GENERAL DESCRIPTION
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Mode: Pumpdown (10 HP - 15 HP systems)
When the conditioning system is turned off, the refrigeration system will go into pumpdown mode. In
pumpdown mode, the compressor will automatically turn on when the pressure in the suction line is
above 50 PSIG (3.4 bar(g)). The compressor turns off when the suction line pressure is reduced to 5 PSIG
(0.3 bar(g)). Pressure switch (107-PS) will monitor the suction line pressure and control the operation of
the compressor in pumpdown mode. The maximum liquid line solenoid (101-SOL), the minimum liquid
line solenoid (107-SOL), and the hot gas bypass solenoid (109-SOL) will be deenergized. Pumpdown
forces most of the refrigerant into the high side of the system. The refrigerant will be in the liquid line,
filter-drier, sight glass, receiver, condenser, and discharge line. Pumpdown serves to protect the
compressor on startup. If there was no pumpdown, a slug of liquid refrigerant could exit the evaporator
coil and damage the compressor.
SINGLE STAGE - SYSTEM 1 (R-404A) DESCRIPTION
Refer to Refrigeration Diagram in Drawing Section.
The compressor (item 101) will pump compressed R-404A vapor through the discharge line where the
high pressure gauge (item 183) displays the pressure of the refrigerant. The high pressure switch (item
195) 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.
Air Cooled Condensing Option
The condenser (item 105) cools the high pressure R-404A vapor and condenses it into a high pressure
liquid. The condenser fan motor (item 196) will be energized anytime the compressor (item 101) is
running.
The high pressure liquid leaves the condenser and flows through a filter drier (item 108) and sight
glass (item 109), then passes a tee which diverts some of the liquid refrigerant to the bypass loop (see
bypass description).
Water Cooled Condensing Option
The condenser (item 105) cools the high pressure R-404A vapor and condenses it into a high pressure
liquid. The pressure actuated water valve (item 107) will maintain the discharge pressure at
approximately 210 PSIG (14.5 bar(g)).
The high pressure liquid leaves the condenser and flows through a receiver (item 122), filter drier (item
108), and sight glass (item 109), then passes a tee which diverts some of the liquid refrigerant to the
bypass loop (see bypass description).
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