Halma Ampac Orbis IS ORB-OP-52027-APO, Product Manual

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MAN3041-1
21
11 Wiring and cable types
It is not permitted to connect more than one circuit in the hazardous area to any one safety barrier and
that circuit may not be connected to any other electrical circuit. Both separate and twin cables may be
used. A pair contained in a type ‘A’ or ‘B’ multi -core cable (as defined in clause 12.2.2 of BS EN 60079-
14:2004) may also be used, provided that the peak voltage of any circuit contained within the multi-core
does not exceed 60V.
The capacitance and either the inductance or the inductance to resistance (L/R) ratio of the hazardous area
cables must not exceed the parameters specified in Table 4. The reason for this is that energy can be stored
in a cable and it is necessary to use cable in which energy stored is insufficient to ignite an explosive
atmosphere.
Group Capacitance µF Inductance mH L/R Ratio µH/ohm
IIC 0.083 4.2 55
IIB 0.65 12.6 165
IIA 2.15 33.6 440
Table 4 – Limits for Energy Stored in Cables
To calculate the total capacitance or inductance for the length of cables in the hazardous area, refer to
Table 5, which gives typical per kilometre capacitance and inductance for commonly used cables. (Note: All
Orbis IS devices have zero equivalent capacitance and inductance.)
Cable Type Core Size
mm² Conductor
resistance
ohm/km/core Inductance
mH/km Capacitance
µF/km
core to core Core to
sheath
Sheath
resistance
ohm/km
MICC Pyrotenax
light duty
2 1.5 12.1 0.534 0.19 0.21 2.77
MICC Pyrotenax
heavy duty
2 1.5 12.1 0.643 0.13 0.17 1.58
Pirelli FP200 all 1.5 12.1 0.08 0.15
PVC sheathed and
insulated to BS
6004
all 1.5 12.1 0.77 0.09
Table 5 – Examples of electrical characteristics of cables commonly used in Fire Protection Systems
DIN-rail interface enclosures
Two DIN-rail interface enclosures are available for housing intrinsically safe (IS) barriers. The enclosures
have a frosted polycarbonate lid through which LEDs can be viewed. A multi-purpose label, that features a
section for use with IS systems is supplied.
Description Item No Part No
IS DIN Rail Interface Enclosure (4 Units) 201-0142 29600-239
IS DIN Rail Interface Enclosure (10 Units) 201-0153 29600-240