GENERAL DESCRIPTION
38
Chamber Cooling
After passing the bypass tee, the liquid refrigerant flows through the liquid line solenoid (item 110) and
into the thermostatic expansion valve (item 111) 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 112), where the refrigerant is evenly distributed to evaporator
circuits. The evaporator (item 113) serves to boil the rest of the R-404A into a vapor. This boiling action
cools the chamber. If dehumidification is called for, some of the R-404A refrigerant is diverted to the
humidity loop prior to entering the thermostatic expansion valve (see humidity description).
Humidity Loop (Optional Equipment)
When dehumidification is called for, some of the liquid refrigerant is diverted to the humidity loop. The
refrigerant passes through the wet coil solenoid valve (item H127) and a wet coil capillary tube (item
H123). Two phase refrigerant exits the capillary tube and enters the evaporator (item H125). The
evaporator is cold enough to attract moisture from the chamber air, but not cold enough to freeze
water on the evaporator. The temperature of the evaporator is regulated by an evaporator pressure
regulator valve (E.P.R) (item H126) and is intended to be a flooded 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.
If the chamber is equipped with a Low RH package, the following description applies. When
dehumidification is called for, some of the liquid refrigerant is diverted to the humidity loop. The
refrigerant passes through a solenoid valve (item H131) and a Low RH thermostatic expansion valve
(item H130). Two phase refrigerant exits the thermostatic expansion valve and enters the evaporator
(item H125). The evaporator temperature is cold enough to freeze water out of the air where it collects
and freezes on the surface of the evaporator. The temperature of the evaporator is able to drop below
freezing temperature due to the suction bypass solenoid (item H129) where it allows the suction vapor
to bypass the evaporator pressure regulator valve (item H126). This allows the chamber to achieve low
temperature dew points limited, as previously discussed in this manual.
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 117) and the hot gas bypass regulator
valve (item 118). The liquid inject line consists of a liquid injection solenoid valve (item 121) and liquid
injection thermostatic expansion valve (item 123). The hot gas bypass solenoid valve (item 117) will
open and close opposite of the liquid line solenoid valve (item 110). The 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 will sense the temperature
of the suction gas, and 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.
Содержание ZP Series
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