Cincinnati Sub-Zero ZP Series, Installation, Operation & Maintenance Manual, Page: 42 / 104

GENERAL DESCRIPTION
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Chamber Cooling (2 HP – 6 HP Systems)
After passing the bypass tee, the liquid refrigerant flows through the liquid line solenoid (item 210) and
into the thermostatic expansion valve (item 211) where it changes to a low pressure, two phase
refrigerant. The two phase refrigerant is cold due to the flashing of refrigerant. The two phase
refrigerant enters the distributor (item 212) where the refrigerant is evenly distributed to evaporator
circuits. The evaporator (item 213) serves to boil the rest of the R-508B/R-23 into a vapor. The boiling
action cools the chamber. Superheated R-508B/R23 refrigerant vapor exits the evaporator and moves
through the suction line. A suction service valve (item 215) is located near the compressor.
(6 HP systems) The low pressure switch (item 298) senses the pressure of the vapor. If the pressure is
below 10“ hg vacuum, it will open a contact and shut the system down. It will automatically reset
when the pressure rises to an acceptable level. A low pressure gauge (item 282) indicates the
pressure in the line. A suction service valve (item 215) is located near the compressor.
Chamber Cooling (10 HP – 20 HP Systems)
After passing the bypass tee, the liquid refrigerant flows through the maximum liquid line solenoid (item
210) and into the maximum thermostatic expansion valve (item 211) where it changes to a low pressure,
two phase refrigerant. In parallel with maximum valve, liquid refrigerant flows through a minimum
liquid line solenoid (item 219) and into the minimum thermostatic expansion valve (item 220) where it
also changes to low pressure, two phase refrigerant. The two phase refrigerant is cold due to the
flashing refrigerant. The two phase refrigerant enters the distributor (item 212) where the refrigerant is
evenly distributed to evaporator circuits. The evaporator (item 213) serves to boil the rest of the R-
508B/R-23 into a vapor. The boiling action cools the chamber. Superheated R-508B/R23 refrigerant
vapor exits the evaporator and moves through the suction line. A suction service valve (item 215) is
located near the compressor.
Bypass Loop (R508B Systems)
The discharge refrigerant vapor passes a tee where some of the vapor is diverted to the suction line
through a hot gas bypass regulator valve (item 263). The hot gas bypass regulator valve will allow hot
discharge refrigerant vapor to flow directly to the suction line. This is done as a means to control
cooling capacity or to “unload” the system. The liquid injection thermostatic expansion valve (item
261) will sense the temperature of the suction gas, and automatically open to feed liquid refrigerant
into the suction line. This will provide cooling for the hot gas that is being fed into the suction line.
The cooling effect keeps the compressor from overheating. There is also a discharge temperature
control valve (item 278), which prevents the compressor from overheating and results in no loss of
capacity or mass flow.