Man-1078_Sigma_CP_22
Page 8 of 24
3B
4. Using intrinsically safe barriers
SIGMA CP control panels support the use of I.S. barriers for connecting to equipment in hazardous areas.
Only certified detectors, call points and sounders may be used in hazardous areas and these
must be connected to the control panel via a compatible I.S. barrier as listed in table 7.
Connection of the I.S. barrier changes the characteristics of the detection circuit so zones that have I.S.
barriers connected must be adjusted to work with them.
Programmable options C61 to C68 allow each zone to operate with I.S. barriers.
The amount of detectors and call points that can be connected to a zone is limited by the I.S. approval
system diagram which should be supplied by the detector manufacturer. The power rating of the end of line
resistor will be dependent upon the Zone classification rating (Gas class) this will be specified on the system
diagram.
Figure 1. Detection zone wiring through an
MTL5561
I.S .barrier
+
-
S
O
U
N
D
E
R
O
U
T
P
U
T
I.S .
POLARISED
SOUNDER
10K END OF LINE RESISTOR
MTL7778ac
MAXIMUM OF TWO SOUNDERS PER SOUNDER CIRCUIT
I.S .
EARTH
POWER WILL DEPEND UPON
I.S. ZONE CLASSIFICATION
HAZARDOUS AREA
SAFE AREA
+
IN
+
OUT
-
IN
-
OUT
I.S .
POLARISED
SOUNDER
+
IN
+
OUT
-
IN
-
OUT
Figure 2. Sounder circuit wiring through an MTL7778ac I.S. barrier
+
-
Z
O
N
E
+
IN
+
OUT
-
IN
-
OUT
I.S. DETECTOR
I.S . CALL POINT
MTL5561
6K8 END OF
LINE RESISTOR
+
-
+
-
SAFE AREA
HAZARDOUS AREA
POWER RATING WILL
DEPEND UPON I.S. ZONE
CLASSIFICATION
NOTE: Active End of
Line Devices (LCMU)
must not be used in
the Hazardous Area
MAXIMUM NUMBER OF DEVICES ON ZONE
SPECIFIED IN SYSTEM DIAGRAM
Summary of Contents for Sigma CP K Series
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