Specifications are subject to alteration without notice.
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1.2.2 Size 24, 34, 48 and 60 Coolers
BT2 RP2:2
BT1 RP1:2
SV EK
SV EK
M2
M1
RP2:1
RP1:1
G1
BT3
BT4
VVX1
VVX2
VVX3
VVX4
EV2
EV1
G2
HT
SS
Cooling coil
Cooling agent
cooler
E1
Fig. 4
BT1
Hot gas thermostat R134A
BT
Hot gas thermostat R407C
BT3
Brine temperature
BT4
Cooling agent temperature
RP1:
High pressure switch R134A
RP:
High pressure switch R407C
RP1:1
Low pressure switch R134A
RP:1
Low pressure switch R407C
G1
Brine pump
G
Heating medium pump
M1
Compressor R134A
M
Compressor R407C
VVX1
Condenser
VVX
Condenser
VVX3
Evaporator
VVX4
Evaporator
EK
Expansion vessel
SV
Safety valve
E1
Ellectrical cubicle with safety switch, power sec-
tion, control card
SS
Start and control signal
EV1
Expansion valve 1
EV
Expansion valve
HT
Hand-held micro terminal
operation
There are two refrigerant circuits in the cooling unit. The
circuits are separate from one another and each contains a
different type of refrigerant.
Each circuit is equipped with its own set of heat exchang-
ers on the warm and cold side respectively. The cooling
agent and the brine (water/ethylene glycol) both pass
through the heat exchanger of both refrigerant circuits.
The refrigerant in gas form is compressed by each com-
pressor and then advances to condenser VVX1 or VVX,
where it is chilled by the cooling agent (water/ethylene
glycol) and condenses to liquid form.
A reduction in pressure occurs in expansion valve EV and
the pressure drops. From the expansion valve the refrig-
erant advances to evaporator VVX3 or VVX4 where the
refrigerant vaporises, boils, and absorbs heat from the
adjacent medium, i.e. the brine (water/ethylene glycol).
Gas leaves the evaporator and flows back to the cooling
compressor.
Water pump G1 pumps the brine (water/ethylene glycol)
in one circuit from condensers VVX3 and VVX4 where the
brine is chilled by the refrigerant and then proceeds to
the cooling coil, where it in turn cools the supply air dis-
charged from the air handling unit.
Water pump G pumps brine (water and ethylene glycol)
in the circuit from condensers VVX1 and VVX, where the
brine cools the refrigerant and further to the brine cooler
(the coil in the exhaust air duct). The brine is cooled there
where it transfers heat to the exhaust air leaving the air
handling unit. After that the brine returns to the conden-
ser.
If the cooling agent isn’t chilled adequately, the COOLER
will temporarily lower its capacity to avoid a shutdown
(shuts off one refrigerant circuit and compressor). The
cooling unit will however revert to operating at full capa-
city again as soon as the operating conditions so permit.
Control
In response to an ON/OFF control signal, the controller
switches in pumps G1 and G and compressor M1. The
cooling capacity is controlled by switching in one or both
compressors. On increasing cooling load the controller
switches in compressor M and at the same time
switches out compressor M1. If still more cooling is re-
quired compressor M1 is switched in to operate together
with M.
If the temperature of the outgoing brine becomes too
low, one of the compressors is switched out. When the
condition subsides, it is restarted automatically. Should the
pressure become too low, the low pressure switch will trip.
The equivalent will occur on the warm side. If the tem-
perature of the exhaust air becomes too high, one of the
compressors is switched out. If the pressure still rises, the
high pressure switch will trip.
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