31
8.12 - Coil pressure control
The coil pressure of each circuit is managed by a maximum
of two fans in circuit A and one fan in circuit B.
30RBS/30RQS units are fitted with fixed speed fans or
variable speed fans which provide higher part load
efficiency and reduced acoustic levels
.
In cooling mode, the condensing pressure is controlled
independently in each circuit based on the saturated
condensing temperature. The control permanently adjusts
its setpoint to guarantee optimal performance and ensure
anti-short-cycle protection of the fans.
In heating mode, the evaporating pressure is controlled
independently on each circuit based on the saturated
suction temperature. The control permanently adjusts its
setpoint to guarantee optimal performance, delay and limit
frost accumulation on coils.
8.13 - Holidays
This function is used to define 16 holiday periods. Each
period is defined by three parameters,
i.e. the month, the
start day and the duration of the holiday period.
During the holiday periods the controller will be in
occupied or unoccupied mode, depending on the periods
validated as holidays. Each holiday period can be modified
by the user via the Configuration menu (HOLIDAY –
Holiday Menu).
To modify holiday periods
1. Navigate to the Configuration menu.
2. Select
Holiday Menu
(HOLIDAY).
3. Choose the holiday period, e.g. HOLDY_01.
4. Set
Holiday Start Month
[HOL_MON],
Start Day
[HOL_DAY],
Duration (days)
[HOL_LEN].
Holiday Start Month [HOL_MON]
0-12
0
Start Day [HOL_DAY]
0-31
0
Duration (days) [HOL_LEN]
0-99
0
8.14 - BACnet option
The BACnet/IP communication protocol is used by BMS
or the programmable controllers to communicate with the
control.
IMPORTANT: BACnet option can be installed only by
Carrier service.
8.15 - Desuperheater option
30RBS/30RQS
units may be fitted with a desuperheater
that allows for better energy management.
The desuperheater is used to extract the high pressure,
high temperature heat from the refrigerant to
“desuperheat” it to a lower pressure refrigerant. The
vapour that goes into the desuperheater is not fully
condensed; therefore, the refrigerant vapour must be
channelled to a separate heat exchanger where the
condensing process occurs.
To set minimal condensing setpoint
1. Navigate to the Main menu.
2. Select
Setpoint
(SETPOINT).
3. Set
Desuperheat Min SCT
[min_sct].
Desuperheat Min SCT [min_sct]
26.7 to 60.0°C
40.0°C
80.0 to 140.0°F
104.0°F
8.16 - Defrost cycle for heat pumps
When the outside air temperature is low and the ambient
humidity is high, the probability of frost forming on the
surface of the outdoor coil increases. The frost covering the
outdoor coil may decrease the air flow across the coil and
lead to lower performance of the unit. To remove the frost
from the coil, the control initiates the defrost cycle when
necessary.
During the defrost cycle, the circuit is forced into the
cooling mode. To prevent the water loop from cooling
down, optional electric heating may be started. The defrost
cycle lasts until the end of defrost temperature is achieved.
8.17 - Master/Slave assembly
The control system allows for master/slave control of two
units linked by the CCN network. The master unit can be
controlled locally, remotely or by network commands
(CCN), while the slave unit remains in Network mode.
All control commands to the master/slave assembly
(start/stop, setpoint selection, heating/cooling, etc.) are
handled by the unit which is configured as the master. The
commands are transmitted automatically to the slave unit.
If the master chiller is turned off while the master/slave
function is active, then the slave chiller will be stopped.
Under certain circumstances, the slave unit may be started
first to ensure that the run times of the two units are
equalised.
In the event of a communication failure between the two
units, each unit will return to an autonomous operating
mode until the fault is cleared. If the master unit is stopped
due to an alarm, the slave unit is authorised to start.
IMPORTANT: Master/slave assembly can be configured
only by Carrier service.
