Thermo Scientific MR05 Series

Questions and Answers

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Jonathan WalkerAug 25, 2025
Why does Thermo Scientific MR05 compressor start, but not switch off of start winding?
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  Robyn AveryAug 25, 2025
  If the compressor in your Thermo Scientific Refrigerator starts but doesn't switch off the start winding, it could be due to several reasons. Begin by checking for low voltage to the unit and correct it. Then, inspect the run and start capacitors, replacing them if they have failed or are incorrect. A faulty start relay could also be the cause, so replace it if necessary. Additionally, check the motor for any electrical issues such as open windings, short circuits, or burnouts. In some cases, internal mechanical trouble within the compressor may be the problem, requiring a compressor replacement. Finally, verify that the wiring is correct by checking it against the wiring diagram. Excessively high discharge pressure can also cause this issue.
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Jeffrey SmithAug 26, 2025
Why does Thermo Scientific MR05 compressor run long or continuously?
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  Brian EscobarAug 26, 2025
  If your Thermo Scientific Refrigerator's compressor is running long or continuously, several factors could be responsible. Start by checking for a shortage of refrigerant and look for any leaks. If found, repair them. The control contacts might be stuck or frozen, so try cleaning them or replacing the control. An excessive load in the refrigerated air space could also cause this, so determine the reason and correct it. Additionally, a dirty condenser can lead to continuous running, so clean the condenser. If the evaporator coil is iced, defrost it and check the defrost circuit. A restriction in the refrigeration system may also be the reason, so determine its location and remove it. Finally, ensure the evaporator fan motors are running and check the door switch.
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Sonya BakerAug 28, 2025
What to do if Thermo Scientific Refrigerator compressor hums but trips on thermal overload?
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  edgarriveraAug 28, 2025
  If the compressor in your Thermo Scientific Refrigerator will not start, but hums and trips on thermal overload, several issues may be the cause. First, check for low voltage to the unit and correct it. Then, inspect the start capacitor and run capacitor, replacing them if they have failed or are incorrect. A faulty start relay could also be the cause, so replace it if necessary. Additionally, check the motor for any electrical issues such as open windings, short circuits, or burnouts. In some cases, internal mechanical trouble within the compressor may be the problem, requiring a compressor replacement. Finally, verify that the wiring is correct by checking it against the wiring diagram. Excessively high discharge pressure can also cause this issue.
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Craig IbarraAug 30, 2025
Why is Thermo Scientific Refrigerator compressor noisy or vibrating?
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  whitepamelaAug 30, 2025
  If the compressor in your Thermo Scientific Refrigerator is noisy or vibrating, several factors could be the cause. Start by checking for flooding of refrigerant into the crankcase, and inspect the expansion device and refrigerant charge. Improper piping support can also cause noise, so relocate tubing or add hangers. A worn compressor can also be noisy, so consider replacing it. Look for any loose parts or mounting and tighten them. Lastly, check the condenser fan blade for looseness or obstructions and repair as needed.
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tfergusonAug 31, 2025
Why does Thermo Scientific MR05 compressor short cycle on temperature or pressure controls?
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  Marc WestSep 1, 2025
  If your Thermo Scientific Refrigerator's compressor starts and runs, but short cycles on temperature or pressure controls, consider these possible causes: The differential may be set too close, so try widening it. High discharge pressure, and low discharge pressure can also cause short cycling.
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Samuel DixonSep 2, 2025
Why is ice accumulating on the ceiling of my Thermo Scientific MR05?
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  kthompsonSep 2, 2025
  If you notice ice accumulating on the ceiling around the evaporator and/or on the fan guards or blades in your Thermo Scientific Refrigerator, there are several potential causes. The defrost duration might be too long, so adjust the defrost termination. The fan delay might not be delaying the fans after the defrost period, indicating a defective fan delay thermostat that needs replacement. A defective timer could also be the issue, requiring replacement. Finally, there might be too many defrost cycles per day, so adjust the timer for fewer defrost cycles.
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Raymond DanielsSep 4, 2025
Why is the suction line frosted on my Thermo Scientific MR05 Refrigerator?
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  Kathryn MccartySep 5, 2025
  If the suction line of your Thermo Scientific Refrigerator is frosted or sweating, several issues could be the cause. The expansion valve may be passing excess refrigerant or is oversized, so readjust the valve or replace it with a smaller one. The expansion valve could also be stuck open, in which case you should clean the valve of foreign particles and replace it if necessary. Ensure the evaporator fan motors are running, checking the door switch. Finally, the system may be overcharged with refrigerant, so correct the charge.
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Vanessa SerranoSep 6, 2025
Why is evaporator coil not clearing of frost during defrost cycle in Thermo Scientific Refrigerator?
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  mariadeanSep 6, 2025
  If the evaporator coil in your Thermo Scientific Refrigerator is not clearing of frost during the defrost cycle, several factors could be responsible. The coil temperature may not be getting above the freezing point during defrost, so check the heater operation or hot gas solenoid valve. There might not be enough defrost cycles per day, so adjust the timer for more defrost cycles, or the defrost cycle might be too short, so adjust the timer for a longer defrost cycle. A poor door seal can also contribute to this issue, so adjust the door latch and install a new gasket. Finally, a defective timer or defrost thermostat could be the cause, requiring replacement of the defective component.
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Ryan ScottSep 8, 2025
What causes high suction pressure in Thermo Scientific Refrigerator?
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  Nicholas MartinezSep 8, 2025
  If you are experiencing high suction pressure in your Thermo Scientific Refrigerator, there are two primary causes to consider: The unit may be experiencing an excessive load, in which case you should reduce the load or add additional equipment. Alternatively, the expansion valve may be overfeeding, so check the remote bulb and adjust the superheat.
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Michael AnthonySep 10, 2025
Why is ice accumulating in the drain pan of my Thermo Scientific MR05?
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  Dwayne MillsSep 12, 2025
  If you're seeing ice accumulating in the drain pan of your Thermo Scientific Refrigerator, several issues could be the cause. The heater may be defective, so replace it. The unit may not be pitched properly, so check and adjust if necessary. The drain line could be plugged, so clean it. A defective drain line heater could also be the problem, so replace the heater. Poor contact between the drain pan and heater element can also cause ice accumulation, so repair it. Finally, a defective timer or defrost thermostat could be the cause, so replace the defective component.

