Description of Functions and Operation
SiENBE28-901
48
Air Cooled Refrigeration Condensing Unit
4.3
Detailed Description of Functions
(1) Startup control
The actuators will be operated in the following sequence when the thermostat is
turned on:
1
The outdoor fan will start to operate for 5 seconds. (This is intended to measure the outdoor
temperature accurately.)
2
At power-up, the operation outputs (P1, P2) for low pressure conditions (see the chart on the
right) will be turned on/off.
(This is intended to avoid possible liquid compression that is caused by the thermostatic
expansion valve in the showcase being fully open during startup. To prevent liquid
compression, the liquid solenoid valve will be cycled on and off until the thermostatic
expansion valve catches up.)
3
The compressors will be activated.
(2) Thermostat ON/OFF
Thermostat off setting value
Lpm:
Lpm1 obtained after an outdoor temperature correction is made.
Lpm1: Pressure equivalent to the evaporation temperature set by the dip switches
(Tsd: Evaporation temperature set by the dip switches).
LP:
The pressure detected by the low pressure sensor (S1NPL)
Inverter compressor
Activation complete
Operation output
Fan
Operation prior to
compressor activation
Air flow rate corresponding
to the outdoor temperature.
This may be turned on in order to raise LP,
depending on outdoor temperature and the
thermostat OFF time.
LP>0.49MPa: Operation output OFF
LP<0.294MPa:Operation output ON
90sec
15sec
52Hz 15sec
56Hz
1
2
3
MT
LRMEQ**
LT
LRLEQ***
0.1MPa
-0.015MPa
Thermostat OFF
(Compressor stops.)
Thermostat ON
(Compressor starts.)
& or
&
&
• LP>Lpm1+0.15MPa
• Outdoor temperature Ta < Tsd
(the evaporation temperature set by the dip switches)
• 3 minutes after the thermostat is turned OFF.
• LP>Lpm1
• 3 minutes after the thermostat is turned OFF.
• The compressor standby mode before a restart is complete.
• Activation complete.
&
• LP < Thermostat off setting value
• LP < 0 MPa continuously for 5 seconds
or