Scotsman ND750 Service Manual page 21

ND750
SERVICE DIAGNOSIS: Condition - Low Ice Production
STATUS: EVERYTHING IS OPERATING
A. Check the air cooled condenser for dirt. Clean as required. Check the head pressure on water
cooled. Adjust as required. If the head pressure is very high:
1. Air cooled. Check for high air temperatures, or restrictive air flow. Correct as needed.
2. Water cooled. Check for high water temperatures, or low water pressure.
Correct as needed.
3. The refrigerant may contain non condensable gases, purge, evacuate, and recharge per
nameplate.
B. Check the evaporator
1. Clean the evaporator, the mineral build up will adversely affect the ice machines production.
2. Check the evaporator for water leaks, replace the water seal if found to be leaking.
3. Check the low side pressure; normal is about 30 psig. If low, assume a refrigerant leak,
locate, repair and recharge.
If no leak, the TXV may be restricted, defective or not adjusted properly. If needed,
replace the TXV, evacuate, and recharge per nameplate.
4. Check the insulation on the evaporator. It should be dry, with no wet spots or frost.
If the insulation has failed: replace the evaporator or add extra insulation in the form
of foam tape to the evaporator.
C. Check the compressor.
1. The compressor may be inefficient.
a. Check the amp draw, if low change the compressor.
b. if the amp draw is normal, pinch off the suction line to check the pull down capability
of the compressor. The compressor should pull down to 25 inches of vacuum and hold
there for three to five minutes.
January, 1989
Page 21