Technical information

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.
25.4 Hot Water Cylinder
A hot water cylinder boiler can be directly
connected to the EC25HS. The cylinder
temperature can be regulated by means of
a thermostat or an NTC temperature
sensor. When an NTC-sensor is used, the
appliance will modulate during the boiler
heating cycle. In the following process
description it is assumed that regulation
takes place by means of an NTC-sensor.
The NTC sensor measures the temperature
of the cold water supply. The hot water
cylinder is heated when the temperature
falls 5°C below the set temperature or the
temperature drops greater than 1°C per
minute.
As soon as there is a demand, the burner
will be ignited. The burner modulates the
return temperature to the set value T
ext_boiler.
(temp. of the hot water cylinder) The status
display shows ‘b’. T
ext_boiler
can be set with
the aid of the keys on the display.
The burner will be switched off when:
t
supply
> T
central heating max
t
return
> T
ext_boiler +
5°C
When the burner is off and there is still a
heating demand, the appliance will continue
to circulate water through the boiler circuit
until the return temperature falls below
T
ext_boiler
- 5 °C. The status display shows ‘b’.
When t
cold
is higher than T
ext_boiler
-5 °C, the
heating demand will be removed and the
pump-overrun function for external-boiler
operation will be activated (30 seconds
overrun pumping via the boiler circuit).
The status display then shows ‘b’.
26. Safety devices
26.1 Electronic ignition
The electronic ignition is protected against
overload. The maximum glow time per
ignition is 7 seconds (2 seconds pre-
incandescence and 5 seconds in the
ignition phase). The incandescent ignition
can be operated a maximum of 5 times in a
short period. After these 5 attempts the
control system allows 1 ignition attempt
every minute. When the electronic ignition is
not used for 5 consecutive minutes, 5
consecutive ignition attempts will again be
possible. When the ignition of the burner is
delayed by the control system, the status
symbol changes to an 'o'.
26.2 Flow protection
The appliance is provided with a water
pressure sensor, which is used in
combination with the supply and return
sensors to protect the appliance against a
no flow situation.
For every burner start, the pump is stopped
and after a 2 second delay the static system
pressure is measured. Hereafter the pump
is restarted at high speed. The fan runs and
the pre-incandescence phase begins.
At the end of the ignition phase the system
pressure is measured again.
The following situations are possible:
Pressure difference < 0.06 bar:
1. Air in the appliance
Pump or pump connection is broken. The
control system switches to the pump test
phase, in which the pump is switched on for
30 seconds and then off for 30 seconds.
During this test phase the control system
waits until a sufficient pressure difference is
created. The display shows ‘P’ continuously
and all heating demands are disregarded.
Pressure difference > 0.44 bar:
Too little flow. In this case the control
system also switches to the pump test
phase. During this test phase the control
system continues to wait until the pressure
difference is between 0.06 and 0.44 bar.
Pressure difference > 0.06 and < 0.44 bar:
The burner ignites and the flow monitoring
is taken over by the supply and return
sensor logic.
The pump is forced to switch over to low
speed until there is an increase in
temperature. In this way the pump is tested
EC 25 Compact Installation/User Manual page
39