Cabling; Power Requirements - Honeywell 5704 Operating Instructions Manual

MAN0448_Issue 13_01-2010
005704-M-5001 A03249
CHAPTER 4 - INSTAllATION INSTRUCTIONS
4.

CABlING

The field terminals on the Quad Relay Interface and Relay Interface
Assembly accept single or multi-stranded wire up to 2.5mm˝ (14 AWG).
Cables should be routed carefully to avoid physical and environmental
hazards such as mechanical stress and high temperatures.
Sensor wiring should consist of a cable with an earthed outer shield
and should be routed away from sources of interference such as ac
power cables, motors, machinery etc. All sensor cabling is subject to a
maximum cable length that is dependant upon the cable line resistance
and sensor types.
The current ratings of the power and relay cables should always be
higher than the worst case maximum load requirement.
All sensor field cables must be screened in order to ensure correct
operation of the system and to meet European Standards for RFI and
EMC. The cable screen of each sensor should be connected to a
GROUND terminal at the cabinet entry or the ground terminal of the
appropriate Quad Relay Interface Card or another suitable ground
point.
5.

POWER REQUIREMENTS

The System 57 operates from a nominal 24V (18V to 32V) dc power
supply input which may be derived from various sources including the
mains ac, via a separate ac to dc power supply unit, local plant dc
supply and/or battery backup dc supply.
The power supply may be applied to the System 57 backplane, via the
DC Input Card, where the maximum backplane current is limited to 8A.
The DC Input Card terminal blocks allow flexible power connections
and diode isolation for two separate power supply inputs.
Where the number of Four Channel Control Cards fitted and the type
of sensors used would cause a backplane current in excess of the
8A maximum, it is necessary to connect the power supply to each
individual control card via its Quad Relay Interface Card. As a general
rule, individually powered cards are required where more than eight
catalytic control cards are fitted.
See Section 17 for connection details.
The power supply rating required is dependent upon the sensor types,
number of channels and configuration of the System 57. Table 1, the
Power Budget Calculation Sheet, allows for a quick and easy calculation
of the worst case power requirement for the system. In many cases a
lower power rating can be used, however, a more detailed power budget
4-7
5704 Control System