TESTO 300 - Page 84

14 Performing the measurement
82
derogations are possible. An underpressure of more than 4 Pa should be
regarded as dangerous when operating firing installations which are dependent
on indoor air. When operating tested firing installations which are not dependent
on indoor air for solid fuels, as a rule an underpressure of more than 8 Pa is not
permissible (see proof of usability e.g. general building approval for the firing
installation). These test guidelines apply to differential pressure measuring
instruments for determining the underpressure in rooms where firing installations
are set up and is aimed at the manufacturers of these kinds of measuring
instruments. They set out requirements for construction and minimum
requirements for the performance characteristics of relevant measurement and
inspection equipment in the area of underpressure measurement, along with
specifications for carrying out qualification tests.
Description of typical measuring principles:
With an instrument that has been tested according to these guidelines, it is
possible to check an underpressure limit value of 4 Pa, or of 8 Pa for firing
installations which are not dependent on indoor air, in the equipment room, and
to show the time progression over a period of at least 3 minutes in a diagram on
the display, or to print it out, and evaluate it. Two flexible capillary hoses of the
same length enable the differential pressure between the equipment room and a
reference point that is pneumatically disconnected from the combustion air
network (outside air, stairwell) to be recorded and conveyed to a pressure
sensor.
The capillaries can be routed both outside through the window sealing and to
the stairwell through the door rebate or the keyhole. The second capillary hose
remains in full in the equipment room.
Procedure for an underpressure measurement in equipment rooms:
Firing installations which are dependent on indoor air must not be set up in
rooms with air extraction equipment. However, insofar as no dangerous
underpressure can arise while the firing installations are in operation,
derogations are possible. An underpressure of more than 4 Pa should be
regarded as dangerous when operating firing installations which are dependent
on indoor air. When operating tested firing installations which are not dependent
on indoor air for solid fuels, as a rule an underpressure of more than 8 Pa is not
permissible (see proof of usability e.g. general building approval for the firing
installation).
The proof can be provided through different measures. These for instance
include the installation of a window tilt switch, the installation of an
underpressure monitor or proof by means of measuring technology that with
simultaneous operation of the fire installation(s) and indoor air extraction
system(s), no dangerous underpressure can arise.
The question as to which measure may give the desired result essentially
depends on the local conditions. These are for instance the leaktightness of the
building shell, the size of the usage unit, the presence or leaktightness of the
communicating doors and the quantity of air which is extracted from the usage
unit by the indoor air extraction systems.