Service Diagnosis: Refrigeration And/Or Mechanical - Scotsman CME650R Service Manual

SERVICE DIAGNOSIS: Refrigeration and/or Mechanical

SYMPTOM
Poor harvest
Unit cycles off during freeze or
harvest
Low capacity
Unit shuts off before bin is full
Compressor cycles on and off
Frost on compressor
POSSIBLE CAUSE
Hot gas valve does not open
Head pressure control valve does
not maintain enough head
pressure.
Hi temperature switch opens and
closes
High head pressure, from dirty
condenser, faulty fan motor
Non condensable gas in the
system
Extreme hot location
Overcharge of refrigerant
Hot gas valve leaks thru
Liquid and discharge lines are in
contact with each other
Bin thermostat adjusted to open
too soon.
Low pressure control opening and
closing
Compressor overheats
Some frost will not hurt
TXV meters too much refrigerant
October 1994
Page 25
CME650R
PROBABLE FIX
Check for power to the coil, check
for not opening, replace
Replace head pressure control
valve.
Hot gas valve leaks thru, replace it
Clean condenser, repair fan
motor
Purge system, evacuate and
weigh in nameplate charge
Relocate the cabinet
Evacuate and weigh in nameplate
charge
At the end of the freeze cycle
there should be frost on the
evaporator end of the hot gas
tubes, if not replace the hot gas
valve
Separate and insulate them
Rotate knob on the thermostat
clockwise to a colder setting.
Check low side pressure, liquid
line valve must open and low side
pressure raise over 35 PSIG
before pump down control will
close to run compressor
TXV not letting enough refrigerant
into evaporators, adjust or
replace TXV
Mechanical fault with compressor,
replace compressor
Do nothing
Adjust or replace TXV