Alpha E-Tec Plus 28NX - Page 31

Alpha E-Tec Plus 28NX, 33NX and 38NX - Installation
External Sensor – Weather compensation feature
The E-Tec Plus NX boilers have a built in weather compensation feature which is automatically activated when
the external sensor is fitted – Part No 3.022383. When fitted the weather compensation sensor allows the boiler to
control the maximum primary flow temperature to the heating circuit according to the outside temperature, heating
the property more effectively and efficiently.
Operation
During a central heating on period the sensor monitors the external temperature and modulates the boiler heating output to
give the correct flow temperature to maintain the required room temperature. If the external temperature drops then the flow
temperature will increase, if the external temperature increases then the flow temperature will decrease. This reduces the
amount of wasted energy and reduces gas consumption.
When an external weather sensor is fitted the CH temperature control buttons will no longer adjust the flow temperature in
°C, instead the display will show a scale of 1 to 9. Each number corresponds to a line on the graph in Fig. 5.22 e.g. line 6 will
give a flow temperature of 60°C when the external temperature is 10°C.
Note: The temperature of the radiators will vary depending on the outside temperature; the required room temperature will
still be maintained by the room thermostat.
Fig. 5.22
98
7
6
5
4
3
2
1
27 20 15 10
5
0
-5
-10 -15 -20
External temperature (°C)
Max.
Min.
System
temperature
(°C)
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