7 - STANDARD CONTROL OPERATIONS AND OPTIONS
7.5 Control point
The control point represents the water temperature that the unit
must produce. The control point calculation is based on the active
setpoint and its reset.
control point = active se reset
7.5.1 Active setpoint
The control can manage two heating setpoints. The
first heating
setpoint
is normally used during occupied periods, whereas the
second heating setpoint
is used during unoccupied periods.
Depending on the current operating type, the active setpoint can
be selected:
•
By choosing the active setpoint in the General Parameters
menu (Setpoint Select, GENUNIT).
• Via the volt-free contacts (see section 3.7).
•
Via network commands [SP_SEL].
•
Via the schedule setting – schedule 2 (OCCPC02S).
See also section 5.9
Mode
Setpoint control
Local
Regardless of the current setpoint schedule, the user can select the
setpoint manually via the control interface (Setpoint Select, GENUNIT).
Remote
If the setpoint switch is used once, the setpoint schedule control
will be cancelled (setpoint control will be based on setpoint switch
selection only).
Network
Regardless of the current setpoint schedule, the user can select the
setpoint manually via the control interface (Setpoint Select, GENUNIT)
or the service tool. Once the forced selection is deactivated, the setpoint
schedule will be used again.
The following tables summarise the possible setpoint selections
based on the control type (local, remote, network) and the following
parameters:
•
Setpoint select.
•
Setpoint selection contact status.
•
Schedule 2 status for setpoint selection.
Local operating type
Setpoint Select
[SP_SEL]
Setpoint occupancy
[SP_OCC]
Active setpoint
1
sp 1
-
heating setpoint 1
2
sp 2
-
heating setpoint 2
0
auto
occupied
heating setpoint 1
0
auto
unoccupied
heating setpoint 2
Remote operating type
Remote Setpoint Switch [SETP_SW]
Active setpoint
open
heating setpoint 1
closed
heating setpoint 2
Network operating type
Setpoint Select
[SP_SEL]
Setpoint occupancy
[SP_OCC]
Active setpoint
0
auto
occupied
heating setpoint 1
0
auto
unoccupied
heating setpoint 2
7.5.2 Reset
Reset means that the active control point is modified so that
the machine capacity required is adjusted to be as close as
possible to the demand.
The reset source can be provided by one of the following:
• Outdoor air temperature that gives a measure of the load
trends for the building. When the outdoor air temperature
increases, the heating demand normally decreases and the
active setpoint will be decreased thanks to the applied reset.
• Return water temperature
(heat exchanger ΔT gives an
average building load). Delta T (ΔT) is the difference
between leaving and entering fluid temperatures (LWT minus
EWT). When the load is light, temperature difference across
the exchanger will be relatively small. The reset value should
be configured by the user and its configuration may differ
depending on the size of the water exchanger.
• 4-20 mA reset signal provided by an active sensor
connected to the input: If the reading of the 4-20 mA signal/
external temperature value increases (load is lighter), then
the current setpoint will be lowered.
In response to a change in the outside air temperature, Delta T,
or 4-20 mA reset signal reading, the control point is reset in order
to optimise unit performance. The source of the reset (OAT, ΔT,
4-20 mA signal) can be configured by the user.
To set the source of the reset
1. Navigate to the Configuration menu.
2. Select
Heat/Cool Config
(HCCONFIG).
3. Set
Heating Reset Select
[hr_sel].
Heating Reset Select [hr_sel]
0 = none
1 = OAT
2 = delta T
3 = 4-20mA
Reset is a linear interpolation function based on the following
three parameters:
• A reference at which reset is zero (no reset value).
•
A reference at which reset is maximum
(full reset value).
•
The maximum possible reset value:
The difference between
the lowest reset value (no reset value) and the highest
possible reset value (full reset value). “Heating Reset Deg.
Value” [hr_deg] represents the maximum possible reset.
Reset source
No reset parameter
Full reset parameter
OAT
oathr_no
oathr_fu
delta T (ΔT)
dt_hr_no
dt_hr_fu
4-20 mA signal
I_hr_no
I_hr_fu
-20°C
Reset based on OAT
+10°C
0 K
Reset based on delta T
3 K
4 mA
Reset based on analogue input
20 mA
no reset
selection
full reset
Legend:
A: Maximum reset value
B: OAT / delta T / 4-20 mA for no reset
C: OAT / delta T / 4-20 mA for full reset
D: Building load
Reset value [°C]
Building load [
%]
Reset example in Heating mode
AQUACIAT
CALEO
EN - 22
