Lighting & power design citam

Edson Engineers Page 1
EDSON ENGINEERS.
DESIGN CALCULATIONS.
LIGHTING AND POWER DESIGN CALCULATIONS.
BY
FRED BUTETE WAMBASI.
PROJECT: CITAM KAREN BOYS AND GIRLS TOILETS
JANUARY 2015
Power
Design
Calculations
Lighting

1.0 Lighting Design.
1.1 Formulae and Fundamental Considerations.
Lighting design aims at determining the number of lighting fixtures (luminaries)
required in order to achieve the recommended illumination for a given task.
Key considerations prior to design are;
 The dimensions of the room; Length, Width and mounting height of the
luminaire from working plane.
 The nature of ceiling, walls, and floors in terms of coluor and material.
 The functionally/use of the design area to be illuminated.
 Non analytical factors affecting the choice of luminaires, aesthetics and
natural lighting.
In determining the number of lighting fixtures (luminaries) required, key among
other factors; the following has to be established:
 Recommended illuminance (Lux) in Lumens/m²
 Utilization factor
 Maintenance factor of the Luminaire
 Nominal lamp Luminous flux/output in Lumens.
Quantity of light here is specified by illuminance which is measured in lux (lm/m2
of illuminated surface).
The Lumen method formula used is as below (as per CIBSE Lighting guide and a
textbook on building services engineering by David V. Chadderton: Building Services Engineering
Fifth edition (2007) - Taylor and Francis Group - New York ).

=
Øn xn xMf xUf
Where:
E = Average recommended illuminance (Lux) in Lumens/m²
A = Area of the working plane (m²)
Øn= Nominal Lamp Luminous Flux
Mf = Maintenance factor
Uf = Utilization factor
N= Number of Luminaires
n= No. of luminaire’s lamps
1.2 Definitions:
a. Utilization factor (Uf)
This represents the proportion of luminous flux of the lamp that reaches the
working plane and is dependent on the following:
 Luminaire efficiency
 Lighting fitting distribution
 Reflectances of the room surfaces i.e. ( Ceiling, walls and floor)
 Room index.
The room index represents the geometrical ratio of the area of the
horizontal surfaces to that of the Vertical surfaces measured from the
working plane in the room and is expressed as:
Ri =
(L x W)
( + )
Where:
L = Length of the room

W = Width of the room
Hm = Height of the Luminaire above the working plane.
The room reflectances depend on the room surface finishes. In my design
the ceiling is painted white, floor is terrazzo/pvc tiles in some areas and the
walls are painted white.The design reflectance ratio used is C: W: F = 0.7:
0.5: 0.2. Hm of 2.05m is used herein in design calculations.
Standard photometric tables for a combination of various values of room
indices and surface reflectances exist (given by manufacturers) from
which the value of the utilization factor (Uf) was directly obtained or
extrapolated for values of Room indices that were not integers as follows:
= ( ) + ( − ( )
( ) − ( )
( ) − ( )
where: (U= upper Value& L= Lower Value)
b. Maintenance factor (Mf)
This gives the proportion of illuminance provided by a luminaire in normal
working conditions (dirty conditions) of both the luminaire and the room
surfaces to the illuminance of the same luminaire in clean conditions.
For this design, I used a maintenance factor of 0.8 on the assumption that
the room surfaces will be maintained very clean most of the times given
this is children’s toilet where high standards of cleanliness are desired.
c. Nominal Lamp Luminous Flux (Øn)
The value was obtained from lamp photometric data usually provided by
manufacturers in the catalogues.
d. Illumination level (E)
These were read from a chart guide used for obtaining recommended
illuminance (Lux) prepared by the Chartered Institute of Building Services

Engineers (CIBSE) and the Philips Lighting design Manual. These values
entirely depend on the type of use the room is put into. The illuminance are
as summarized in the tables below:
The following are the recommended Illumination Levels;
a) Hospital
Item Description Recommended
Lux (E) in
Lumens/M2
1.0 Corridors: Night
Daytime/ Evening
50
200
2.0 Wards: Circulation at night
Observation at night
General Lighting
Simple Examination/Reading
30
5
150
300
3.0 Examination Rooms: General Lighting
Local Examination
Lighting
500
1000
4.0 Intensive therapy: Bedhead
Observation
50
750
5.0 Nurses Stations 300
6.0 Operating Theaters: Pre-Op room
General theater lighting
-
500
1000
-
7.0 Laboratories & Pharmacies: General Lighting
Local
750
1000
8.0 Consulting Rooms: General Lighting
Local
500
750
9.0 Autopsy Rooms: General Lighting
Local
750
5000

