13.2
High temperature protection
The maximum temperature protection is
obtained with the aid of the supply and
return sensors. If one of these sensors
registers a temperature in excess of 93 °C,
the burner will always be switched off.
If one of these sensors registers a
temperature in excess of 105 °C, the control
system blocks all further heating demand
and starts pumping through the central
heating circuit in order to remove the
superfluous heat as quickly as possible. ‘H’
appears in the status display and the
temperature display will show the supply
temperature.
If during burning, one of these sensors
registers a temperature in excess of 105 °C,
the appliance will be immediately blocked
with a flashing ‘H’ on the status display and
the supply temperature on the temperature
display. Pressing the reset pushbutton on
the display can only discontinue this
blocking. With a temperature in excess of
118 °C,
will be displayed.
The control system will then perform the
following three measurements.
1.
Before the control system ignites the
burner, the difference between supply and
return temperatures must be less than
20°C.
2.
The following check measurement
will be carried out each time the burner is
ignited. Both the supply temperature and
the
∆
T will be measured just before the
burner is ignited. If the control system does
not detect an increase of three degrees in
the supply temperature or in
∆
T after 10
seconds of burning, the burner will be
immediately shut down. The control system
will wait until
∆
T is less than 5 °C and (if
there still a demand) will then make another
attempt at ignition. If this test is not
successful after three attempts, the control
system will block further operation with a
flashing ‘2' on the status display and the
supply temperature on the temperature
display.
Once in every two hours the difference
between supply and return temperatures
must have been less than 5 °C. Is this not
the case, than the burner will not be ignited
until this is the case. While the system is
waiting for this condition to occur, the status
display will show a ‘2' continuously, and the
temperature display will show the supply
temperature. A combustion cycle will not be
interrupted by this protection.
13.3
Static pressure
The static pressure P in the appliance is
monitored. The following situations can
occur:
P <= 0.2 bar
All heating demand will be blocked, the
pump will be switched off and the status
display will show a P continuously.
The static pressure will be shown in the
temperature display. This is a indication that
the user must top up the appliance.
The blocking will only be discontinued when
the pressure exceeds 1.3 bar. This offers
the possibility to read the pressure in the
appliance during topping up.
0.2 bar < P < 0.5 bar
The capacity of the appliance is limited to
low load so that the user can still obtain
heat, but because of a reduced level of
comfort will realise that something is not in
order. In the status display, the letter
indicating the condition of the appliance
(rest, central heating use or hot water
operation) will alternate with ‘P’. The
temperature display will show the system
pressure. This condition will be discontinued
as soon as the pressure exceeds 1.3 bar.
P > 0.5 bar
The appliance will function without
limitations
P > 3.5 bar
All heating demand will be blocked and the
pump will be switched off. This blocking will
only be discontinued when the pressure
falls below 3.0 bar. The pressure can be
read from the display.
EC 25 Compact Technical Manual page
23