Technical information

switches back to low speed. When the
heating demand is removed, the pump
continues to run for the pre-set overrun
time, at the end of which it is switched off.
24.5 8.1.5 Frost protection
If the temperature detected by the supply
sensor falls below 8 °C, the pump will be
switched on and will circulate water through
the central heating circuit. If the temperature
detected by the supply sensor falls below
3 °C, the burner will be ignited. As soon as
the return temperature reaches 15 °C, the
burner will be switched off. The pump will
continue to run for the pre-set overrun time.
It is also possible to set the pump to run
continuously.
24.6 Weather compensation
This function is only available if the optional
external sensor is connected. The external
temperature control determines the
optimum set value of the central heating
temperature in relation to the prevailing
external temperature.
2
3
5
4
1
24.7 Setting the Heat Slopes
Depending on the installation, determine the
maximum supply temperature for the lowest
expected external temperature (set-point
T
central heating max
).
Draw a horizontal line at this central heating
temperature to the point where it intersects
the external temperature concerned (point
(1) in the foregoing graph).
Determine the minimum desired central
heating temperature (T
basis
= O/b). and draw
a horizontal line at this value.
Determine T
ref. day
. This is the desired central
heating temperature for an external
temperature of 20 °C. Mark a point (3) by
the values concerned.
Draw a line between points (1) and (3).
The point where this line cuts T
basis
is point
(2).
Draw vertical lines from point (1) and from
point (2) to the x-axis. The points of
intersection with the x-axis are points (4)
and (5) respectively.
The S-factors can now be determined by
dividing the difference between T
central heating
max
and T
basis
by the difference in external
temperature represented by points (5) and
(4):
- T
central heating max
- T
basis
O/S = -------------------- x 10
T
(5)
– T
(4)
The foregoing example follows from a
T
central heating max
of 80 °C, a T
basis
of 50 °C and
a T
ref day
of 30 °C for an external
temperature of 20 °C and gives an O/S of
20.
Next you will find a number of empty graphs
that you can fill in yourself.
EC 25 Compact Installation/User Manual page
37