Introduction
The Thermo Scientific TSU Series Ultra-Low Temperature Freezers are designed for safe storage of biological samples at temperatures ranging from -50°C to -86°C. These freezers come with metal exterior cabinets that provide robust construction as well as aesthetically pleasing look. However, some users have reported experiencing an increase in internal temperature when adding additional metal cabinets to the existing freezer.
In this article, we will examine the key reasons why installing more metal cabinets to a Thermo Scientific TSU series freezer could potentially lead to a rise in internal temperature. We will also provide solutions and recommendations on how to add extra storage while maintaining the desired ultra-low temperatures inside the freezer.
Reasons for Temperature Increase with Additional Metal Cabinets
There are several factors that could contribute to an increase in temperature when extra metal cabinets are installed in a TSU series freezer:
1. Disruption of Air Circulation
Thermo Scientific TSU freezers utilize a cascade refrigeration system and fans to maintain uniform ultra-low temperatures throughout the freezer chamber. The cold air is circulated continuously to remove heat from stored samples.
Adding bulky metal cabinets inside the chamber can physically obstruct the cold air flow pathways. This disruption in air circulation results in formation of warm spots, leading to an overall increase in temperature.
2. Increase in Thermal Mass
The metal exterior construction of additional cabinets adds more thermal mass to the freezer. Thermal mass refers to the ability of a material to absorb and store heat energy.
More thermal mass means that the freezer now has to cool a larger metal surface area to reach and maintain the setpoint temperature. This puts extra load on the refrigeration system.
3. Introduction of Ambient Air
Installing more metal cabinets requires opening the main freezer door for extended periods of time. This allows significant amount of ambient air (at room temperature) to enter the freezer chamber.
Now the refrigeration system has to work harder to cool the large influx of warm air in addition to compensating for the added thermal mass. This can contribute to the temperature rise.
4. Condensate Buildup and Frost Accumulation
The entry of warm moist air also leads to excessive condensate and frost formation on the new cabinets and other interior surfaces. Buildup of condensate and frost acts as insulation and impedes heat transfer from within the freezer chamber.
This severely affects the ability of the refrigeration system to remove heat and maintain the setpoint low temperature.
5. Electrical Overload
Adding more metal cabinet units with lighting can overload the electrical circuit and trip the breaker. This leads to complete shutdown of the refrigeration system and quick rise in internal temperature.
Best Practices to Add Extra Storage
Follow these recommendations when installing additional metal cabinets to avoid temperature fluctuations in your TSU series freezer:
- Select cabinets made of non-heat conductive material – Opt for cabinets constructed frommaterials like polypropylene or ABS plastic instead of metal. This minimizes addition of thermal mass.
- Maintain sufficient air gap – Leave enough space between the cabinet rear and freezer walls for unobstructed air circulation through vents. Refer to manufacturer guidelines.
- Avoid blocking air vents or fans – Take care not to position the new cabinets directly in front of any interior air vents or circulation fans.
- Open door only when necessary – Limit the freezer door opening to the absolute minimum time required for installing the new cabinets. This lessens warm air influx.
- Allow for stabilization period – After installation, allow adequate time for the freezer to reach equilibrium at setpoint temperature before loading samples. This helps the compressor overcome the extra load.
- Check power requirements – Confirm that the additional lighting does not overload the electrical circuit. Upgrade circuit if needed.
- Use insulation support – Place the cabinets on raised supports made of thermal insulating material. This prevents excessive frost accumulation underneath.
- Check sample storage boxes – Ensure sample boxes and racks are made of thermally conductive material like aluminum to facilitate heat transfer to the refrigerated air. Avoid using any plastic containers or racks.
- Create a thermal map – Conduct a temperature mapping study before and after cabinet installation to identify any hotspots. Adjust sample loading accordingly.
Optimizing Sample Storage
Proper organization and arrangement of sample storage inside the ultra-low temperature freezer is vital for temperature stability. Here are some tips:
– Map out cold air flow
Strategically place samples along the cold air circulatory pattern inside the freezer chamber. Avoid putting samples directly in front of air vents.
