Mounting and Installation
16
161936 / 941160310020
2015-09-15·BA00·III·en·08
Zone 1 Ex e field device coupler
Series 9411/11
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8.3.2 Cable Lengths for Trunk and Spurs
The basis for measuring cable lengths for the trunk and spurs is IEC 61158-2, Annex B
(without taking into account explosion protection).
Note the following points when laying cables:
• The maximum length of all cables (all trunks, all spurs) per segment must not exceed
1900 m.
• The actual trunk and spur lengths can be shorter due to voltage drop.
• The following generally applies: Spurs should be kept as short as possible.
Maximum spur length = 120 m.
8.3.3 Earthing
Field device coupler without enclosure
The field device coupler does not need to be connected to earth.
Field device coupler installed in a metal field enclosure
Earth the enclosure via the shortest possible route.
Earthing of cable shields
The cable shields must be earthed before use.
The following regulations exist in relation to earthing cable shields:
• IEC/EN 60079-14, Section 12.2.2.3
• Profibus Technical Guideline "Profibus PA" User and Installation Guideline,
Section 3.3.3
• Fieldbus FoundationTM "System Engineering Guidelines" AG 181, V3.1f
DANGER
Explosion hazard caused by interference voltages in the cable shield,
Non-compliance can result in severe or fatal injuries.
• Earth the shields.
