_______________________________________________________________________________________________________________________________
European Safety Systems Ltd.
Impress House, Mansell Road, Acton, London W3 7QH [email protected] Tel: +44 (0)20 8743 8880
www.e2s.com Fax: +44 (0)20 8740 4200
Document No. IS 4501 Issue E 27-11-09
Sheet 5 of 6
7)
Electrical System Design For Installation In
Hazardous Areas Using Galvanic Isolators
Galvanic isolators although more expensive than Zener
barriers, 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 Single stage alarm
The IS-A105N sounder 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 sounder 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.
+
IS-A105N
Sounder
+
-
Hazardous Area
Safe Area
-
Power
Galvanic
Isolator
Fig 6 Single stage alarm using galvanic isolator.
7.2 Multi stage alarm
The IS-A105N sounder second and third stages may be
activated by using Galvanically Isolated Relays that have
output parameters within the limits specified in section 4.4.
which have been certified Ex ia by an EC Notified Body.
Safe Area
Hazardous Area
-
S2
IS-A105N
Sounder
+
-
Galvanic Isolated Relay
-
Galvanic Isolator
+
Power
Power
Fig 7 Multi stage alarm using galvanic isolated relays
8)
Cable Parameters
The maximum permitted cable parameters are as specified
on the certificate of the Zener barrier or galvanic isolator that
has been selected for the installation. Normally the limits are
not restrictive, but care should be taken not to exceed a
capacitive limit of 83nF for installations when very long cables
are used.
9)
Volume Control
The output level of the IS-A105N sounder can be set by
adjusting the volume control potentiometer (see Fig 2).
10)
Servicing
No attempt should be made to repair a faulty IS-A105N
sounder. Suspect sounders should be returned to European
Safety Systems Ltd. for repair.
11)
Guarantee
Sounders that fail within the guarantee period should be
returned to European safety Systems Ltd. It is helpful if a
brief description of the fault symptoms is provided.
12)
Customer Comments
European Safety Systems Ltd. is always pleased to receive
comments from customers about our products and services.
All communications are acknowledged and whenever
possible, suggestions are implemented.
