75
12.8.3 DHW
S
TORAGE WITH THERMOSTAT
;
DHW
MODE
2
In this mode DHW is prepared by warming up an indirect tank. Either a DHW pump or 3-way valve can be used
to switch to DHW mode. The temperature of the DHW in the indirect tank is regulated by a thermostat (instead of
a sensor), which should provide only an open/closed signal to the control.
When the thermostat closes the control detects a demand from the DHW indirect tank and starts the DHW pump.
If the supply temperature T_Supply drops below DHW_Store_Setpoint – DHW_Supp_Hyst_Down the boiler starts.
When the boiler is ON the power is PID-controlled based on T_Supply toward DHW_Store_Setpoint.
The boiler is stopped when the supply temperature rises above DHW_Store_Se DHW_Supp_Hyst_Up.
The demand for DHW ends when the indirect tank thermostat opens. The pump continues
DHW_Post_Pump_Period after the DHW demand has stopped.
DHW priority
See chapter 12.8.2 – DHW Mode 1 – Storage with sensor
Relevant variables
Specific Parameters
Level
(Default) Value
Range
DHW_Mode
2: Installer
0
0, 1, 2,3, 4, 5, 6, 7, 8
DHW_Store_Setpoint
Sets the supply temperature from the boiler to
prepare DHW in the indirect tank
2: User
57 ºC (135 ºF)
40…85 ºC
(104…185 ºF)
DHW_Priority
[-]
2
0=Time, 1=OFF, 2=ON
DHW_Max_Priority_Time
Sets the maximum time for either DHW or CH priority.
2: Installer
60 min.
DHW_Post_Pump_Period
2: Installer
120 sec.
10...900
12.8.4 I
NSTANTANEOUS WATER HEATING WITH PLATED HEAT EXCHANGER
;
DHW
MODE
3
In DHW mode 3 the water flow through a plated heat exchanger is checked with a flow switch. If the switch
closes a water flow is detected, and either a DHW pump or a 3-way valve can be used to switch to DHW mode.
The temperature of the DHW is set with
DHW_Setpoint
.
If the
T_DHW_Out
sensor drops below
DHW_Setpoint
–
DHW_Hyst_Down
the burner starts. When the burner is
on, the power is PID-controlled based on
T_DHW_Out
toward
DHW_Setpoint
. The burner stops when the
T_DHW_Out
temperature rises above
DHW_Setpoint
+
DHW_Hyst_Up
. When the flow switch opens the
demand for the tapping is ended and the burner stops. The pump continues
DHW_Post_Pump_Period.
Based on a DHW temperature rise of 50 °C (90 °F) following minimum and maximum DHW flows are advised:
Boiler model
Minimum flow (litre/ min) Maximum flow (litre/ min)
S-CBX 85
4.4
23.5
S-CBX 105
5.3
27.9
S-CBX 125
6.8
34.3
S-CBX 155
10.0
41.7
Specific Parameters
Level
(Default) Value
Range
DHW_Mode
2: Installer
0
0, 1, 2,3, 4, 5, 6, 7, 8
DHW_Setpoint
Sets the desired DHW temperature
2: User
50 ºC (122 ºF)
30…80 ºC
(86…176 ºF)
DHW_Post_Pump_Period
2: Installer
20 s
10…900 s
Summary of Contents for S-CBX 105
Page 2: ......
Page 40: ...40 9 10 Flue Terminal Positioning ...
Page 42: ...42 9 11 1 FIGURE 12 LINE G ...
Page 55: ...55 11 5 Ladder Logic Diagram ...
Page 56: ...56 11 6 Electrical schematics ...
Page 57: ...57 ...
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