14. The emergency
supply for this type installation often supplied from central battery,
the emergency lamps being wired parallel from the low-voltage supply
as shown Fig.2). wise precaution supervisory buzzer the emergency
supply prevent accidental discharge the batteries, since not oth-
erwise obvious which supply being used. 5266 and EN
1838 states that after battery discharged being called into operation
for its specified duration time, should capable once again operat-
ing for the specified duration time following recharge period not lon-
ger than 24h. Escape sign lighting units used commercial facili-
ties should wired the maintained mode.
There are two possible modes operation for emergency lighting installa-
tions: maintained and non-maintained.
The emergency lighting supply must have adequate capacity and rating
for the specified duration time (IEE Regulation 313. The duration time for which the emergency lighting should
operate will specified statutory authority but normally 1–3h.
Definition
In maintained system the emergency
lamps are continuously lit using the
normal supply when this available,
and change over alternative
supply when the mains supply fails.
. The
British Standard states that escape lighting should operate for minimum
of hour.59. The advantage this system that
the lamps are continuously proven healthy and any failure immediately
obvious. Standby lighting operation time will depend upon financial con-
siderations and the importance continuing the process activity.
MAINTAINED EMERGENCY LIGHTING
In maintained system the emergency lamps are continuously lit using
the normal supply when this available, and change over alternative
supply when the mains supply fails.
Transformer
Supply
Rectifier
Emergency
lamps
Emergency
supply
Supervisory
bell
Normally open
relay
FIGURE 14.
Maintained emergency lighting normally installed theatres, cinemas,
discotheques and places entertainment where the normal lighting may
be dimmed extinguished while the building occupied.59
Maintained emergency lighting.Basic Electrical Installation Work
340
unacceptable, and these cases battery supply required supply the
load until the generator can take over
