Crowcon Xgard Installations- Und Sicherheitsanweisungen Seite 28

Xgard and Xgard IR
of detectors should be recorded.
Guidance for the selection and location of gas detectors is provided in BS EN 60079-
29-2:2015 'Explosive atmospheres. Gas detectors. Selection, installation, use and
maintenance of detectors for flammable gases and oxygen'.
3.4 Mounting
Xgard should be installed at the designated location with the sensor pointing down. This
ensures that dust or water will not collect on the sinter/sensor and stop gas entering
the cell. Care should be taken when installing aluminium versions of Xgard to avoid
damaging the painted surface of the junction box and sensor retainer.
3.5 Cabling
Cabling to Xgard must be in accordance with the recognised standards of the appro-
priate authority in the country concerned and meet the electrical requirements of the
detector.
Crowcon recommend the use of steel wire armoured (SWA) cable; suitable Exd
Flameproof glands must be used for Xgard Types 2,3,4,5,IR. Alternative cabling tech-
niques, such as steel conduit, may be acceptable provided appropriate standards are
met.
Shielded cables should be used, grounded at one end only to prevent the risk of signal
interference.
The acceptable cross sectional area of cable used is 0.5 to 2.5 mm 2 .
Maximum cable distances can be calculated factoring: the resistance of the specific
cable used, the supply voltage, the minimum operating voltage of the Xgard detector.
For Xgard Type 1; the I.S. barrier characteristics and cable capacitance/inductance
must also be considered. Examples are shown in the full Xgard manuals available on
the Crowcon website.
3.6 Connections and earthing requirements
Connections are made via the screw terminal block mounted on the amplifier PCB in
the junction box. Correct polarity must be observed when connecting the detector to
control equipment.
The internal grounding terminal (see Diagram 5, page 10) shall be used as the ground-
ing means of the Xgard gas detector. The external grounding terminal is only a sup-
plemental bonding connection, and is only to be used where local authorities permit or
require such a connection. To limit radio frequency interference, the junction box and
cable armour should be grounded (earthed) at the control panel. Ensure the earth con-
nection is in a safe area only, so as to avoid earth loops.
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