Service Diagnosis - Scotsman NME650R Service Manual

NME650R
SERVICE DIAGNOSIS: Condition - No Ice Being Produced
A. Check: Voltage to the unit, restore it if there is none. Compare to the nameplate.
B. Check: The master switch, switch ON if off.
C. Check: The reset switch (high pressure): depress and release the switch. If the unit still does
not start, check the high side pressure.
D. Check the high pressure cut out switch.
1. This pressure switch opens at 450 psig. Check the high side pressure, reset the switch and observe that
the fan is forcing air through the condenser. If the switch opens at pressures below 450 psig, replace the
switch. If the pressures rise above the trip out point, and the unit shuts down:
a. Check for adequate air flow. Clean the condenser. If the air flow is poor because of the
installation, advise the user that the unit should be moved, or the air around it kept cooler.
Check the fan motor for tight bearings and proper rotation.
Check that the fan blades are clean, and the fan secure to the fan motor shaft.
b. Check the head pressure control valve, it should be maintaining a head pressure
above 180 psig. If the unit has the correct charge, and the condenser is clean, and the
refrigerant lines are not kinked or twisted, and the condenser is not overheated by
external heat loads, the head pressure should be under the trip out point of the head
pressure control switch. If all of the above are found to be good, and the machine
trips out on high head pressure, replace the head pressure control valve.
E. Check the water level. If there is not enough water in the reservoir, the water level sensor will
keep the machine from starting.
a. Check the water level, restore/adjust if low.
b. Check the water level sensor, clean if dirty, (see maintenance).
c. Check the circuit board, see next page.
If the machine does not start, see the next page.
STATUS: NOTHING OPERATES
June 1994
Page 24