CSZ ZP 16, Installation, Operation & Maintenance Manual, Page: 38 / 88

GENERAL DESCRIPTION
Page 2-22
SINGLE STAGE - SYSTEM 1 (R-404A) DESCRIPTION
Refer to Refrigeration Diagram in Drawing Section
The compressor (item 1) will pump compressed R-404A vapor through the discharge line where the high
pressure gauge displays the pressure of the refrigerant. The high pressure switch (item 95 or item 100)
senses the discharge refrigerant pressure and will open a contact in the event that discharge pressure
exceeds 350 psig (24.1 bar(g)). This contact opening will serve to shut down the unit and will automatically
reset when the pressure drops to 250 psig (17.2 bar(g)). The discharge refrigerant vapor passes a tee which
diverts some of the refrigerant to the bypass loop (see bypass description), and enters the condenser.
The condenser (item 5) cools the high pressure R-404A vapor and condenses it into a high pressure liquid.
The condenser is either air-cooled or water-cooled. If the condenser is air-cooled, the condenser fan motor
(item 96) will be energized anytime System 1 is running. If the unit is water-cooled, the discharge pressure
regulator (item 7) will maintain the discharge pressure at approximately 250 PSIG (17 bar).
The liquid fl ows through a receiver, fi lter-drier, sight glass, liquid line solenoid (item 49) and into the T.E.V.
(item 50) where it changes to a low pressure two-phase refrigerant. The two phase refrigerant is cold due to
the
fl ashing of refrigerant. It enters the distributor (item 51) where the refrigerant is evenly distributed to the
evaporator circuits. The evaporator (item 52) serves to boil the rest of the R-404A into a vapor. This boiling
action cools the chamber. If humidity is called for, some of the R-404A refrigerant is diverted to the humidity
loop prior to entering the T.E.V. See humidity section for description.
Superheated R-404A vapor exits the evaporator and moves through the suction line. A service valve is
located near the compressor.
Humidity Loop (Optional Equipment)
When humidity is called for, some of the liquid refrigerant is diverted to the humidity loop. The refrigerant
passes through a solenoid valve (item H27) and a wet coil capillary tube (item H23). Two phase refrigerant
exits the capillary tube and enters the wet coil (item H25). The wet coil is cold enough to attract moisture from
the chamber air, but not cold enough to freeze the water on the coil. The temperature of the coil is regulated
by a pressure regulating E.P.R. valve (item H26) and is intended to be a
fl ooded coil by design. The warm
chamber air keeps the moisture from freezing on the coil. After the refrigerant leaves the wet coil, it enters the
suction line and returns to the compressor.
Bypass Loop - The bypass circuit is composed of two lines in parallel. The Hot Gas Bypass Line, and the
Liquid Injection Line. The hot gas bypass line consists of a solenoid valve (item 17) and Hot Gas Bypass
Regulator (item 18). The liquid injection line consists of a Liquid Injection Solenoid (item 21) and Liquid
Injection T.E.V. (item 23). The hot gas bypass solenoid (item 17) will open and close opposite of the liquid
line solenoid (item 49). It will allow hot discharge refrigerant vapor to
fl ow directly to the suction line. This is
done as a means to control cooling capacity or to “unload” the system. The liquid injection T.E.V. will sense
the temperature of the suction line. It will open automatically 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.