Capacity Limitation - Carrier SmartVu control Manual

6 - STANDARD CONTROL OPERATIONS AND OPTIONS
6.8.2 - Reset
Reset means the active setpoint is modified so that less machine
capacity is required. In the cooling mode the setpoint is increased,
whereas in the heating mode it is decreased.
The reset can be based on the following possibilities:
■ OAT that gives the measure of the load trends for the building.
■ Return water temperature (ΔT provides the average building
load).
■ Dedicated 4-20 mA input.
The reset source and the reset parameters can be configured in
the Main menu (RESETCFG – Reset Config). In response to a
change in the reset source (e.g. OAT), the setpoint is normally
reset to optimise unit performance.
The amount of reset is determined by linear interpolation
based on the following parameters:
■ A reference at which reset is zero (no reset value).
■ A reference at which reset is maximum (full reset value).
■ The maximum reset value.
Reset example in Cooling mode for the space temperature:
20 Reset based on OAT
0 Reset based on delta T
4 Reset based on analog input
no_reset
Legend
A: Maximum reset value
B: Reference for zero reset
C: Reference for maximum reset
D: Building load
To select the type of reset
1. Navigate to the Configuration menu.
2. Select Heat/Cool Config (HCCONFIG).
3. Set Cooling Reset Select [cr_sel]
or Heating Reset Select [hr_sel].
Cooling Reset Select [cr_sel] / Heating Reset Select [hr_sel]
0 None
1 OAT
2 DeltaT
3 4-20 mA
Selection full_reset

6.9 - Capacity limitation

The control system allows for the constant control of the unit
capacity by setting its maximum allowable capacity.
Capacity limitation is expressed in percentage, where a limit value
of 100% means that the unit may run with its full capacity (no
limitation is implemented).
The unit capacity can be limited:
■ By means of user-controlled volt-free contacts. The unit capacity
can never exceed the limit setpoint activated by these contacts.
Contact
LIM_SW1
LIM_SW2
■ By demand limit [DEM_LIM] set via the communication protocol
(System Manager or the Master unit in the Master/Slave
assembly control).
■ By night mode limitation control. If the night mode is active and
the night capacity limitation is lower than the limitation due to
contacts, then the night capacity limit will be used.
To set limit setpoints
1. Navigate to the Main menu.
2. Select Setpoint (SETPOINT).
3. Set Switch Limit Setpoint 1 / 2 / 3 [lim_sp1 / 2 / 3].
Switch Limit Setpoint 1 / 2 / 3 [lim_sp1 / 2 / 3]
0 to 100% 100%
To verify the active demand limit
1. Navigate to the Main menu.
2. Select General Parameters (GENUNIT).
3. Verify Active Demand Limit Val [DEM_LIM].
25
Active Demand Limit Val [DEM_LIM]
3
0 to 100% 100%
20
Based on the limit source, the active demand limit value (DEM_LIM)
is set to the lowest possible value. Active Demand Limit Val
[DEM_LIM] can be forced by Network.
To set the night mode limit
1. Navigate to the Configuration menu.
2. Select General Config (GENCONF).
3. Set Night Capacity Limit [nh_limit].
Night Capacity Limit [nh_limit]
0 to 100% 100%
Switch Limit Setpoint
None (100%) Limit 1
Open Close
Open Open
Limit 2 Limit 3
Open Close
Close Close
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