TESTO 300 LL NEXT LEVEL Instruction Manual page 77

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.
It can be assumed that, with effective fume hood systems, at least 400 m
air are extracted (with exhaust air driers the quantity of air is not significantly
below this, very powerful fume hood systems extract over 1000 m
With very high air extraction performances, an underpressure measurement is
frequently not expedient in apartments or comparable usage units.
As a rule, the solution here can simply be an opening to the outside, so for
example a tilted window with a window tilt switch. In a case of this kind, the
measurement only makes sense if the owner/operator of the firing installation is
absolutely intent on having the proof of the underpressure being too high.
The area of application of underpressure measurement in equipment rooms is
therefore primarily where the power of the indoor air extraction systems is
estimated to be low or there are particular physical conditions which suggest
that the underpressure does not exceed the permissible value (4 or 8 Pa) when
the firing installation(s) and indoor air extraction system(s) are operated
together.
The check that no dangerous underpressure can arise should be carried out
using pressure measuring instruments that have undergone qualification testing
for the "measurement of underpressures in rooms where firing installations are
set up".
The measurement is carried out according to the following process outline:
1. Close all the usage unit's windows and doors. If there are blinds present on
the windows and external doors, these should also be closed. Switch
differential pressure measuring instrument on and wait for the zero point to
be determined, connect capillary hoses to the measuring instrument
(reference = (-) connection, equipment room = (+) connection), open
9 Performing the measurement
/h of
3
3 /h of air).
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