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Pressure and Temperature Symptoms Chart

This document contains a Pressure and Temperature Symptoms Chart.

Product line:
All Cooling Units.

All Product models, all serial numbers.

The purpose of this document is to provide a clear communication on what the relationship between pressure, temperature, and the use of Superheat and Subcooling to troubleshoot.


Pressure and Temperature Symptoms Chart:
Symptoms Exhibited *Condition Solutions
SymptomPossible Solutions
Light loadCheck filter, blower speed tap selected, blower motor, wheel, and capacitor.
Insufficient refrigerant charge; undercharge; leakCheck system for leak(s). Recover refrigerant, repair leak(s), evacuate system to 500 microns, and re-charge with refrigerant.
-Restriction in refrigerant circuitLook for significant temperature difference at point of restriction. Possible incorrect orifice pin (too small) or TXV stuck closed.
Heavy loadDue to excessive air flow across coil or open return duct in unconditioned space. Check blower speed tap setting (too high) and return duct for leakage.
Restricted outdoor coilInsufficient air flow across Condenser coil. Check cleanliness of coil. Check condenser fan motor, blade, and capacitor.
Excessive refrigerant charge; overchargeRecover refrigerant from system and weigh in refrigerant
Air and/or Non-condensable in systemRecover refrigerant from system, evacuate system to 500 microns, and weigh in refrigerant.
-Over feeding Metering deviceCheck for proper pin size or loose TXV sensing bulb or TXV stuck open.
-Compressor defectiveI.E. runs but doesn't pump, abnormally low Amp draw and abnormally high compressor temperature may be indicated.
* "Normal" refers to Pressures, Temperatures, and/or values obtained at rated air flow under a given set of conditions and assumes that no changes have been made to factory refrigerant charge.

APC Greece


Pressure and Temperature Symptoms Chart Rev. 20111128.pdfPressure and Temperature Symptoms Chart Rev. 20111128.pdf [667.27 KB]
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