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November Tech Challenge – Answer

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A logo of a yellow, red, blue, and green rubix cube with one square out of place and "Tech Challenge" written beneath it

A freezer utilizing R-402A with a TXV metering device (and receiver) has a customer complaint of “warm case.” The symptoms at the store confirm that the case that normally operates about 0 degrees is 32 degrees and the condensing unit is running continuously. What are the “possible causes” (note: there is only one problem intended) with the following measured conditions on this field service check sheet? 

Answer: The possible cause appears to be an inefficient compressor. The head pressure is lower and the suction pressure is higher than normal with a very high discharge temperature caused by the recompression of gases. The TXV is wide open, but there is very low refrigerant flow causing maximum subcooling (to within 2 deg. of ambient) and high superheat. The amps are low because the compressor isn’t working. A compressor efficiency check per manufacturers’ specifications needs to be accomplished. 

Posted In: Tech Challenge

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