3) Installation
requirements
SPECIAL CONDITIONS FOR SAFE USE (as stated on the
EC Type Examination Certificate SIRA 04ATEX2301X)
The equipment shall only be supplied via Ter w.r.t.
Terminals – from a barrier having a maximum open circuit
voltage U
o
that is
28 V and a maximum short circuit current
I
o
that is
93 mA, where I
o
is resistively limited. The barrier
shall be ATEX certified by a notified body.
The total capacitance connected to ter wrt – (i.e. the
capacitance of the cable plus any other capacitance) shall
not exceed 83 nF.
The equipment has an ingress protection rating of IP66;
however, if it has been supplied without a cable entry device,
then the user shall ensure that the device that is fitted will
provide an ingress protection that is appropriate to the
environment in which it is installed i.e. IP20 or better.
The enclosure may be manufactured from cast aluminium. In
rare cases, ignition sources due to impact and friction sparks
could occur. This shall be considered during installation,
particularly if the equipment is installed in an area requiring
Equipment Protection Level Ga.
3.1 Ter and –
Power is supplied to the sounder via the + and – terminals
which have the following input safety parameters:
The IS-D105 sounder may be powered from an ATEX
certified Zener barrier or galvanic isolator which have output
parameters equal to or less than 28V, 93mA and 660mW
where Io is resistively limited. The cable parameters stated
on the selected Zener barrier or galvanic isolator certificate
must be observed.
Up to three IS-D105 sounders can be connected in parallel
and powered from a common barrier or isolator. Connecting
two sounders in parallel will reduce the output from each by
about 3dB. Three sounders should only be powered from a
common supply when the maximum supply voltage is
available.
3.2 Terminals S2 and S3
When terminals S2 or S3 are connected to 0V (- terminal) the
sounder output tone changes to the second or third stage
alarm respectively. The input safety parameters for these
terminals are:
Ui
=
28V
Ii
=
0mA
Because the permitted input current is zero, these terminals
may only be connected to a diode return barrier, an
intrinsically safe relay or a galvanic isolator, all of which must
have been certified by an EC Notified Body. Only diode
return barriers with a voltage drop of less than 0.9V may be
used. Alternatively, these terminals may be connected
directly to a mechanically activated switch within the
hazardous area.
Fig 1 Simplified block diagram
3.3 Description
Fig 1 shows a simplified block diagram of an IS-D105
sounder. The device operates immediately when power is
applied to the + and – terminals which are duplicated to allow
a second sounder to be connected in parallel, or for an end of
line monitoring resistor to be installed. The output tone is
defined by the positions of the six internal switches and this
tone can be changed to a second or third stage alarm tone by
connecting terminals S2 or S3 to 0V. The tone generator is
crystal controlled to ensure that when two sounders are
started at the same time the output tones remain
synchronised.
3.4 Supply Voltage
The IS-D105 sounder has been designed to operate in a
hazardous area from a 24V dc supply via 28V 93mA resistive
ATEX and IECEx certified Zener Barriers or Galvanic
Isolators. The sounders may be tested or used in safe areas
without a Zener barrier or galvanic isolator, but at supply
voltages above 16V the internal current limit will function and
therefore it is recommended that they are not operated
continuously with a direct supply greater than 16V.
Fig 2 Location of field terminals and controls.
Ui
28V
Ii
93mA
Pi
660mW
Ci
0mA
Li
0mA
Input Terminals
Volume Control
Tone Setting
Switches 1-6
Sounder
Tone
DIP Switch
