PC3000 Complete Installation guide iss 12 - Elektro-Trading

PC3000 Installation Guide
Appendix A
include the separation described above.
The AC supply to all the modules fitted to the rack, should be taken from as close to
the in-coming source as possible and should not under any circumstances be “daisy
chained” from other equipment, especially if it is likely to generate supply borne,
electrical noise.
For digital communications, it is strongly recommended that screened cable is used
and that only one end of the screen is earthed at the “cleanest” end, usually at the
computer. The screened cable should be routed with the control wiring. Do not use
‘spare’ wires in the cable for other signals.
It is essential that communications, control and power wiring are routed separately
through the cabinets and plant.
Earthing
All earth terminals must be securely connected directly to a good local earth by
conductors appropriate to the current ratings of the modules.
Any Input/Output module provided with a filter return connection must be connected
to a low impedance earth point conforming to local wiring standards. Connections
must not be routed to earth via the rack chassis and earth stud connection.
Before switching on PC3000, the protective earth terminal, located on the left hand
side of the rack, must be connected to a protective conductor i.e. a low impedance
earth point.
WARNING
Any interruption of the protective conductor inside or outside
PC3000 or disconnection of the protective earth terminal could
potentially make the apparatus dangerous. Intentional interruption is
prohibited.
Most Eurotherm Controls instruments have internal circuits which are
isolated or “floating”. This is necessary to prevent the occurrence of
an “earth loop” in signal circuits. To avoid possible shock hazards in
the event of an internal fault causing breakdown of insulation, it is
recommended that all equipment connected to any PC 3000 module
be enclosed in an earthed metal enclosure. Sheaths of thermocouples
(or other sensors) should be properly earthed by a separate conductor
(instead of being dependent on earthing via the machine framework).
The top and bottom covers together with the rear cover on the
PC3000 rack, form an integral part of the earthing system and should
not be removed. Additionally, the rack fascia fixings must be
quarter-turn tightened following replacement.
App.A-3
Appendices