Refrigeration System Malfunctions Troubleshooting – Trane Commercial HVAC Help Center

Refrigeration System Malfunctions
and Probable Causes Troubleshooting Guide

Refrigeration System Malfunctions and Probable Causes
Probable Cause	Head Pressure	Suction Pressure	Compr Amp Draw	Superheat	SubCool	Air Temp Diff.	Water Temp. Diff.
Undercharged system (leak)	Low	Low	Low	High	Low	Low	Low
Overcharge system	High	High	High	Low	High	High	High
Low Air Flow (heating)	High	High	High	Low	Low	High	Low
Low Air Flow (cooling)	Low	Low	Low	Low	High	High	Low
Low Water Flow (heating)	Low	Low	Low	Low	High	Low	High
Low Water Flow (cooling)	Low	High	High	High	Low	Low	High
High Air Flow (heating)	High	Low	Low	Low	High	Low	High
High Air Flow (cooling)	Low	High	High	High	Low	Low	High
High Water Flow (heating)	High	High	High	High	Low	High	Low
High Water Flow (cooling)	High	Low	Low	Low	High	High	Low
Low Indoor Temperature (heating)	Low	Low	Low	High	High	High	High
Low Indoor Temperature (cooling)	Low	Low	Low	Low	High	Low	Low
High Indoor Temperature (heating)	Low	High	High	High	Low	Low	High
High Indoor Temperature (cooling)	High	High	High	High	Low	Low	High
Restricted Filter/Drier	High	Low	High	High	Low	Low	Low
Inefficient Compressor	Low	High	Low	High	High	Low	Low
TXV – No Bulb Charge	Low	Low	Low	High	High	Low	Low
Plugged Cap Tube	Low	Low	Low	High	High	Low	Low
Scaled Heatexchanger (htg)	Low	Low	Low	Low	High	Low	Low
Scaled Heatexchanger (clg)	High	High	High	High	Low	Low	Low
Equalizer Line is Piped to Water Reg Valve	Works in the heating mode, but in the cooling mode, it pumps down the suction.

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