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GENERAL INFORMATION INSTALLATION OF SHIPS INSTRUMENTATION CABLESPage 1 of 2

J. Lilley and Gillie Ltd. Ref: 7070/ccg/ra/139 Issue 1

1.0 General Information Installation of Cables.

Low voltage cables can normally be split into at least four classes where each class runs along a

different route, only bundled with, or in close proximity to, cables from its own class.Cable classes would ideally not cross over each other but where they must cross, they should do so at

right angles. If classes are more than one class apart additional metal screening may be required

where crossing occurs.

1.1 Cable classes.

Class 1 is for cables carrying very sensitive signals. Low level analogue signals such as millivolt

output transducers (i.e. the Walker log transducer) and radio receiver antennae are in Class 1A. High-rate digital communications such as Ethernets are in class 1B. Classes 1A and 1B should not be

bundled together, although their bundles may be run adjacent to each other.

Class 2 is for cables carrying slightly sensitive signals, such as ordinary analogue (i.e. 4-20mA, 0-

10v and signals under 1MHz), low rate digital communications (i.e. RS422, RS485), and digital (i.e.

on/off) inputs and outputs (e.g. limit switches, encoders, control signals). Cables carrying NMEA

0183 serial data, or other available analogue signals, from the 7070 master unit are included in thisclass, as are the connecting cables from the Walker Wind Sensors, Weather Sensor and Water

Temperature Sensor.

Class 3 is for cables carrying slightly interfering signals, such as low voltage AC distribution (

7/28/2019 7070-ccg-ra-139_Iss_1

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GENERAL INFORMATION INSTALLATION OF SHIPS INSTRUMENTATION CABLESPage 2 of 2

J. Lilley and Gillie Ltd. Ref: 7070/ccg/ra/139 Issue 1

1.2 Segregation distances

Recommended minimum spacings between cable classes, based on a 30 metre run of cables held

close within a parallel earth conductor (PEC) which could be a tray, open (or closed) duct or solid

metal conduit are shown in the diagram below.Longer parallel runs should use pro-rata greater spacings. Note that if longer runs are involved,

multiply the stated spacings by a factor given by: length (in metres) 30.

CLASS 1 CLASS 2 CLASS 3 CLASS 4

cables cables cables cables

PEC (parallel earth conductor) e.g. cable tray

Class 5 cables are not shown in the diagram above but should be at least 150mm spacing from Class

4, with Class 6 at least a further 150mm away. Where any such MV or HV cable is within 1 metre of

a Class 1 cable, the Class 1 cable should be run in a covered metal duct.

Greater spacings generally give lower coupling (crosstalk) between cables; however the acceptable

amounts of coupling will always depend on the types of cables, the installation techniques used, the

electronics connected to each end of the cables and the functional requirements of the application.

Running individual cable classes in their own closed metal duct or round conduit PECs allows the

spacing between classes to be reduced (even to zero), but it is still best to avoid running classes 1 and

4 close together.

Note that type approved equipment that includes IEC60945 certificated accreditation will be immune

from interference levels stated in the standard, providing that the installation of the said equipment

has been carried out strictly in accordance with manufacturers instructions.

150mm150mm 300mm

450mm

450mm

600mm