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European Safety Systems Ltd.
Impress House, Mansell Road, Acton, London W3 7QH www.e2s.com Tel: +44 (0)20 8743 8880
Document No. D251-00-601-IS Issue 1 20-09-2022 Sheet 4 of 7
Safe Area
Hazardous Area
Sounder
Terminals
IS-mC1
Combined Unit
-
+
0V
+
Power
Supply
Diode Return
Barrier
Barrier
On/Off
28V 93mA
Positive
Fig 5 Sounder single stage alarm using two channel barrier.
6.2 Sounder multi-stage alarm
Connecting terminal S2 to 0V activates the second stage
alarm, and similarly terminal S3 for the third stage alarm. Fig
6 shows how the diode return barriers may be used. If only
two stages of alarm are required the third stage barrier
should be omitted, the 28V 93mA barrier and the single diode
return channel may then be contained in one package.
S3
S2
IS-mC1
Combined Unit
Sounder
Terminals
-
+
0V
+
Power
Supply
Diode Return
Barrier
Diode Return
Barrier
Barrier
3rd Stage
2nd Stage
On/Off
28V 93mA
Positive
Hazardous Area
Safe Area
Fig 6 Sounder multi stage alarm using Zener barriers.
6.3 Beacon operation
The beacon can be operated from the same Zener barrier
being used to power the sounder (see Fig 7) or from a
separate barrier if the sounder and beacon need to operate
independently (see Fig 8). A Diode return barrier can be used
if the sounder second and third stage tones are required.
NOTE: If the beacon is operated from the same barrier as the
sounder then the sounder and beacon boards must be
connected together as shown in Fig 7 using connecting wires
that have a minimum radial thickness of insulation of 0.5mm.
Also the barrier used must meet the requirements for the
sounder section (see section 4.3).
Hazardous Area
IS-mC1
Beacon
-
+
IS-mC1
Sounder
+
-
-
+
0V
+
Power
Supply
Safe Area
Barrier
On/Off
28V 93mA
Positive
Fig 7 Combined Unit wired for simultaneous operation using
one Zener barrier.
Sounder
Power
Supply
+
0V
Barrier
On/Off
IS-mC1
Sounder
+
-
28V 93mA
Positive
Hazardous Area
Safe Area
IS-mC1
Beacon
+
On/Off
Barrier
Beacon
Power
Supply
0V
+
-
28V 1.2W
Positive
Fig 8 Combined Unit wired for independent operation using
separate Zener barriers.
7)
Electrical System Design For Installation In
Hazardous Areas Using Galvanic Isolators
Galvanic isolators do not require a high integrity earth
connection. For small systems where a high integrity earth is
not already available, the use of galvanic isolators often
reduces the overall installation cost and simplifies design.
7.1 Sounder single stage alarm
The IS-mC1 minialert combined unit may be powered by any
galvanic isolator having output parameters within the limits
specified in section 4.3, which has been certified Ex ia by an
EC Notified Body. The combined unit may be controlled by
turning the galvanic isolator on and off, or by a mechanically
activated switch on the hazardous area side of the isolator.
Safe Area
Hazardous Area
IS-mC1
Sounder
+
-
-
+
Galvanic
Isolator
Power
Fig 9 Sounder single stage alarm using galvanic isolator.
6.2 Beacon operation
The beacon can be operated from the same isolator being
used to power the sounder (see Fig 10) or from a separate
isolator if the sounder and beacon need to operate
independently (see Fig 11).
NOTE: If the beacon is operated from the same isolator as
the sounder then the sounder and beacon boards must be
connected together as shown in Fig 11 using connecting
wires that have a minimum radial thickness of insulation of
0.5mm. Also the isolator used must meet the requirements
for the sounder section (see section 4.3).
