McQuay SEASONCON ALP-037A, Руководство пользователя, Страница: 39 / 43

HIGH PRESSURE CONTROL
The high pressure control is a single pole pressure activated by watching condenser pressure rise. The highest point
switch that opens on a pressure rise to de-energize the reached before cut-out is the cut-out setting of the control.
entire control circuit except for compressor crankcase
heaters. It senses condenser pressure and is factory set to
open at 380 PSIG and can be manually reset closed at 315
PSIG. To check the control, either block off condenser
surface or start the unit with fuses in only one fan fuse
block (FBI 1) and observe the cut-out point of the control
CAUTION:
Although there is an additional pressure relief
device in the system set at 450 PSIG, it is
highly recommended that the
stop“
switch be close at hand in case the high
pressure con trol should malfunction.
LOW PRESSURE CONTROL
The low pressure control is a single pole pressure switch
that closes on a pressure rise. It senses evaporator pressure
and is factory set to close at 60 PSIG and automatically
open at 25 PSIG. The control has an adjustable range of 20
inches of Hg. to 100 PSIG and an adjustable differential of
6 to 40 PSIG. To check the control (unit must be running),
move the pumpdown switch(es) PSI and PS2 to the “man-
ual pumpdown” position. As the compressor pumps down, condenser pressure will rise and evaporator pressure will
drop. The lowest evaporator pressure reached before cut-
out is the cutout setting of the control. By moving the
pumpdown switch(es) PSI and PS2 to the “auto. pump-
down” position, evaporator pressure will rise. The highest
evaporator pressure reached before compressor re-start is
the cut-in setting of the control.
FANTROL -HEAD PRESSURE CONTROL
FANTROL is a method of head pressure control which
automatically cycles the condenser fans in response to con-
denser pressure and ambient air temperature. This main-
tains head pressure and allows the unit to run at low
and 14, circuit 1, and 23 and 24, circuit 2, are controlled
by ambient temperature and are factory set at the values
given in Table 13. Note that the number of fans on each
unit varies.
ambient air temperatures.
For ALP-037A thru 078B:
Models ALP-046A thru 078B have dual independent cir-
cuits with the fans for circuit 1 (11, 12, 13, 14) and circuit
2 (21, 22, 23, 24) being controlled independently by the
condensing pressure and ambient air of each circuit. Fans
11 and 21 start with each compressor and fans 12 and 22
cycle on and off in response to condenser pressure. The
cut-out and cut-in pressures are given in Table 13. Fans 13
TABLE 13. FACTORY FANTROL SETTINGS
For ALP-089B thru 159B:
The first fan (1 1) is started when the first compressor in the
unit starts. Fan 12 is controlled by parallel wired pressure
switches which sense condenser pressure in circuit 1 and 2.
The third fan (13) is controlled by parallel wired tempera-
ture switches, one of which senses condenser inlet air for
circuit 1 and the other senses condenser inlet air for circuit
2. Refer to Table 13 for cut-out and cut-in settings of these
controls.
ALP-067B 270 PSI 170 PSI 270 PSI 170 PSI 74F 69F 7 4 F 6 9 F 6 9 F 6 4 F 6 9 F 64F
A L P - 0 7 8 6 280 PSI 170 PSI 280 PSI 170 PSI 74F 6 9 F 74F 6 9 F 6 6 F 61F 66F 61 F
ALP-089B
T H R U
2 7 0 170
_
8 0 F t
_
_ _
ALP-159B
PC2 and TC6
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