CSZ ZP 16, Installation, Operation & Maintenance Manual, Page: 36 / 88

GENERAL DESCRIPTION
Page 2-20
When there is a call for cooling 3-SOL (and possibly 2-SOL, if 3-SOL has been energized for more than thirty
seconds) is energized. When the chamber is near the set point the controller begins to cycle 3-SOL on and
off. At the same time the R-508B hot gas by-pass solenoid (5-SOL) is cycling on and off opposite of 3-SOL. If
the controller does not call for cooling for sixty seconds the refrigeration system will turn off.
Mode: Humidity (Optional Equipment)
In humidity mode the unit runs as a single stage system. The R-404A compressor turns on. A high pressure
switch (1-PS) will turn the compressor off if a high discharge pressure is reached. Contact Cincinnati Sub-
Zero’s service department if this occurs.
When cooling is called for, solenoid H-1 SOL is energized allowing refrigerant to fl ow to the evaporator coil.
When the chamber is near the dry bulb temperature set point, the controller begins to cycle H-1 SOL on and
off. When Dehumidi
fi cation is called for, solenoid H-11 SOL is energized allowing refrigerant to fl ow to the wet
coil. When humidity is called for, solenoid H-11 is de-energized.
Mode: Pumpdown
When the conditioning system is turned OFF, refrigeration system 1 will go into pumpdown mode.
In pumpdown mode, the System 1 compressor will automatically turn on when pressure in the suction line
is above 25 psig. The compressor turns off when the suction line pressure is reduced to 5 psig. Pressure
Switch 7-PS will monitor the suction line pressure and control the operation of the compressor in pumpdown
mode. The liquid line solenoid valve 1-SOL (or valves 1 & 7-SOL for 10 hp and larger), and the R-404A hot
gas solenoid will not be energized. Pumpdown forces most of the refrigerant into the high side of the system.
The refrigerant will be in the liquid line,
fi lter-drier, sight glass, condenser and discharge line. Pumpdown
serves to protect the compressor on start-up. If there was no pumpdown, a slug of liquid refrigerant could exit
the cascade condenser and damage the compressor.
TUNDRA
®
DESCRIPTION
(Refer to Refrigeration Diagram in Drawing Section)
The compressor (item 1) will pump compressed refrigerant vapor through the discharge line where the high
pressure gauge displays the pressure of the refrigerant. The high pressure switch (item 95) senses the
discharge refrigerant pressure and will open a contact in the event that discharge pressure exceeds 400 psig
(27.6 bar(g)). This contact opening will serve to shut down the unit and will automatically reset when the
pressure drops to 325 psig (224 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. A relief valve is
installed near the condenser and will relieve at 450 PSIG (310 bar(g)).
The condenser (item 5) cools the high pressure refrigerant vapor and condenses it into a high pressure liquid.
The condenser is either air-cooled or water-cooled. If the unit is air-cooled, the condenser fan motor (item 96)
will be energized anytime the system is running. If the unit is water-cooled, the discharge pressure regulator
(item 7) will maintain the discharge pressure at approximately 250 PSIG (17.2 bar(g)).
High pressure liquid refrigerant exits the condenser and passes a service port. The liquid fl ows through a
receiver (water-cooled units only), 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 where the refrigerant is evenly distributed to the evaporator
circuits. The evaporator (item 52) serves to boil the rest of the refrigerant 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 refrigerant vapor exits the evaporator and moves through the suction line. A service valve is
located near the compressor.