SSB 6720892984 (2019/02) US
Main control | 31
5.2.1.4 CH mode 3 - CH with permanent heat demand
For this mode the
CH_Mode
should be set to 3, no outdoor sensor is
needed.
The supply temperature is kept constantly at the setpoint temperature.
The burner is controlled in a similar way as described in paragraph
“5.2.1.1 CH Mode 0 - Central Heating demand” pag. 26.
When the room thermostat contact opens
CH_Setpoint
will be
decreased with
Night_Setback_Temp
.
In this condition the pump is always ON.
NOTE: the pump start every 24 hours function is not performed during
this mode. The pump in this mode is continuously running.
Relevant variables
Parameters Level
(Default) Value Settable
°C °F °C °F
CH_Mode 2: Installer 0 0, 1, 2, 3, 4
CH_Setpoint 1: User 60 140 20..80 68..176
CH_Hysterese_Up 3: Factory 5 9 0..20 0..36
CH_Hysterese_Down 3: Factory 5 9 0..20 0..36
5.2.1.5 CH mode 4 - CH with Analog Input Control of setpoint
CH mode is set to 4. In this mode of operation, the boiler CH setpoint is
controlled by an analog input signal provided by a remote means such as
a building management system or a system controller. The analog input
0-10 Vdc, is used to adjust the boiler
setpoint between the
CH_Setpoint_Min
and the
CH_Setpoint_Max
settings.
The minimum analog input signal will correspond to the CH setpoint
minimum parameter and the maximum analog input signal will
correspond to the CH setpoint maximum parameter. All other safety and
control functions associated with the boiler will react normally to adverse
condition and override control of the analog signal to prevent an upset
condition.
The CH setpoint Min. and CH setpoint Max. parameters can be adjusted
to provide the desired temperature adjustment band. A heat request will
be generated by an input of 1.5 volts or higher. The setpoint modulation
will occur between 2 and 9 volts. The request for heat will be removed
when the voltage drops below 1 volt.
Fan Speed
Maximum
Fan Speed
Minimum
1.51.0 2.0 9
Voltage
OFF ONON/OFF
Hysterese
OFF
ON
Modulating
Relevant variables
Parameters Level
(Default) Value Settable
°C °F °C °F
CH_Mode 2: Installer 0 0, 1, 2, 3, 4
CH setpoint
Minimum
[°C/°F]
2: Installer 20 68 20..80 68..176
CH setpoint
Maximum
[°C/°F]
2: Installer 80 176 20..80 68..176
5.2.2 Demand for Domestic Hot Water (Rev 3.0.0.0)
5.2.2.1 DHW mode 0 – No Domestic Hot Water
No domestic hot water is available. The
T_DHW_Out
sensor does not
need to be connected.
5.2.2.2 DHW mode 1 – Storage with sensor
In DHW Mode 1 DHW is prepared by warming up a indirect tank. Either a
DHW pump or 3-way valve can used to switch to DHW mode.
The DHW temperature in the tank is measured with sensor
T_Store
and
set with parameter
DHW_Store_Setpoint
.
When this sensor drops below
DHW_Store_Setpoint
–
DHW_
Store_Hyst_Down
the control detects a demand for the store and
starts the general and DHW pump .
If the supply temperature
T_Supply
is below
DHW_Store_Setpoint
+
DHW_Store_Supply_Extra
–
DHW_Supp_Hyst_Down
the burner
is started as well.
When the burner is ON the power is PID-modulated so
T_Supply
is
regulated towards
DHW_Setpoint
+
DHW_Store_Supply_Extra
.
The burner is stopped when the supply temperature rises above
DHW_Store_Setpoint
+
DHW_Store_Supply_Extra
+
DHW_
Supp_Hyst_Up
.
The demand for the tank is ended when the tank-sensor rises above
DHW_Store_Setpoint
+
DHW_Store_Hyst_Up
.
The pump continues
DHW_Post_Pump_Period
.
DHW Priority
Standard DHW demand has priority over CH demand but the priority
period is limited up to
CH_DHW_Switching_Time
.
The priority timer starts when both CH and DHW demand are present.
After the
CH_DHW_Switching_Time
is achieved,
the control will switch from DHW to CH operation. CH has priority now for
a maximum period of
CH_DHW_Switching_Time
.
Different DHW Priority types can be chosen:
DHW priority Description
0 ¨ Time
DHW has priority to CH during
CH_DHW_
Switching_Time
1 ¨ Off
CH always has priority to DHW
2 ¨ On
DHW always has priority to CH
3 ¨ Parallel
DHW always has priority to CH.
CH Pump can be started if CH has a request and
CH_Setpoint
> Supply for DHW
Default DHW_Priority is set to 2.
Store warm hold function
Because of the presence of the store sensor (T_Store) the control can
detect demand for holding the store warm.
If
T_Store
drops below
DHW_Store_Setpoint
-
DHW_Store_
Hold_Warm
the burner starts at minimum power.
The burner stops if T_Store is higher than
DHW_Store_Setpoint
+
DHW_Store_Hyst_Up
.
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