Design Information | 3
M1820921_en | Installation instructions Dual fuel boiler SP Dual compact
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3.5.2 Simultaneous operation with other air-drawing systems
Where the boiler is operated in room air-dependent mode with simultaneous operation of
other air-drawing systems (such as room ventilation), safety devices are necessary:
▪ Air pressure monitor
▪ Flue gas thermostat
▪ Window-tilting drive system, window-tilting switch
NOTICE! Clarify the safety devices with appropriate flue sweep / chimney sweep
Recommendation for room ventilation:
Use “intrinsically-safe” room ventilation systems with F classification
As a basic rule:
▪ Room under-pressure max. 8 Pa
▪ Air-drawing systems must not exceed the room under-pressure value
– If the room under-pressure value is exceeded, safety equipment (under-pressure
monitoring system) is necessary
In Germany, the following additional requirement must be observed:
DiBt requires that an approved under-pressure monitoring system (such as air pressure
monitor P4) which monitor the maximum under-pressure to 4 Pa must be installed in the
installation room.
In addition, at least one of the following three requirements must be met:
(Source: Section 4 MFeuV 2007 / 2010)
▪ Dimension the cross-section of the combustion air opening so that when the boiler is
in operation the maximum under-pressure is not exceeded (simultaneous operation)
▪ Use safety equipment that prevents simultaneous operation (alternate operation)
▪ Monitor the flue gas outlet using safety devices (such as a flue gas thermostat)
Simultaneous operation
An approved safety system (such as an air pressure monitor) ensures that during
simultaneous operation of the boiler and the air-drawing appliance the pressure
conditions are maintained. In the event of a fault, the safety system will switch off one of
the air-drawing systems.
Alternating operation
An approved safety system (such as a flue gas thermostat) ensures (e.g. by switching off
the power supply) that the boiler cannot be operated simultaneously with the air-drawing
appliance.
