EN
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4
OPERATION
4.1 General
The Megaflex is a floor standing boiler, equipped with a cast aluminium heat-exchanger. During heat
demand the controller activates the pump. The controller checks the air pressure switch (zero check)
and increases the fan speed to perform an airflow-check. Once the air pressure switch closes, the fan
speed increases to ignition speed and a 5 second pre-purge is performed. The water pressure sensor, gas
pressure switch and siphon pressure switch are checked. When all pressure switches are closed and the
water pressure is ok, the ignition is started.
The air needed for combustion is taken in from the outside (if room sealed) or the boiler house (type
B flue installation) by the fan. The air is transported through a gas/air mixing device creating a negative
pressure. This negative pressure is an indication of the amount of air being transported. The negative
pressure is supplied to the gas valve by an internal tube. The gas valve automatically adjusts the amount
of gas that will be injected into the venturi and that will be mixed with the air-flow. This mixture is
supplied to the burner.
Ignition and flame-control of the mixture is done by two electrodes mounted on the burnerhood.
Temperature control and safeguarding is done using two NTC’s. The boiler monitors the sensors
continuously in order to control operation and ensure safe operation.
4.2 Central Heating (CH)
4.2.1 On-off room thermostat
As standard the boiler is programmed for using an on-off room thermostat. The room thermostat has to
be connected to the pin nrs. 1 + 2 on the terminal strip. Open Therm will be recognized if connected on
1 + 2. The desired flow temperature is adjustable, but as standard is set to 85 °C.
At CH heat request from the room thermostat (and no DHW heat request present) the CH-pump
is activated after 10 seconds. The controller will adjust the burner-input in such a way that a flow-
temperature of 85 °C towards the CH-circuit is achieved.
Warning : do not supply any voltage to these terminals as you may damage the controller
4.2.2 Optional 0-10V
The boiler may be controlled using a 0-10 V DC signal. Connect the negative (0V DC) to No. 3, and the
positive (0-10V DC) to No.4 on terminal strip C2.
A loop of wire must be placed between the pin nrs. 1 and 2 of terminal strip C2.
In the technician menu, enable 0-10V in the advanced CH settings menu by setting, CH request to either
0-10V DC % or 0-10V DC SP.
4.2.2.1 0-10V DC % power control
A value between 2 and 10V DC generates a CH power demand proportional to this value between 0
and 100% (0% = minimum load, 100% = nominal load). The heat demand is removed when the control
signal falls below 1 volt.
The setpoint of maximum flow temperature is set to 90°C.
In the user/technician menu, under diagnostics, boiler information the actual voltage input and target
power are displayed.
4.2.2.2 0-10V DC Setpoint
A value between 2 and 10V DC generates a CH setpoint demand proportional to this value between
CH minimum flow temperature and maximum CH flow temperature. The heat demand is removed when
the control signal falls below 1 volt.
The minimum and maximum CH flow temperature can be set in the technician menu, advanced CH
settings, CH temperatures.
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