical equipment to maintain appropriate temperature, then you should install a monitor or alarm. There are two types of monitor/alarm systems in use at UVM that alert lab personnel to storage conditions that exceed lab-defined parameters. Either can be used for freezers, refrigerators, LN2 dewars, warm rooms and other equipment and space.

  1. Sensaphone: Sensaphone monitors are installed by UVM Physical Plant. Submit a FAMIS Service Request. This system uses UVM network connection, which labs may need to pay to be installed and/or activated. There is an initial purchase price as well as costs for PPD to install. PPD does not respond to these monitors/alarms.
  2. Minus80: Minus80 monitoring is a system used in several institutions around the country. They provide monitoring and alert services that are customized to each lab's need. These systems report temperature fluctuations over time as well as alerts for temperatures that exceed a given range. Minus80 personnel monitor alerts along with lab personnel. These systems communicate using Minus80 telecommunications equipment. Labs pay an initial purchase cost as well as monthly service charges. Contact Minus80 for more information or to set up this service.

see imageConsider the materials you are storing by following this flowchart