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4. APPLIANCE OPERATION
4.1 Generality
The unit can heat (in winter) as well as ventilate (in summer). By using the temperature-sensor on the
unit and the one in the room-thermostat, the temperature-difference between the two in the room is
monitored (see chapter 4.3).
If the desired temperature is not reached, the appliance will heat. The modulating burner gives the
exact quantity of necessary heat to reach a comfortable temperature.
4.2 Heat demand
If the thermostat indicates heat demand, the following cycle will start:
1) Pre-purge :
The electronic circuit board acknowledges the heat-demand and the premix
burner fan will start running for 30 seconds.
2) Ignition :
After 30 seconds of pre purge the electrode will spark for max. 5 seconds, the
gas valve is opened and the gas-air mixture will ignite
The display of the control print board indicates 2.
If the air/gas mix is not lighted or if there is no flame detected, the control print board start a second
ignition attempt before be in security state.
In this case, the display of the control print board indicates alternatively A and 1.
3) Heating :
Once the flame is detected, the unit will modulate to the desired load after 15 seconds.
The display of the control print board indicates b.
Depending on the given load, the system fan will start modulating (step-less) as well. The air heater
will always burn for a minimum of 4 minutes. This is to evaporate eventual condensation in the
discharge system.
4) End of heat demand :
When the heat demand ends, the burner will switch off and the system fan will continue to run for
around 3 minutes in order to cool the unit down
The display of the control print board indicates P.
The unit will try to ignite twice before lockout on flame fault. In the case of flame failure during
operation, the heater will attempt one restart.
When the heater is in lockout you see in the display intermittent an A and 1. On the display of the
MULTITHERM you will see failure 1.
4.3 Delta-T regulation (de-stratification fan mode)
When the difference of temperatures between the sensor on the unit (the NTC) and the sensor in the
MULTITHERM is bigger than the set value (factory setting standard 8°C), the burner is turning off and
only the main fan will operate at a regulated speed depending on the differential temperature
difference. This operation ensures an even temperature distribution throughout the building, thus
acting as a fully automatic variable de-stratification fan.
The Delta-T mode is working only in combination with the MULTITERM thermostat.
If you don't desire to use the Delta-T regulation, it is possible to disable it in the parameters menu of
the MULTITHERM. See the technical instructions of the MULTITHERM.
4.4 Summer ventilation
It is possible to ventilate the ambient air with the AM unit independently from the heat demand through
the summer ventilation function of the MULTITHERM S or C. The summer ventilation can be set on 3
different speeds, see the technical instructions of the MULTITHERM.
The display of the control print board indicates 1.
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