69
12.7.2 CH
WITH AN OUTDOOR TEMPERATURE RESET AND
THERMOSTAT;
CH
MODE
1
If the parameter CH_Mode is set to 1, the “Outdoor temperature reset with room thermostat” mode is selected.
This mode will only function when an outdoor temperature sensor is connected. If the outdoor sensor is connected,
the boiler automatically uses Reset_Curve_Boiler_Maximum.
The setpoint is calculated depending on the outdoor temperature as indicated in the following graph and the boiler
will react on the room thermostat (as described in § 12.7.1).
CH outdoor reset curve
The outdoor reset curve can be changed by adjusting the design and mild weather reference temperatures. The
calculated CH-setpoint is always limited between parameters Reset_Curve_Boiler_Minimum and
Reset_Curve_Boiler_Maximum.
The outdoor temperature used for the CH_Setpoint calculation is measured once a minute and averaged with the
previous measurement. This is to avoid commuting when the outside temperature changes rapidly.
If an “open” outdoor sensor is detected the CH_Setpoint will be equal to the Reset_Curve_Design_Boiler.
Shutdown temperature
When the outdoor temperature rises above Warm_Weather_Shutdown, the call for heat is blocked and the pumps
are stopped. There is a fixed hysteresis of 1 °C (1.8 °F) around the Warm_Weather_Shutdown setting.
This means that the demand is stopped when the outdoor temperature has risen above Warm_Weather_Shutdown
1 °C (1.8 °F). When the outdoor temperature drops below Warm_Weather_Shutdown – 1 °C (1.8 °F) again, the
demand will also start again.
Boost function
The outdoor reset boost function increases the CH_Setpoint by a prescribed increment (Boost_Temperature_Incr)
if a call for heat continues beyond the pre-set time limit (Boost_Time_Delay).
Boiler Parameters
(25) Warm Weather Shutdn 22 °C ▲
(26) Boost Temp increment 18 °C
(27) Boost Time Delay 20 min
(28) Night Setback Temp. 4 °C ▼
These are parameters 26 Boost Temp Increment and 27 Boost Time Delay.
And have a default value of 18 °C (32 °F) and 20 min, so the function is switched off and can be activated by the
installer by increasing parameter 26 by a number of degrees. Also, the time can be set when this parameter will
be active in parameter 27 now set on 20 min.
CH_Setpoint increases again if the call for heat still is not satisfied in another time increment.
°
F
°
C
OUTDOOR TEMP.
Design
82 180
Boiler
71 160
°
C
°
F
93 200
Outdoor Design
Outdoor Mild Weather
Boiler Maximum
60 140
16 60
Boiler Minimum
Warm Weather Shutdown
CH SETPOINT
OFF
Boiler
Mild
Weather
49 120
38 100
27 80
40
4
20
-6 4
60
16
80
27
100
38
Summary of Contents for S-CBX 105
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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 ...
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