OPERATING INSTRUCTIONS
CO
2
/NH
3
CASCADE UNIT
250 - 1000 KW
_551511_om_kas_gbr_1_.doc 21
— “Switch on pause" timer starts up
1.6.2.17 Automatic mode
6. If the NH
The system is designed for automatic chilling; it is
controlled by the compressor being switched on and
off and its output adjustment.
3
compressor is in minimum output and
the value falls further below the setpoint value
the compressor switches off.
Continuous operation and observation of the
machine is not necessary in automatic mode. The
necessary information on starting up the system is
given in the documentation for the compressor
control.
1.7 Shutdown in the event of dangerous
situations
The safety equipment of the CO
2
/NH
3
cascade
conforms to EN378 and UVV BGV4.
Danger!
Due to the automatic monitoring of the individual
operating parameters, the control detects hazardous
situations in good time and automatically switches
off the cascade.
Do not carry out any work on the
cascade during an "Automatic
shutdown"!
The cause of the fault is then displayed on the
control unit and can then be corrected.
Special features of automatic mode
The cascade concept is based, among other things,
on the most tight, low-maintenance refrigerant
circuits possible. However, residual risks remain,
especially due to possible leaks or escaping
refrigerant or rotating drive parts.
1. Fulfilment of the following requirements:
— Release signal issued by GSC
— Switching on conditions for the compressor
drive motors are fulfilled
Hint!
— There are no queued faults
The cascade can be switched off at any
time via the EMERGENCY STOP button
on the switch cabinet.
— System signals output requirements
(temperature setpoint is smaller than actual
value)
2. NH
3
compressor drive motor starts up
The auxiliary refrigeration unit has its own supply
and can be taken out of service via a separate
EMERGENCY STOP button.
— Oil heater is switched off
— "EHB" (starting frequency limiter) timer starts
up
When the cascade is switched off, taking the
auxiliary unit out of pressure can result in a pressure
increase in the CO
3. If the switching on conditions for the CO
2
compressor drive motor are fulfilled the motor
starts up.
2
cycle and can cause the discharge
safety valve in the CO
circuit to trigger.
2
Leaking refrigerant in the machine room can be
detected with the help of a gas detector and alarm
(not included in scope of supply) and can be
integrated in the automatic safety chain.
— Oil heater is switched off
— "EHB" (starting frequency limiter) timer starts
up
4. The control variable for automatic operation of
the cascade is the suction pressure of the CO
Hint!
2
circuit. The difference between this actual value
and the specified setpoint causes the automatic
switching on and off of the CO
The safety information for the NH
3
and
CO
refrigerants must be observed!
2
2
and NH
3
compressor output levels.
5. At minimum output and if the pressure
continues to drop below the set "setpoint
pressure" the cascade switches off.
At minimum output and if the pressure
continues to drop below the set "setpoint
pressure" the CO
unit switches off.
2
— CO
compressor drive motor is switched off
2
— Oil heater is switched on
To Next Page
Loading...
