3
Alpha InTec² 25XE and 28XE
Summer setting - This function can only be used for hot water operation if the boiler is fitted with an Alpha Diverter
kit or Relay kit. With the Alpha Diverter kit fitted the DHW control knob on the boiler will independently control the
temperature of the hot water cylinder. With the DHW relay kit fitted the DHW control knob on the boiler sets the
water temperature leaving the boiler to heat the hot water cylinder.
Note: This must be set higher than the cylinder thermostat to achieve the cylinder set temperature.
Winter setting - In this mode the boiler will operate in both heating and hot water mode according to the control requests.
With the Alpha Diverter kit fitted the heating of the cylinder takes priority over heating and once the cylinder set temperature
is reached the boiler will revert to heating if rquired according to the temperature set on the boiler heating control knob.
Note: This is the radiator water temperature and not room temperature.
With the DHW relay option the boiler will operate according to the external control request for either heating or hot water or
both. When a request for heating the hot water cylinder is given, the water temperature for both heating and hot water will
be the at the set point of the hot water control knob of the boiler reverting to the heating control knob temperature once the
cylinder reaches the thermostat set point and heating is requested.
For a system fitted with a standard S or Y plan layout with external controls the boiler should always be left in winter mode.
During operation the boiler LCD will display the temperature of the water leaving the boiler.
Note: When using a standard Y or S plan system the central heating water temperature must be set above the
cylinder thermostat value using the central heating control knob 6 in Fig. 1.
External weather compensation sensor (only for use with the Alpha Diverter Kit or Relay unit) - The temperature of
the central heating water can be adjusted by using the central heating buttons (items 6 and 7 in Fig. 1). When the heating is
on the temperature of the water leaving the boiler to the radiators will be displayed.
If an external weather compensation sensor is fitted, indicated by the
symbol (item 18 in Fig. 1) in the display, it will
automatically vary the temperature of the water in the radiators and on mild day the radiators will not feel as hot as on a cold
day, this is normal and not a fault with the boiler or heating circuit. The room temperature will still be maintained as set by the
room thermostat.
When an external weather sensor is fitted, the central heating control knob (item 5 in Fig. 1) 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 2
i.e. line 6 will give a flow temperature of 60°C when the external temperature is 10°C.
Note: This is the temperature of the water supplied to the radiators and not the desired room temperature. The time and
temperature will still be maintained according to the setting of the room thermostat.
3 HEATING AND HOT WATER TEMPERATURE
Fig. 2 - External weather compensation sensor fitted
Flow temperature (°C)
External temperature (°C)
27 15
5
-510 0 -10 -1520
25 (25)
60 (40)
80 (50)
Flow temperature in brackets
ie. 25 to 50°C range when boiler
is used with a low temperature
system such as under floor heating
Setting 1 to 9 as selected using
the central heating selector switch
The boiler has a built in frost protection function to protect the boiler (only) from freezing. If water within the boiler
falls below 4°C the boiler will fire in heating mode and raise the temperature of the heating water (in the boiler only)
to 42°C. If the circulation pump is connected to terminal L2 and N2 the pump will be active during frost protection
mode.
For this function to be active the gas and electricity supplies to the boiler must be turned on and the boiler be in either
'Standby' or 'On' mode and the frost protection enabled in the boiler parameters.
Further protection for the mains water supply and heating circuit must be provided separately.
If Alpha external controls are fitted, a frost protection setting is incorporated into the room thermostat activating the central
heating when the temperature falls below 5°C.
4 FROST PROTECTION
Alpha E-Tec 15, 20, 25R
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