The Thermo Scientific MR05 Series Undercounter Laboratory Refrigerators are designed for general purpose laboratory use, providing reliable temperature control for storing non-flammable general laboratory products. These units are not intended for use as medical devices or for in vitro diagnostic cases, nor are they approved for the storage of blood, blood products, or flammable materials.

Function Description

The MR05 series refrigerators are complete packaged units, ready to operate once plugged into an electrical source. They feature a control system that maintains a preset cabinet temperature, typically 4°C, with an optional 5°C setpoint available. The temperature is displayed digitally with 1°C resolution, allowing for precise monitoring. The refrigeration system utilizes CFC-free refrigerant and CFC-free foamed-in-place urethane insulation, contributing to environmental responsibility and efficient thermal retention. Quiet, hermetically sealed refrigeration compressors ensure reliable and unobtrusive operation.

The defrosting process is primarily automatic, accomplished by air circulation during off-cycle periods. Under normal conditions, temperature warm-up during defrost is virtually unnoticeable, though an occasional 2°C warm-up may occur with heavy usage or extreme ambient conditions.

Usage Features

The MR05 refrigerators are designed for indoor use only and are optimized for performance in a 20°C operating environment. Installation in unheated areas may require a low-temperature compressor protection kit for satisfactory operation. The cabinet is designed to pass through a standard 30-inch door opening, facilitating placement in various laboratory settings.

For optimal performance, the cabinet should be moved into its desired location and ensured that the bottom is evenly supported. Thin shims can be used to equalize weight distribution and prevent rocking or vibration when the condensing unit operates. It is crucial to ensure the front grill is unobstructed to allow for proper airflow.

The unit is shipped in a ready-to-operate condition, meaning adjustment of operating temperatures or setpoints is generally not necessary and could adversely affect performance. After installation, the unit should be operated for several hours to allow the cabinet to reach normal operating temperatures before any products are stored.

For temperature sensing cables, rear access ports should be utilized instead of the front door gasket to maintain seal integrity. The door is equipped with keyed locks for security.

The controller operations include various settings and parameters that can be adjusted, though it is recommended to consult a qualified service technician for any questions regarding settings to avoid changing unit performance. The controller allows for viewing of the target set point, initiating a manual defrost, and accessing programming modes for advanced adjustments. It also provides error messages and alarms for various conditions such as room temperature probe failures, evaporator probe failures, and compressor issues, aiding in troubleshooting.

Maintenance Features

Regular maintenance is essential for the longevity and optimal performance of the MR05 refrigerator. The cabinet interior should be cleaned frequently, with any spilled liquid wiped off immediately. A mild detergent and lukewarm water or a solution of bicarbonate of soda (1 tablespoon per gallon of water) is recommended for cleaning the interior and exterior surfaces, which should then be rinsed and thoroughly dried. Shelves and/or drawers should be removed for thorough scrubbing, and door gaskets should be cleaned periodically with water.

The unit cooler fan operates continuously when the door is closed and does not require lubrication. The cooling coil automatically defrosts during the condensing unit's off cycle, eliminating the need for manual defrosting.

The condensing unit does not require oil or other lubrication. However, the finned condenser can become clogged with lint or dust and should be kept clean. A vacuum cleaner or a small test tube brush can be used for this purpose annually. Failure to keep the condenser fins free of dirt and lint can hamper operation and potentially damage the refrigeration system.

An annual inspection of the mechanical refrigeration equipment by a qualified service provider or factory direct technician is recommended. If the refrigeration system is opened for any reason, extreme care must be taken to prevent moisture-bearing air from entering, and a new drier should be installed in the lines when the system is closed.

The condensate evaporator pan, located behind the compressor fan and base grill, should be cleaned at least once a year to ensure proper drainage and prevent buildup.

The manual also provides detailed instructions for hinge and latch adjustments, which may be necessary if the door does not align properly or the latch does not seat correctly. These adjustments help maintain a proper gasket seal, crucial for temperature stability. In case of door gasket replacement, the manual outlines the steps to remove the old gasket, clean the mounting track, and install a new one, ensuring a tight seal.

Troubleshooting charts are included to assist in diagnosing and resolving common issues, such as the compressor not starting, humming, or running continuously, high or low discharge pressure, and ice accumulation. These charts provide possible causes and corrective steps, guiding users or technicians through the diagnostic process.