How to determine the estimated power of lighting installations, the demand factor
Determination of the installed power of lighting installations
As a result of the implementation lighting calculations and the choice of lamps is determined by the installed power of the lighting load.
The installed power (rust) consists of the power of the lamps selected to illuminate the premises. When calculating lamp rust, the power of incandescent lamps (SРln), low-pressure fluorescent lamps (SRln) and high-pressure mercury arc lamps (SRlvd) must be added separately.
Determination of the estimated power of lighting installations, demand factor
To obtain the calculated power, a demand factor correction (Ks) is introduced to the installed power, because depending on the nature of the production and the purpose of the premises, some of the lamps may not be switched on for various reasons.
The expected load for incandescent lamps is determined by multiplying the installed wattage of the lamp by the demand factor:
Rrln = Rln × Ks
In lighting installations with gas-discharge lamps, when determining the design power, it is necessary to take into account the demand factor and power loss in the control device (PRA): for low-pressure fluorescent lamps:
Rr ll = (1.08 … 1.3) Rl Ks
The lower value of 1.08 is accepted for lamps with electronic ballasts; 1.2 — with starter switching circuits; 1.3 — in fast ignition circuits with a filament transformer;
Approximate power for arc mercury lamps DRL, DRI:
Rr rlvd = 1.1 Rrlvd Ks.
Work demand factor and emergency lighting
A value of the demand factor for a network of working lighting of industrial buildings is assumed:
1.0 — for small industrial buildings;
0.95 — for buildings consisting of separate large sections;
0.85 — for buildings consisting of small separate rooms;
0.8 — for administrative, comfortable and laboratory buildings of industrial enterprises;
0.6 — for warehouse buildings consisting of many separate premises.
The demand factor for calculating the lighting network for emergency and evacuation lighting is 1.0.
Determination of the estimated load when powering the lighting network from step-down transformers
The expected load from step-down transformers with a secondary voltage of 12, 24, 36, 42 V consists of permanently installed lighting devices and portable lighting loads based on the power of one hand-held lighting device 40 W with a demand factor of 0.5 ... 1.0 , taken depending on the degree of use of portable lighting.
Depending on the load, single-phase step-down transformers OSOV-0.25 are used; OSO-0.25; monophasic complete YATP-0.25; AMO-3-50 and three-phase TSZ-1.5 / 1; TSZ-2.5 / 1.