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
BR385 sounders may be powered by any Ex ia ATEX certified galvanic
isolator having output parameters within the limits specified in section 4.3.
The sounder may be controlled by turning the galvanic isolator on and off,
or from the hazardous area by a mechanically activated switch complying
with the requirements for simple apparatus as defined by EN 60079-11.
i.e. having IP20 protection and able to withstand a 500V rms insulation
test to earth for one minute.
Fig 7 Single stage alarm using galvanic isolator
.
7.2 Multi-stage alarm
Fig 8 shows a typical application in which the first and second stage alarm
tones are activated by the alarm outputs of a BA327E intrinsically safe
loop powered indicator. The BA327E alarm outputs have been certified as
simple apparatus and may therefore be used to switch the BR385 sounder
in the hazardous area. The contacts of most certified intrinsically safe
relays may also be used in the same way.
Fig 8 Loop-powered BA327E intrinsically safe indicator
activating BR385 first and second stage alarms
8. ACCESSORIES
8.1 Tag number
BR385 sounders can be supplied identified by a tag number thermally
printed on a self adhesive label.
9. SERVICING
No attempt should be made to repair a faulty BR385 sounder. Suspect
sounders should be returned to BEKA associates or our local agent for
repair.
10. GUARANTEE
Sounders which fail within the guarantee period should be returned to
BEKA associates or our local agent. It is helpful if a brief description of
the fault symptoms is provided.
11. CUSTOMER COMMENTS
BEKA associates is always pleased to receive comments from customers
about our products and services. All communications are acknowledged
and whenever possible, suggestions are implemented.
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