Why does my test chamber have a slow pull-down or no pull-down at all?

A test chamber's pull-down rate can be affected by a variety of things including the compressor and the condenser in the unit.

Check out these possible causes and solutions when your compressor and condenser fan run continuously, and the compressor amperage is normal:

Your test chamber's evaporator coil has iced up
      SOLUTION: Defrost and dry out your test chamber. Remember to plug up ports or any openings where external air can enter the chamber.
There is an excessive live load in the test chamber, or there is excessive heat leakage into the chamber through the ports or other openings is occurring.
      SOLUTION: Eliminate the cause.
The door is being opened too often.
      SOLUTION: Eliminate the cause.
There is a leak and consequent loss of refrigerant charge.
      SOLUTION: Identify and repair the leak. Then recharge the test chamber with refrigerant.
The compressor is defective.
      SOLUTION: Replace the defective compressor.
A test piece of the specimen is blocking the airflow in the test chamber.
      SOLUTION: Remove any excess load or relocate the specimen.


Check out these possible causes and solutions during compressor overload, or when the compressor cycles on and off.

The condenser is dirty, which is restricting the airflow.
      SOLUTION: Clean the condenser, or move the test chamber so that there is free airflow across the condenser and out the side of the chamber.
The ambient temperature in the room is too high.
      SOLUTION: Make sure that the test chamber is located in a well-ventilated area where the temperature is normal.
The condenser fan is not operating correctly.
      SOLUTION: Try tightening the fan blade. Replace the motor or repair as necessary.
The condenser fan is not running or operating at the rated RPM.
      SOLUTION: Repair or replace the condenser fan motor.
The temperature controller setpoint is out of adjustment.
      SOLUTION: Use your test chamber's instruction manual to correct the adjustment.
The refrigerant line is damaged or restricted.
      SOLUTION: Identify any damage or restriction and correct it.
The test chamber is running on low voltage or worn relay contacts.
      SOLUTION: Correct the low volume condition and/or replace the relay.


Check out these possible causes and solutions on low-temperature cutout, or when the compressor cycles on and off.

The test chamber's temperature is too low to permit running mechanical refrigeration.
      SOLUTION: Increase the temperature inside the test chamber above +10°F.
The low-temperature cutout control is defective or out of adjustment.
      SOLUTION: Adjust, replace, or repair the low-temperature cutout control.


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