Ice-O-Matic EMF Series - Manual (Page 48)

Flake Ice Machines Refrigeration System
Page F7
Expansion Valve
The expansion valve meters the flow of refrigerant into the evaporator, changing its state
from a high pressure liquid to a low pressure liquid. This drop in pressure causes the
refrigerant to cool. The cooled refrigerant absorbs heat from the water in
the evaporator.
The flow of refrigerant into the evaporator is controlled by the temperature
at the outlet of the evaporator. The expansion valve bulb, which is mounted
to the top of the suction line, senses the evaporator outlet temperature
causing the valve to open or close. As ice forms in the evaporator the
temperature drops and the flow of refrigerant into the evaporator decreases.
The evaporator should become completely flooded (filled with liquid
refrigerant). A completely flooded evaporator will form ice in the entire
evaporator. A starved evaporator (not enough liquid refrigerant) will have poor or no ice
formation in the evaporator, and the tube exiting the evaporator will not frost.
The tubes in and out of the evaporator should frost within approximately 5 minutes from the
time the compressor starts. An expansion valve that is restricted or not opening properly will
starve the evaporator causing the suction pressure to be lower than normal. Wet ice or slow
production will result.
A low refrigerant charge will also starve the evaporator and cause low
suction and discharge pressure. It is important that the refrigerant charge
be correct before diagnosing the valve. If not sure of the amount of
charge in the system, the refrigerant should be recovered and the correct
charge weighed in. If the evaporator is starved but the suction pressure is
higher than normal, the compressor may be inefficient.
If the expansion valve sticks open or if the bulb is not making contact with
the suction line, the flow of refrigerant into the evaporator will be too great
and liquid refrigerant will flood back to the compressor. The evaporator
temperature will be higher than normal resulting in wet ice and slow
production.
A dual evaporator machine has one expansion valve for each evaporator. If one valve sticks
open and the other is operating normally, the suction pressure will be higher than normal and
the evaporator with the defective expansion valve will produce less ice than the side with the
good valve. If one expansion valve sticks closed and one is operating normally, the suction
pressure will be normal or low and the evaporator with the defective expansion valve will
produce less ice than the side with the good valve.
Important!
Use only ICE-O-Matic O.E.M. replacement expansion valves. Warranty will be void if
an expansion valve other than the correct ICE-O-Matic replacement part is used.