– Maintain clearance between racks
Keep sufficient air gap between sample racks and walls to allow cold air to flow freely around the racks.
– Position samples uniformly
Distribute sample boxes evenly on racks at proper spacing. This prevents formation of cold spots.
– Avoid overloading
Do not exceed the maximum freezer load capacity. Overloading impedes air circulation.
– Use aluminum racks
Aluminum racks conduct heat better than plastic ones. This facilitates sample cooling.
– Store high-density samples across bottom racks
Place high-density sample boxes in bottom racks since cold air tends to sink. Top racks should hold lightweight samples.
– Avoid opening doors frequently
Limit access to freezer interior and open door only when necessary. Frequent door opening disrupts temperature stability.
Recommended Thermo Scientific TSU Freezer Models
Here are some top-rated Thermo Scientific TSU series ultra-low temperature freezers ideal for use with additional metal cabinet add-ons:
- Thermo Scientific TSU Series 702 – Has powerful cascading refrigeration system to handle extra cooling load.
- Thermo Scientific TSX Series – Utilizes advanced compressor technology and air balancing system to ensure temperature uniformity across increased storage space.
- Thermo Scientific TSUV Series – Equipped with dual refrigeration systems to provide temperature stability and fast recovery after door openings.
- Thermo Scientific TSU Series 600 – Designed with excellent sample temperature uniformity and low power consumption for energy efficiency.
Conclusion
The Thermo Scientific TSU line of ultra-low temperature freezers offers superb performance for stable long-term sample preservation at sub-zero setpoints. However, haphazard installation of additional metal cabinets in these units could disrupt air circulation and heat transfer leading to rise in internal temperatures.
Careful planning is required when increasing freezer storage capacity to prevent compressor overloading. With proper precautions and optimization of sample racks, users can safely enhance the storage space while maintaining the temperature stability needed for sensitive biological samples. Consult with the manufacturer if any major retrofitting of the TSU series freezers is required.
Frequently Asked Questions
Here are some common questions about the effects of adding metal cabinets on Thermo Scientific TSU series freezer temperature:
Q1: How much temperature rise can occur after installing extra metal cabinets?
The extent of temperature increase depends on multiple factors like the size, number and position of additional cabinets, ambient conditions, sample load, and freezer model. In optimal conditions, expect no more than 2-3°C rise from setpoint. But in worst cases, temperatures could increase by 5-10°C.
Q2: Should the compressor run time be increased to handle the extra load?
Increasing compressor runtime hours could help initially but is not recommended as a long-term solution. The ideal approach is to optimize air circulation, sample loading and insulation. Check that the compressor turns on at appropriate cabinet temperatures.
Q3: Can external chilling systems be added to counter the rise in temperature?
Yes, auxiliary cooling systems like Thermo Scientific’s Accel 500 Recirculating Chiller can be integrated to provide supplementary cooling capacity if the compressor alone is unable to maintain setpoint temperatures after installing additional cabinets.
Q4: How frequently should I check the freezer temperature after adding metal cabinets?
It is recommended to monitor and log the temperature at least twice daily for 1-2 weeks after cabinet installation. Temperature mapping of empty freezers should also be performed to identify hot spots.
Q5: Is it better to install all additional cabinets together or separately?
Ideally, the extra cabinets should be installed one at a time over multiple days. This allows the freezer to stabilize and overcome the incremental cooling loads. Simultaneous installation of multiple units causes drastic disruption.
Q6: Can I reconfigure the shelf layout to improve temperature stability?
Yes, you can experiment with different shelf arrangements, vary spacing between racks, adjust baffle positioning, and redirect air ducts & vents to optimize air circulation inside the freezer after adding cabinets.
In summary, take prudent measures when increasing storage capacity in TSU series freezers to ensure ultra-low temperatures are maintained throughout for sample integrity. Adequate preparation, vigilance and optimization is needed. Contact Thermo Fisher Scientific support for guidance on safely adding more metal cabinets without temperature fluctuations.