Capacity Control; Dry Cooler Free Cooling (Dcfc); Night Mode - Carrier SmartVu control Manual

6 - STANDARD CONTROL OPERATIONS AND OPTIONS

6.10 - Capacity control

The control adjusts the capacity to keep the water exchanger
temperature at its setpoint. Compressors are started and stopped
in a sequence designed to equalise the number of starts (value
weighted by their operating time).
6.10.1 - Circuit loading sequence
This function determines in which order the circuit capacity is
changed. Compressor loading is managed by starting/stopping
the compressors. Two types of sequencing, i.e. balanced and
staged loading sequence, are available and can be configured by
the user via the user interface (GENCONF – General Config).
■ Balanced loading sequence: The control maintains equal
capacity between all circuits as the machine loads and unloads.
Balanced loading sequence is the default sequence employed
by the control.
■ Staged loading sequence: The control loads the lead circuit
completely before the lag circuits are started. When the load
is decreasing, the lag circuit is unloaded first. Staged loading
sequence is active when one of the circuits is shut down due
to its failure; the circuit is in capacity override mode; or the
remaining circuits are shut down or fully charged.
To set the circuit loading sequence
1. Navigate to the Configuration menu.
2. Select General Config (GENCONF).
3. Set Staged Loading Sequence [seq_typ].
Staged loading sequence [seq_typ]
No/Yes No
6.10.2 - Capacity for multi-circuit unit
The circuit lead/lag function determines the lead and lag circuit of
the unit. This function controls the start/stop sequence of two
refrigeration circuits called circuit A and circuit B.
The circuit authorised to start first is the lead circuit. Lead circuit
is used first for capacity increases and at the same time should
be decreased first when decreasing capacity. The lead/lag circuits
can be selected manually or automatically (Cir Priority Sequence,
GENCONF – General Config).
■ Manual lead/lag circuit determination: Circuit A or circuit B
selected as the lead circuit. The selected circuit takes priority
over another circuit.
■ Automatic lead/lag circuit determination: The control system
determines the lead circuit to equalise the operating time of
each circuit (value weighted by the number of start-ups of each
circuit). As a result, the circuit with the lowest number of
operating hours always starts first.
To set circuit priority
1. Navigate to the Configuration menu.
2. Select General Config (GENCONF).
3. Set Cir Priority Sequence [lead_cir].
Cir Priority Sequence [lead_cir]
0 Auto
1 A Lead
2 B Lead
40

6.11 - Dry Cooler Free Cooling (DCFC)

30RBS chillers may be fitted with a dry cooler that enables power
consumption reduction which amounts to energy and cost savings
(DC FREE COOLING).
The installation of a dry cooler allows for "free cooling", i.e. a method
of using low outdoor air temperature as an aid to chilling water that
is later used in the air-conditioning system. The system is the most
effective when the outdoor air temperature is below 0°C (32°F).
This "dry cooler free cooling" mode is enabled when the outside
air temperature ("OAT Free Cooling") is below the water loop
temperature and the service-configured threshold parameter.
NOTE: Dry cooler water loop temperature and free cooling
OAT measured by the control are read-only values that can
be verified in the DC Free Cooling Status menu (DCFC_STA).
The control distinguishes between two types of fan control for
a dry cooler free cooling option, where the first one embraces the
use of fan staging and the second one that includes the use of
variable speed fan. Mixed configuration can also be used (fixed
and variable-speed fan control at the same time).
Dry cooler free cooling is normally stopped when the outside air
temperature ("OAT Free Cooling") is above the water loop
temperature and the service-configured threshold parameter.
However, if it turns out that the cooling power of the dry cooler is
not enough in order to reach the cooling setpoint, then the
mechanical cooling will be started (when FC capacity is at 100%,
then mechanical cooling can be started).
To verify water loop temperature
1. Navigate to the Main menu.
2. Select DC Free Cooling Status (DCFC_STA).
3. Verify FC Water Loop Temp [wloop].
FC Water Loop Temp [wloop]
°C/°F
To verify outdoor air temperature
1. Navigate to the Main menu.
2. Select DC Free Cooling Status (DCFC_STA).
3. Verify OAT Free Cooling [oat].
OAT Free Cooling [oat]
°C/°F
NOTE: OAT can also be read from the Synoptic screen.

6.12 - Night mode

Night mode allows users to configure the unit to operate with
specific parameters in a specific time period. During the night
period, the unit capacity is limited. The number of operating fans
is reduced (in cooling mode only).
The night period is defined by a start time and an end time that
are the same for each day of the week. The Night mode settings
or the maximum capacity value can be configured via the
Configuration menu (GENCONF – General Config). Only logged-
in users can modify the night mode settings.
To set the night mode
1. Navigate to the Configuration menu (logged-in users only).
2. Select General Config (GENCONF).
3. Set parameters corresponding to the night mode.
Night Mode Start Hour [nh_start]
00:00 to 24:00
Night Mode End Hour [nh_end]
00:00 to 24:00
Night Capacity Limit [nh_limit]
0 to 100% 100%