FIRERAY 50/100
9
onds), the de tec tor will still op er ate cor rectly in di cat ing Alarm con di tions as
nor mal. Re align ment of the beam may be nec es sary if AGC fault oc curs.
3. De tec tor Po si tio ning.
It is im por tant that the De tec tor is po si tio ned cor rectly to mi ni mi se the de tec -
tion time.
Ex per i ments have shown that smoke from a fire does not rise di rectly up -
wards, but fans out or mush rooms due to air cur rents and heat lay er ing ef -
fects. The time to sig nal a fire con di tion de pends on the lo ca tion of the
De tec tor within the pre mises, the vol ume and den sity of smoke pro duced,
con struc tion of the roof, ven ti la tion ar range ments and air flow within the de -
tec tion area.
Smoke lay er ing, where smoke does not reach the ceil ing level due to lay ers
of static hot air, is over come by mount ing the De tec tor/Prism(s) at the rec -
om mended height be low the ceil ing (see sec tion 1). This brings the in fra red
beam be low the heat layer and into the smoke layer.
How ever, if there are ob jects be low the ceil ing that could ob scure the beam
pat, the de tec tor/prism(s) po si tion ing may need to be ad justed.
!
It is rec om mended that a beam path clear ance ra dius of 0.5 metres
be em ployed.
Re fer to the De tec tor mi ni mum spa cing graph on pages 9 and 10 for de tec -
tion un der flat ce i lings.
3.1. De tec tor Po si tio ning Under Flat Ce i lings.
Re fer to Fig. 1, Fig. 2.
+
In all in stal la tions the lat est Na tional Fire Stan dards
must
be con sulted.
If there is any doubt on the cor rect mount ing height, po si tion ing may be
ter mi nated by smoke tests.
3.2. De tec tor Po si tio ning In Apex Of Slo ping Ce i ling.
A ce i ling is de fi ned as slo ping if the di stan ce from the top of the apex to the
in ter sec tion of the ce i ling and ad ja cent wall is gre a ter than 0.6 me tres. See
Fig. 3.
When a De tec tor is po si tioned in the apex of a ceil ing (See Fig.4), the lat eral
beam dis tance cov ered (Y) can be in creased in re la tion to the an gle of the
pitch (
Φ
), to a max i mum pitch of 25º.
For Ex am ple:
If the pitch an gle is 20 de grees, the lat eral cov er age can be in creased from
7.5 metres ei ther side of the beam (Y) to:
Y = 7.5 + (7.5 x 20/100) metres
Y = 9 metres
1. Sys tem De scrip tion
The De tec tor com pri ses a Tran smit ter and Re ce i ver con ta i ned wit hin one
enclosure.
The Trans mit ter emits an in vis i ble in fra red light beam that is re flected via a
prism(s) mounted di rectly op po site and with a clear line of sight. The re -
flected in fra red light is de tected by the Re ceiver and ana lysed.
The De tec tor has a ma xi mum la te ral de tec tion de fi ned by the lo cal Na tio nal
Stan dard. As a gui de a com mon la te ral di stan ce of 7.5m will be used in this
gui de. Use the la test beam de tec tor stan dards EN54 part 12, VdS2095 or
BS5839 part 1 for fur ther gui dan ce.
The op ti mal beam di stan ce from the ce i ling will be bet we en 500mm and
600mm, aga in the Lo cal Na tio nal Stan dard will give gui dan ce.
2. System Ope ra tion.
Smo ke in the beam path will re du ce the re ce i ved in fra red light pro por tio nally
to the den sity of the smoke. The De tec tor anal y ses this at te nua tion, or
obscuration of light, and acts ac cord ingly.
Alarm thresh olds of 25% , 35% , and 50% can be se lected to suit the en vi -
ron ment, where 50% is the least sen si tive. If the re ceived in fra red sig nal re -
duces to be low the se lected thresh old and is pres ent for ap prox i mately 10
sec onds, the Alarm re lay is ac ti vated, and the Alarm Led illuminates.
There are two modes to the op er a tion of the Alarm re lay. Auto re set and Alarm
Latch ing. Auto re set mode will re set the Alarm re lay,and Alarm LED, 5 sec -
onds af ter the re ceived in fra red sig nal has re cov ered to a level above the
alarm thresh old. Latch ing mode holds the Alarm re lay, and alarm LED, ac tive
in def i nitely af ter an alarm con di tion has oc curred.
There are two meth ods to clear the latched mode.
1)
Place the beam into Prism Tar get ing or Align ment Mode, and then go
back to Run Mode.
2)
Re move power to the beam. Power must be re moved from the De tec tor
for
10 sec onds.
If the in fra red beam is ob scured rap idly to a level of 93% ,or greater, for ap -
prox i mately 10 sec onds the fault re lay is ac ti vated. The Fault LED will also il lu -
mi nate. This con di tion can be en tered in a num ber of ways, for ex am ple, an
ob ject be ing placed in the beam path, trans mit ter fail ure, loss of the prism(s),
or sud den mis align ment of the De tec tor, or the re ceived sig nal be comes too
high. The fault re lay will re set within 5 sec onds of the con di tion be ing rec ti fied.
The De tec tor mon i tors long term deg ra da tion of sig nal strength caused by
com po nent age ing or build up of dirt on op ti cal sur faces. This op er ates by
com par ing the re ceived in fra red sig nal against a stan dard ev ery 15 min utes;
dif fer ences of less than 4.7% /Hour are cor rected au to mat i cally. When the
de tec tor is show ing AGC fault (Fault LED flash ing once in ev ery two sec -
Maximum
M
ax
im
u
m
M
in
im
u
m
FIG.1
Typ i cal in stal la tion ( Re fer to graph for min i mum De tec tor spac ing)
ENGLISH