b) Offices
Lux E in Lumens/M2
1.0 General offices with typing, computers e.t.c 500
2.0 Conference rooms 300
3.0 Archives 200
c) General Building areas
Lux E in Lumens/M2
1.0 Circulation areas, corridors 100
2.0 Cloak rooms, toilets 100
3.0 Stores, Stock rooms 100
4.0 Stairs, escalators 150
d) Kitchen Block
Lux E in Lumens/M2
1.0 Servery 300
2.0 Kitchen 500
3.0 Food stores 150
4.0 Food preparation area 500
5.0 Cold store 300
6.0 Office 500
7.0 Kitchen yard 30

e) Laundry Block
Lux E in Lumens/M2
1.0 Pressing 500
2.0 Sewing/Mending 750
3.0 Gents/Ladies 100
f) Workshop Block
Lux E in Lumens/M2
1.0 Welding 300
2.0 Machine work, coil winding 500
3.0 Fine bench & Machine work 750
4.0 Testing/ adjusting Electrical components 1000
2.0 Lighting Design Task.
2.1 Boys Toilets.
2.1.1 Area Outside toilets having whbs within toilet block.
The room dimensions are:
Length of the room, L = 8.9m
Width of the room, W = 5.8m

For this toilets, the design illuminance E = 100 Lux as the lighting requirements are
for cloak rooms and toilets. The luminaire chosen was 1200mm 1x36W
ELECTRONIC BALLAST single batten fluorescent fitting with acrylic diffuser as
pierlite. For this fitting, the nominal luminous flux Øn = 5400 lumens per lamp.
Height of the luminaire above the working plane Hm = 2.05m
Therefore the room index Ri = L x W
Hm (L + W)
= 8.9 x 5.8 = 1.40
2.05(8.9+5.8)
From the photometric tables, and by extrapolation, the utilization factor is
obtained as
= ( ) + ( − ( )
( ) − ( )
( ) − ( )
= 59 + (1.40 − 1.25) . .
=62.09% = 0.6209
The number of luminaires is given as,
=
100 51.62
3450 x1 x0.8 x0.6209
= 3.0122

Thus we use 3 No.Luminaires,1200mm 1x36W Electronic Ballast single
batten fluorescent fitting with acrylic diffuser as pierlite to provide lighting for the
area.
This gives an illuminance of :
=
Øn xn xMf xUfxN
A
=
3450 x1 x0.8 x0.6209x3
51.62
= 99.59
Thislevel of illumination is acceptable as the luminaires will therefore provide
adequate lighting for the area required.
2.1.2 Area inside toilets having wcs but within toilet block.
for cloak rooms and toilets. The luminaire chosen was 16W Polo Opal C/W lamp
downlighter with
white lining. For this fitting, the nominal luminous flux Øn = 1250 lumens per lamp.

Hm (L + W)
= 4.5 x 2.0 = 0.555351682
2.05(4.5+2.0)
obtained as
= ( ) + ( − ( )
( ) − ( )
( ) − ( )
= 48 + (0.56 − 0.75) . .
=44.10% = 0.441
=
100 9.08
1250 x1 x0.8 x0.441
= 2.058
Thus we use 2 No.Luminaires, as 16W Polo Opal C/W lamp downlighter with
White lining to provide lighting for the area.
. This gives an illuminance of:
=
Øn xn xMf xUfxN
A

=
1250 x1 x0.8 x0.441x2
9.08
= 97.14
2.1.3 Paraplegic toilets.
downlighter with
Hm (L + W)
= 2.38 x 1.5 = 0.448830
2.05(2.38+1.5)
obtained as
= ( ) + ( − ( )
( ) − ( )
( ) − ( )

= 48 + (0.449 − 0.75) . .
=41.98% = 0.42
=
100 3.57
1250 x1 x0.8 x0.42
= 0.85
=
Øn xn xMf xUfxN
A
=
1250 x1 x0.8 x0.42x1
3.57
= 117.64
This level of illumination is acceptable (within + 30%) as the luminaires will
therefore provide adequate lighting for the area required.
2.1.4 Showers.

downlighter with
Hm (L + W)
= 2.0 x 1.5 = 0.418
2.05(2.0+1.5)
obtained as
= ( ) + ( − ( )
( ) − ( )
( ) − ( )
= 48 + (0.418 − 0.75) . .
=41.36% = 0.41
=
100 3.0
1250 x1 x0.8 x0.41
= 0.73

This gives an illuminance of:
=
Øn xn xMf xUfxN
A
=
1250 x1 x0.8 x0.41x1
3.57
= 114.85
This level of illumination is acceptable (within + 30%) as the luminaires will
therefore provide adequate lighting for the area required.
2.1.5 Area in front of cleaners’ room (corridor space).
For this toilets, the design illuminance E = 150 Lux as the lighting requirements for
this space. The luminaire chosen was 16W Polo Opal C/W lamp downlighter
with white lining. For this fitting, the nominal luminous flux Øn = 1250 lumens per
lamp.
Hm (L + W)
= 2.23 x 2.17 = 0.536
2.05(2.23+2.17)

obtained as
Uf = 48 + (0.536 − 0.75) . .
=43.72% = 0.44
=
150 3.0
1250 x1 x0.8 x0.44
= 1.023
=
Øn xn xMf xUfxN
A
=
1250 x1 x0.8 x0.44x1
3.0
= 146.67
This level of illumination is acceptable as the luminaires will therefore provide
adequate lighting for the area required.Being a room that is not used all day
illumination levels are however not as significant as in other areas of the block.

