Manitowoc STH042 4/16, Technician'S Handbook

Page: 93 / 146

Part Number STH042 4/16 93
Final Analysis
The column with the highest number of check marks
identifies the refrigeration problem.
Column 1 – Harvest Valve Leaking
A leaking harvest valve must be replaced.
Column 2 – Low Charge/TXV Starving
Normally, a starving expansion valve only affects the
freeze cycle pressures, not the harvest cycle pressures. A
low refrigerant charge normally affects both pressures.
Verify the ice machine is not low on charge before
replacing an expansion valve.
Add refrigerant charge in 2 oz. increments as a diagnostic
procedure to verify a low charge. (Do not add more
than the total charge of refrigerant). If the problem is
corrected, the ice machine is low on charge. Find the
refrigerant leak.
The ice machine must operate with the nameplate
charge. If the leak cannot be found, proper refrigerant
procedures must still be followed. Change the liquid
line drier, evacuate the system and weigh in the proper
charge.
If the problem is not corrected by adding charge, the
expansion valve is faulty.
Column 3 – TXV Flooding
A loose or improperly mounted expansion valve
bulb causes the expansion valve to flood. Check bulb
mounting, insulation, etc., before changing the valve.
Column 4 – Compressor
Replace the compressor and start components. To
receive warranty credit, the compressor ports must be
properly sealed by crimping and soldering them closed.
Old start components must be returned with the faulty
compressor.