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NISM/STPA/02
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7
ST-P-AS
ANALOGUE-ADDRESSABLE
PHOTOELECTRIC SMOKE SENSOR
INSTRUCTION MANUAL
MARCH 2001
Section 2 - ST-P-AS OPERATION
The ST-P-AS utilises the light scatter sensing
principle, using an LED and photodiode in a light proof
chamber. The LED pulses infrared light into the
smoke chamber, the photodiode being positioned
such that a minimum of light is normally received. As
the smoke enters the sensor the amount of scattered
light increases. This change is detected by the
photodiode and is amplified before being processed
and transmitted to the control panel
Section 3 - SENSOR MODELS
The ST-P-AS photoelectric smoke sensor is supplied,
as standard, with three terminals.
The ST-P-AS has the facility to activate a remote LED
indicator or auxiliary function, as standard.
The terminals on the ST-P-AS sensor head are
configured as follows:-
Terminal 3 = -VE 3 mA aux output
Terminal 1 = Sig + (+VE) positive in/out
Terminal 6 = S- (-VE) negative in/out
Section 4 - BASE MODELS
STB-4 Base:
having 4 terminals, for standard
use with ST-P-AS sensor including the auxiliary
output function.
Section 5 - INSTALLATION
In normal use, the ST-P-AS sensor will be installed at
ceiling level. Pass the field wiring through the cable
hole in the centre and from the rear of the base. Offer
up and affix the base to the ceiling or conduit fitting
with screws via the base mounting holes. Consider
visibility and orientation of the sensor's integral alarm
LED indicator when mounting the base. Connect the
field wiring to the base terminals, as detailed on page
6 making sure the wiring does not obstruct fitting of
the detector head. Fit the sensor head by inserting it
into the base and turning clockwise until the notch in
the detector rim aligns with base locking screw.
Fit the plastic dust cover supplied over the sensor to
keep out dust etc, until the system is commissioned.
If the dust cover is not fitted and the environment is
slightly dusty, such as when building work is being
completed, for example, problems of false alarms are
likely to occur after commissioning unless cleaning of
the sensor is undertaken. At commissioning, the dust
cover should be removed and discarded.
NOTE: THE PLASTIC DUST COVER MUST BE
REMOVED FROM THE SENSOR IN ORDER FOR
THE SENSOR TO FUNCTION CORRECTLY.
Section 6 - MAINTENANCE AND
CLEANING
Maintenance:
The ST-P-AS sensor is a high quality product engi-
neered for reliability. In order to obtain optimum per-
formance, periodic maintenance is required as a dirty
detector is more likely to cause a false alarm.
Servicing:
Servicing of the system should be carried out in accord-
ance with the requirements of BS 5839 Part 1, Fire
Detection and Alarm Systems for Buildings: Code of
Practice for System Design, Installation and Servicing.
The maintenance procedures described below should be
conducted with the following frequency:
One month after installation:-
Routine Inspection
and every 3 months
after.
Every 6 months:-
Operational Test
Every 12 months:-
Functional Test and
Clean
All above frequencies of maintenance are dependent on
ambient conditions.
Routine Inspection
i)
Ensure the sensor head is secure and undamaged.
ii)
Check the smoke entry apertures are in no way
obstructed.
iii)
Ensure the surface of the sensor’s outer cover is
clean. If there are deposits due to the presence of oil
vapour, dust etc, then the sensor should be cleaned in
accordance with the cleaning instructions detailed later
in this manual. It may be advisable to ensure that such
cleaning is conducted regularly in the future.
iv)
Ensure no equipment which may generate combus-
tion products or fine airborne particles, has been in-
stalled in the vicinity of the detector since the last
routine inspection. If such equipment has been in-
stalled, then you should notify the Fire Safety Officer or
other competent authority that it’s presence may
cause false alarms.
Operational Test
The purpose of the Operational Test is to confirm the
sensor’s correct operation in response to a smoke
condition.
i)
Take any necessary precautions at the control panel
to limit the sounding of the alarm sounders/bells and
any fire service summoning device.
