Technical information

23.2
Flue System Check
In order to examine the flue pipe sealing,
with the boiler running, it is essential that an
O
2
or CO
2
reading is taken from the sample
point 3 (fig 21) positioned on the left of the
concentric adaptor.
The flue seal is satisfactory when the CO
2
value is no more than 0.2% and the O
2
value no more than 20.6%.
Figure 22 Sample Points
24. Control Setup
24.1
External temperature control
During central heating use the capacity of
the appliance is adjusted continuously to
match the heating demand, so that the flow
temperature (T
central heating
) is variable
between 20 and 90 °C.
The on/off signal from the room thermostat
is converted into a modulating heating
demand by the on board digital control
system (by means of the applicable
algorithm T
central heating
).
24.2 Switching on the appliance
Turn on the appliance using the on/off
switch located underneath the boiler casing
to the right of the casing latch.
With a closed room thermostat and a
difference between the set value T
central heating
and a water temperature of more than
10°C, the burner will be ignited.
The status display will show ‘C’ if the central
heating water temperature increases by 3°C
above T
central heating
, the burner will stop
burning, while the pump will continue to run.
The status display will show ‘C’.
When the room thermostat opens, the
overrun function of the pump will be started.
While the pump continues to run, the status
display will show ‘c’. The overrun time for
central heating operation and the set value
T
central heating
can be set using the keys on the
display.
24.3 Setting the Output
When the room thermostat is closed and the
burner is ignited the capacity is modulated
between minimum and maximum capacity
by means of a variable fan speed.
As soon as the burner is ignited, it will
remain at the starting speed for the first
minute.
At the end of this 10 second period the
burner will switch to low load for 10 minutes.
Thereafter, the capacity will be increased in
a linear manner.
When the supply temperature is 30°C below
T
central heating
the control system will switch
immediately to a linear increase in the
capacity. Shortly before reaching the
maximum set capacity, the appliance will
start modulating.
From the moment that the measured central
heating temperature t
central heating
reaches the
set point T
central heating
, the temperature will be
controlled by the opening and closing of the
room thermostat.
The maximum burner capacity is limited by
the minimum central heating water
circulation through the appliance.
24.4 Pump operation
The pump has two speeds: low (1750 rpm)
and high (2200 rpm). Normally the pump
runs at low speed. When a value for
∆
t of
30 °C is reached, the pump switches to high
speed. If
∆
t is lower than 10 °C, the pump
Page 36 ECO HOMETEC
(
UK
)
LTD
.