Technical information

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The total energy consumed for lighting is
calculated according to the formula and is stated
kWh/year:
W
total
=W
light
+ W
parasitic
W
light
is the estimated energy consumption used to power the
lighting in the building during a given period. All light
sources and ballasts included.
W
parasitic
is the estimated energy used when the lighting is extin-
guished. That is to say, the energy used by the ballast in
standby mode or for charging emergency luminaires.
W
light
is aected by the following factors
P
n
is the total installed lighting output within a room or zone, measured in watts
(P
n
=∑P
i
).
F
C
is a correction factor for constant illuminance in a room or a zone.
F
C
is aected by:
Maintenance factor (β).•
Maintenance plan. •
When constant light control is used:
F
C
=(1+maintenance factor)/2, otherwise the standard value 0.9 is used.
F
D
is a correction factor for daylight. F
D
relates use of the total lighting output to
the availability of daylight in the building.
.
F
D
is aected by:
The daylight factor (amount of daylight).•
Illuminance.•
Type of control.•
F
O
is a correction factor depending on presence. F
O
relates use of the total lighting
output to the presence time in the building.
F
O
is aected by:
Presence/absence.•
The type of control.•
Total utilisation time (t tot) day+night (t•
N
+t
D
).
The formula to calculate the energy consumption:
W
light
= [∑(P
n
xF
C
) x [(t
D
x F
D
x F
O
) + (t
N
x F
O
)]] / 1000 (kWh/year)
P
em
charging power for emergency
lightingwithin the building.
t
em
is the charging time for emergency
lighting (standard value for t
em
is
8760 h/year).
Emergency lighting system
Control system
P
light-o
parasitic “standby” power for
control equipment when the
lighting is in the “o position”.
t
light-o
when the lighting is in the
“o position” [t
Y
– (t
D
+ t
N
)]
(standard value for t
Y
is
8760 h/year).
W
parasitic
is aected by the following factors
The formula to calculate the parasitic energy:
W
parasitic
=[∑P
pc, Light-o
x t
Light-o
+ (P
em
x t
em
)] / 1000 (kWh/year)
Which factors aect the lighting’s output in op-
eration, W
light
?
Which factors aect the lighting’s output when
it is extinguished, W
parasitic
?
Energy directive 2002/91/EC
To calculate energy usage for lighting (W
total
) according to EN 15193
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