WIKA T53 - Manual (Page 29)

GB
11178648.04 03/2010 GB/D/F/E
WIKA Operating Instructions Temperature Transmitter T53 29
The Nonincendive Field Wiring concept allows the interconnection of nonincendive field
wiring apparatus using any of the wiring methods permitted for unclassified locations.
V
max
>= V
oc
or V
t
, C
a
>= C
i
+C
cable
, L
a
>= L
i
+ L
cable
“
The Nonincendive Field Wiring concept allows the interconnection of FM-approved
nonincendive devices with FNICO parameters not specifically examined in combination
as a system when: U
o
or V
oc
or V
t
<= V
max
, P
o
<= P
i
In each I.S. Fieldbus segment only one active source, normally the associated apparatus,
is allowed to provide the necessary power for the Fieldbus system. The allowed voltage
(U
o
, V
oc
, V
t
) of the associated apparatus used to supply the bus must be limited to the
range of 14 V d.c. to 24 V d.c. All other equipment connected to the bus cable has to
be passive, meaning that the apparatus is not allowed to provide energy to the system,
except to a leakage current of 50 A for each connected device. Separately powered
equipment needs a galvanic isolation to insure that the intrinsically safe Fieldbus circuit
remains passive.
The cable used to interconnect the devices needs to comply with the following parameters:
Loop resistance R': 15 ...150 /Km
Inductance per unit length L‘: 0.4…1 mH/km
Capacitance per unit length C‘: 80 ...200 nF/km
C‘ = C‘ line/line + 0.5 C‘ line/screen, if both lines are floating
or
C‘= C‘ line/line + C‘ line/screen, if the screen is connected to one line
Length of spur Cable: max. 30 m
Length of trunk cable: max. 1 Km
Length of splice: max. 1 m
Terminators
At each end of the trunk cable an approved line terminator with the following parameters
is suitable:
R = 90 ...100 Ω
C = 0 ... 2.2 µF
System evaluation
The number of passive devices like transmitters, actuators, connected to a single bus
segment is not limited due to I.S. or N.I. reasons. Furthermore, if the above rules are re-
spected, the inductance and capacitance of the cable need not to be considered and will
not impair the intrinsic safety or nonincendive safety of the installation as applicable.
The sensor circuit is not infallibly galvanically isolated from the Fieldbus input circuit. Ho-
wever, the galvanic isolation between the circuits is capable of withstanding a test voltage
of 500 V
ac
during 1 minute.
Appendix 1: FM-CSA Installation Drawing
5/6
Installation Drawing 11175631.01