Best practices and helpful tips
Defrosting and maintaining biotech freezers, particularly ultra-low-temperature (ULT) freezers at -80°C and standard lab freezers at -20°C, is crucial for protecting sensitive samples, maximizing freezer lifespan, and ensuring optimal energy efficiency.
Best Practices for Defrosting Biotech Freezers
Frequency
-80°C Freezers: Every 6 months or when ice buildup exceeds 5 mm
-20°C Freezers: Every 3 to 6 months or as needed
Preparation
Notify stakeholders: Ensure all users know the schedule in advance.
Transfer Samples
VFP strongly recommends having a backup freezer for each temperature and capacity. Preferably, empty but at a minimum with enough space to store transferred materials in an organized fashion.
- Evaluate and plan sample transfer. Are samples in freezer racks, loose, both? If backup unit is empty and same capacity can we organize and mirror transfer? Communicate plan to researchers, document sample locations.
- Limit time out of ULT conditions to prevent sample degradation.
- If possible, use this time to work with researchers and label, organize, and possibly dispose of unneeded samples. This will streamline freezer organization, inventory management, and freezer return post-defrost.
Defrosting Steps
- Turn off alarm monitoring.
- Shutdown, turn off power switch, unplug the unit.
- If the unit has an external alarm battery, unplug the wire.
- Remove excess frost into a container, keep an eye out for possibly loose small sample tubes!
- Place absorbent pads or trays on each shelf and at the bottom to collect meltwater.
- Ensure the door remains open during the entire defrost process to allow warm air to enter and accelerate melting.
- Clean the interior with 70% ethanol or mild detergent.
- Wipe down thoroughly and confirm interior is completely before restarting to prevent re-freezing of moisture.
Ongoing Maintenance Best Practices
Ice Management
Open the door only when necessary and briefly.
Weekly Maintenance
- Check door seals for cracks or gaps.
- Wipe down gaskets and door edges with ethanol or mild detergent.
- Log temperature and alarm history (preferably digital or cloud-based monitoring).
Monthly Maintenance
Carefully use a towel to remove visible frost or ice buildup early. Especially focus on the door gaskets and seals.
Quarterly Maintenance
- Inspect vents and filters:
- Clean air intake and exhaust vents.
- Test alarms and backup power systems.
Annual Maintenance
- Fully defrost and clean as outlined above.
- Service by a certified technician. Check compressors, temperature sensors, and refrigerant levels.
Additional Tips for ULT Freezers (-80°C)
- Utilize a sample inventory system (such as a barcode or digital map) to minimize door-open time.
- Avoid overloading or underloading the freezer; air circulation is critical.
- Group samples by shelf to minimize time searching with the door open.
- Thousands of ULT freezers around the world are now set to -70 °C instead of the usual -80 °C. We call this “chilling up” your freezer! This setpoint change can result in a 30% energy savings for your ULT freezer and puts less strain on your unit.
Be sure to get permission from your lab before changing your freezer set-point.
Venture Forward Partners is a full-service Laboratory Planning, Project Management and Lab Services provider for life science and biotech laboratories in Greater Boston. From site selection and lab relocations to setting up and maintaining your lab, we provide a broad range of services and solutions to support your lab operations. Our team possesses unparalleled energy and enthusiasm towards the work we do, and we have the expertise, training, hands-on lab experience and industry connections to ensure your lab’s success. Whatever your lab needs – we make it happen.