How to Read Ratio of Transverse Distance to Mounting Height
Important DEFINITIONS IN Electrical LIGHTING Pattern:
The following are some of the definitions which we come across in the design of electrical lighting scheme.
1) UTILIZATION FACTOR:
Utilization Cistron or Co-efficient of utilization. It may be defined as "the ratio of full lumens received on the working plane to the total lumens emitted by the light source".i.e.
Utilization factor =Lumens received on the working aeroplane/Lumens emitted by the lamp
Gene EFFECTING UTILIZATION Factor:
Blazon of light, light plumbing fixtures, Colour surface of walls and ceiling, mounting height of lamps, Surface area to exist illuminated
Its value lies between 0.iv and 0.6 for direct fittings it varies from 0.1 to 0.35 for indirect fittings
2)Depreciation or Maintenance gene
It may be defined as "the ratio of illumination nether normal working condition to the illumination when everything is clean or new" i.e.
D.F = Illumination under normal working atmospheric condition / Illumination when everything is clean.
The maintenance factor is based on how ofttimes the lights are cleaned and replaced. It takes into account such factors as decreased efficiency with age, accumulation of dust within the fitting itself and the depreciation of reflectance as walls and ceilings age. For convenience, it is ordinarily given every bit iii options:
Adept = 0.seventy
Medium = 0.65
Poor = 0.55
3) WASTE LIGHT Factor:
When a surface is illuminated by a number of lamps, at that place is certain amount of wastage due to overlapping of low-cal waves. Its value will exist betwixt 1.2 to one.5
4) REFLECTION FACTOR:
It may be defined equally "the ratio of luminous flux leaving the surface to the luminous flux incident on it". It's value volition be always less than 1
five) Assimilation FACTOR:
When the atmosphere is full of snow or smoke fumes, it absorbs some light. Hence assimilation factor may be defined equally "the ratio of cyberspace lumens available on the working plane after absorption to the total lumens emitted by the lamp". It'south value varies from 0.5 to ane
6)LUMINOUS EFFICIENCY OR SPECIFIC OUT PUT
It may be defined equally "the ratio of number of lumens emitted to the electric power in take of a source" it's unit is lumen/watt (lm/W)
7) SPACING TO MOUNTING Summit RATIO (SHR)
The Spacing to Mounting Pinnacle Ratio (SHR) is thespacing between luminaires divided by their height above the horizontal reference airplane.
eight) ROOM Alphabetize:
The room index is a ratio, describing how the room'due south height compares to its length and width. It is given by:
Where 50 is the length of the room, W is its width, and Hm is the mounting summit in a higher place the work plane.
LUMEN METHOD STEPS:
one. Discover required lux level
2. Select luminaire
three. Make up one's mind room index
iv. Determine Number of Fixtures
N = number of lamps required.
E = illuminance level required (lux)
A = area at working aeroplane superlative (m2)
F = average luminous flux from each lamp (lm)
UF= utilisation factor,
MF= maintenance gene,
5. Determine Minimum spacing betwixt luminaire
Minimum spacing = SHR * Hm
Hm= Mounting height
SHR= Space to height ratio.
6. Decide Number of required rows of luminaire along width of the room
Number of required rows= width of the room/ Minimum spacing
7. Decide Number of luminaire in each row
Number of luminaire in each row= Total luminaire / Number of rows
8. Axial spacing along luminaire
Axial spacing= Length of the room/ Number of luminaire in each row
9. Transverse spacing betwixt luminaire
Transverse spacing = Width of the room/ Number of luminaire in each row
EXAMPLE 1:
An office has length of 20m, width=10m,height=3m.
one) Ceiling to desk top is 2m.
2) Expanse to be illuminated to a full general is 250 lux using twin lamp 32 watt CFL Luminaire with a SHR of ane.25.
3) Each lamp has an initial output of 85 lumen per watt.
iv) Maintenance gene is 0.63, Utilisation factor is 0.69
Design a lighting system for this office
EXAMPLE 2:
The part measures 10*seven thou with a flooring to ceiling height of 3m. The working plane height is 0.8m. Office is being used for full general office duties including some estimator use. Decide number of luminaires required in this part
EXAMPLE 3:
EXAMPLE 4:
Source: https://www.linkedin.com/pulse/lighting-design-lumen-method-examples-hasan-tariq
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