1-16
1.4.6 Common Control
●Compressor running control
Compressor changes speed Min.1200 r/min to
Max. 7800 r/min with inverter control.
＊ Compressor's revolution will be displayed "rps" in
screen.
①
Start up control
③
Pull down control
⑤
Modulated control
Compressor
Time
Max.
7800 r/min
Min.
1200 r/min
②
Step up control
④
Step down control
Cooling OFF
SP
RS or SS
Unit ON
Approx.
4000 r/min
①Start up control
After unit switch ON, unit goes to modulation valve
Initial opening control first and compressor start up
control. Start up control is to protect compressor
from heavy wet compression when unit stops
for long time under low ambient temperature. It
is controlled with three steps: (1) pump down
operation, (2) operation not in wet conditions 1,
(3) operation not in wet conditions 2. Although it
normally completes in several minutes, sometimes
it takes almost 20 minutes if totalizing the time of
guard timer at each step. The compressor runs at
medium rotating speed (3800〜5700r/min).
②Step up control
After completion of start-up control, the rotation speed will
increase to the maximum speed of the pull down operation
by having a few steps. It takes approximately two minutes.
③Pull-down control
It runs at the maximum rotating speed (7800 r/min)
during pull down. When some cause makes the
protection control activated, the rotating speed may
decrease, giving a high priority on the protection control.
④Step down control
When the control temperature RS (frozen) or SS
(chilled) reaches the setpoint temperature SP, the
rotating speed of the compressor will be slowed
down gradually. It takes two to three minutes.
⑤Modulated control
When the control temperature RS or SS reaches SP, the
modulated control starts, and the compressor controls
rotation speed in response to temperature difference
between RS (or SS) and SP. (at the speed of as low as
1200 r/min)
The compressor stops when the load becomes light.
●Modulation valve initial operation
Turning the unit switch into ON triggers initial operation
of the modulation valves EEV, EMV, and DMV.
EEV and EMV are fully opened (420pls) then fully
closed (0pls). DMV is fully opened (760pls), then
fully closed (0pls) and fully opened (760pls) again.
The change of valve opening can be checked on
the LCD screen. Operate keys immediately when
the operation screen is displayed. It can be used
for the function check of modulation valve coils
when in service. (Refer to ※3 Sensor information in
paragraph 2.3.)
●Compressor protection control
When an operating status phenomenon is
detected, rotation speed of the compressor will
gradually slow down to protect the compressor. It
will resume to normal operation when the operation
status returns to normal. Three examples follow.
1. Suppression control of high-pressure increase
starts at HPT≧2110kPa.
2. Suppression control of low-pressure decrease
starts at LPT≦-50kPa.
3. Suppression control of discharged-gas-
temperature increase starts at DCHS ≧117℃ .
●High pressure control
When ambient temperature is low, the high
pressure will decrease. Accordingly, the low
pressure will decrease too. In order to prevent
this situation, optimum pressure is maintained by
switching the condenser fan between OFF⇔Low
speed⇔High speed based on the high pressure
value.
High Speed
Low Speed
OFF
HPT<800kPa
HPT>800kPa
HPT>1000kPa
HPT<600kPa
＜
In operation
＞
＜Startup＞
High Speed
Low Speed
OFF
HPT<500kPa
HPT>400kPa
HPT>600kPa
HPT<300kPa
Pressure
Pressure
SpeedSpeed
＊ The control values described above may vary
depending on operation status.
＊ CFM stops for ten seconds when switching from
high speed to low speed.
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