GENERAL DESCRIPTION
Page 2-24
SEQUENCE OF OPERATIONS
REFRIGERATION SYSTEM
Model #: MCB(H)-1.2-.33-.33-H/AC and MCB(H)-3-.33-.33-H/AC
System 1 Description (Refrigerant R-404A) - Refer to drawing: MCB-RF00 and MC3(H)-RF00
The compressor (item 1) will pump compressed R-404A vapor through the discharge line. The discharge
refrigerant vapor enters the air-cooled condenser.
The air-cooled condenser (item 5) cools the high pressure R-404A vapor and condenses it into a high-
pressure liquid. The condenser fan motor will be energized anytime System 1 is running.
High-pressure liquid refrigerant exits the condenser. The liquid ! ows through a " lter-drier, sight glass, and into
the T.E.V. (item 11) where it changes to a low-pressure two-phase refrigerant. The two phase refrigerant is
cold due to the ! ashing of refrigerant. It enters the cascade condenser (item 13) where the heat from system
2 boils the rest of the R-404A into a vapor. The cascade condenser serves as the evaporator for system 1.
Superheated R-404A vapor exits the cascade condenser and moves through the system 1 suction line. to the
compressor.
System 2 Description (Refrigerant R-508B)
The compressor (item 41) will pump compressed R-508B vapor through the discharge line. The discharge
refrigerant vapor passes through the discharge desuperheating loop on the front of the condenser (item 44).
This cools the vapor before entering the cascade condenser.
The cascade condenser (item 13) cools the high pressure R-508B vapor and condenses it into a high-
pressure liquid.
High-pressure liquid refrigerant exits the cascade condenser. The liquid ! ows through a " lter-drier and enters
a tee. The tee will divert some of the liquid refrigerant to be used in the bypass circuit (see last paragraph of
this section). The rest of the refrigerant passes through the solenoid valve (item 49) then to 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
! ashing of refrigerant. It enters the evaporator where the refrigerant is distributed through the evaporator
coil. The evaporator (item 52) serves to boil the rest of the R-508B into a vapor. This boiling action cools the
chamber.
Superheated R-508B vapor exits the evaporator and moves through the system 2 suction line. A crank case
pressure regulator, (CPR) Item 28 (MC3 only) limits the suction pressure so the compressor does not over
load. A service port is located near the compressor.
The bypass circuit is composed of: The liquid injection solenoid valve (Item 60) and a capillary tube (Item 61).
The liquid injection valve will be energized when no cooling is required in the chamber. The vapor tank (item
55) is connected to a capillary tube (item 61a) then to the suction line.
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