SSB 6720866940 (2017/11) US
Parameters description | 17
6 Parameters description
6.1 Central Heating (CH)
Par.1 CH_Mode
CH_Mode=0 Request for Heat from Room Thermostat or a zone relay
end-switch.
If the room thermostat closes, the “Main” and “CH” pump contacts on
the boiler are energized. If the supply temperature drops CH_Hysterese
(boiler settings parameter #7) below the CH_Setpoint the burner is
switched ON. If the room thermostat opens, the burner is switched OFF
and the CH and general pumps run ON for a time equal to CH_Post_
Pump_Period (boiler settings prameter #4 and #5).
Anti-cycling time
(Also applicable to all other CH Modes) When the burner is switched OFF
because the supply temperature reaches CH_Setpoint + CH_Hysterese,
the control will wait a period of time, Anti_Cycle_Period (180 sec.
settable), before it is allowed to be switched ON again. This function is to
prevent short cycling of the burner.
However when during the anti-cycle wait time the differential between
setpoint and supply temperature may become greater than Anti_
Cycle_T_Diff, anti-cycle will be aborted and the burner is allowed to start.
Maximum CH power
(Also applicable to all other CH Modes)
The maximum burner power during CH operation can be limited with
parameter P_CH_Max.
Minimum CH and DHW power
(Also applicable to all other CH and DHW Modes)
The minimum burner power during operation can be limited with
parameter P_Min.
CH_Mode=1 Request for Heat with Outdoor Sensor and Room
thermostat.
If the parameter CH_Mode is set to 1 “Outdoor temperature reset with
room thermostat” mode is selected. This mode will only function when
an outdoor temperature sensor is connected, but default setting can
be customer specic for production series. If the outdoor sensor is
connected the boiler automatically uses the Max Supply Temp.
The setpoint is calculated depending on the outdoor temperature as
indicated in the graph below (“Fig. 42”) and the burner will react on the
room thermostat. The outdoor reset curve can be changed by adjusting
the design and mild weather reference temperatures.
The outdoor temperature used for the CH_Setpoint calculation is
measured once a minute and averaged with the previous measurement.
This is done to avoid commuting when the outside temperature changes
quickly. If an “open” outdoor sensor is detected the CH_Setpoint will be
equal to the Design Supply Temp.
Par.19: Design Supply Temp.
Sets the maximum supply temperature when the outdoor temperature is
equal to Par. 20 “Design Outdoor Temp.”.
Par.20: Design Outdoor Temp.
Represents the minimum outside temperature setable to calculate the
maximum set point of CH.
Par.21: Baseline Supply Temp.
Represents the minimum settable supply temperature targeted when the
outdoor temperature exceeds parameter 22. “Baseline Outdoor Temp”.
20
CH SETPOINT (°C/ )°F
OUTDOOR TEMP. (°C/ )°F
Par. 19 Design
Supply Temp.
93
Par.20 Design Outdoor Temp.
1)Par.22 Baseline Outdoor Temp.
2) Par.25 Warm Wheather Shutdown
Par. 21 Baseline
Supply Temp.
Par. 24 Max Supply Temp.
200
82 180
71 160
60 140
12049
10038
27 80
60
16
°C °F
-6
40
4
60
16
80
27
100
38
°F
°C
Par. 23 Min. Supply Temp.
Fig. 42
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