Greenheck MPX (472695) - Manual (Page 35)

Always have a completed Pre Start-Up Checklist, Unit Start-Up Checklist and Optional Accessories Checklist prior to
requesting parts or service information.
Symptom Possible Cause Corrective Action
Suction line
is frosting
Insufficient evaporator airflow.
Check airflow, check filters, check drive for loose parts
or belts.
Malfunctioning or defective expansion
valve.
Check bulb of thermal expansion valve.
Frost on
evaporator
coil
Hot gas bypass valve not functioning
properly.
Check valve. If defective, replace.
Manual hot gas bypass valve closed. Open valve.
Low load or airflow. Increase airflow, check filters.
Troubleshooting – Refrigeration Circuit
35 Model MPX Make-Up Air Unit
®