GE Mark VIe System Manual page 148

6.6.3 Cable Routing Guidelines
6.6.3.1 Pullboxes and Junction Boxes
Keep signal and power levels separate inside pullboxes and junction boxes. Use grounded steel barriers to maintain level
spacing. Tray-to-conduit transition spacing and separation are a potential source of noise. Be sure to cross unlike levels at
right angles and maintain required separation. Use level spacing. Protect transition areas according to the level spacing
recommendations.
6.6.3.2 Transitional Areas
When entering or leaving conduit or trays, ensure cables of unlike levels are not mixed. If the installation needs parallel runs
over 1.5 m (5 ft), grounded steel barriers may be needed for proper level separation.
6.6.3.3 Cabling for Retrofits
Reducing electrical noise on retrofits requires careful planning. Lower and higher levels should never encircle each other or
run parallel for long distances. It is practical to use existing conduit or trays as long as the level spacing can be maintained for
the full length of the run. Existing cables are generally of high voltage potential and noise producing. Therefore, route levels
L and M in a path apart from existing cables when possible. Use barriers in existing pullboxes and junction boxes for level L
wiring to minimize noise potential. Do not loop level L signals around high control or level P conduit or trays.
6.6.3.4 Conduit Around and Through Machinery Housing
Care should be taken to plan level spacing on both embedded and exposed conduit in and around machinery. Runs containing
mixed levels should be minimized to 1.5 m (5 ft) or less overall. Conduit running through and attached to machinery housing
should follow level spacing recommendations. This should be discussed with the contractor early in the project.
Trunnions entering floor mounted operator station cabinets should be kept as short as possible when used as cableways. This
helps minimize parallel runs of unlike levels to a maximum of 1.5 m (5 ft) before entering the equipment. Where different
signal/power levels are running together for short distances, each level should be connected by cord ties, barriers, or some
logical method to prevent intermixing.
6.6.3.5 RF Interference
To prevent radio frequency (RF) interference, take care when routing power cables near radio-controlled devices (for
example, cranes) and audio/visual systems (public address and closed-circuit television systems).
6.6.3.6 Suppression
Unless specifically noted otherwise, suppression (for example, a snubber) is required on all inductive devices controlled by an
output. This suppression minimizes noise and prevents damage caused by electrical surges. Standard relay and solenoid
output boards have adequate suppression.
148 GEH-6721_Vol_I_BP GEH-6721_Vol_I Mark VIe and Mark VIeS Control Systems Volume I
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