2.2 Girls Toilets.
2.2.1 Area Outside toilets having whbs within toilet block.
Width of the room, W = 4.02
for cloak rooms and toilets. The luminaire chosen was 1200mm 1x36W
ELECTRONIC BALLAST single
batten fluorescent fitting with acrylic diffuser as pierlite. For this fitting, the
nominal luminous flux Øn = 5400 lumens per lamp.
Hm (L + W)
= 11.9 x 4.02 = 1.47
2.05(11.9+4.02)
obtained as
= ( ) + ( − ( )
( ) − ( )
( ) − ( )

= 59 + (1.47 − 1.25) . .
=63.4% = 0.634
=
100 47.84
3450 x1 x0.8 x0.634
= 2.73
Thus we use 3 No.Luminaires, 1200mm 1x36W Electronic Ballast single
batten fluorescent fitting with acrylic diffuser as pierlite. to provide lighting for
the area.
This gives an illuminance of :
=
Øn xn xMf xUfxN
A
=
3450 x1 x0.8 x0.634x3
47.84
= 109.73
2.2.2 Area inside toilets having wcs but within toilet block.

downlighter with
Hm (L + W)
= 10.215 x 2.0 = 0.816
2.05(10.215+2.0)
obtained as
= ( ) + ( − ( )
( ) − ( )
( ) − ( )
= 48 + (0.816 − 0.75) . .
=49.32% = 0.4932
=
100 20.43
1250 x1 x0.8 x0.4932
= 4.142

=
Øn xn xMf xUfxN
A
=
1250 x1 x0.8 x0.49x4
20.43
= 95.94
2.2.3 Paraplegic toilets.
downlighter with white lining. For this fitting, the nominal luminous flux Øn = 1250
lumens per lamp.
Hm (L + W)
= 2.0 x 1.5 = 0.585
2.05(2.0+1.5)

obtained as
= ( ) + ( − ( )
( ) − ( )
( ) − ( )
= 48 + (0.585 − 0.75) . .
=44.7%=0.447
=
100 3.0
1250 x1 x0.8 x0.447
= 0.67
=
Øn xn xMf xUfxN
A
=
1250 x1 x0.8 x0.447x1
3.0
= 149

3.0 Power Design.
3.1 Formulae and Fundamental Considerations.
The following formulae as provided in the IEE Wiring regulations 17th Edition (BS
7671:2008) and its guide: Design and Verification of Electrical Installations by
Brian Scaddan( IEng, MIET) – Newnes Publishers UK (2008) were used in
calculations pertaining to power.
3.1.1 Design current I b
This is defined as ‘the magnitude of the current to be carried by a circuit in
normal service ’ , and is either determined directly from manufacturers’ details
or calculated using the following formulae as provided by 17th Edition of IEE
wiring regulations :
3.1.1 (a) Single phase loads.
= or =
3.1.1 (b) Three phase load
=
√
or =
√ %
In both cases where:
P _ power in watts
V _ line to neutral voltage in volts
V L _ line to line voltage in volts
Eff% _ efficiency
PF _ power factor.

3.1.2 Diversity
The application of diversity to an installation permits, by assuming that not all loads
will be energized at the same time, thus a reduction in main or distribution circuit
cable sizes. The IEE Regulations Guidance Notes or On-Site Guide tabulate diversity in
the form of percentages of full load for various circuits in a range of installations.
However, it is for the designer to make a careful judgement as to the exact level of
diversity to be applied by consideration of the actual design intended, most a times
designer judgement is employeds .
3.1.3 Nominal rating or setting of protection In.
In is that it should be greater than or equal to I b. We can select for this condition
from IEE Regulations Tables 41.2, 41.3 or 41.4. For types and sizes outside the scope of
these tables, details from the manufacturer will need to be sought.
3.1.4 Selection of suitable conductor size .
Based on the quantity of current anticipated. This is obtainable from calculations and
reference to standard cable rating tables.
3.1.5 Sizing the protective device
According to IEE regulations:
Ib≤ II ≤ Ic
Where:
Ib= Design current of the circuit
II = Nominal current or current setting of the protective device
Ic = Current carrying capacity of the conductor in the particular installation
conditions
3.1.6 Voltage drop
In many instances this may well be the most onerous condition to affect cable sizes.
The Regulations require that the voltage at the terminals of fixed equipment should
be greater than the lower limit permitted by the British Standard for that equipment,

or in the absence of a British Standard, that the safe functioning of the equipment
should not be impaired. These requirements are fulfilled if the voltage drop between
the origin of the installation and any load point does not exceed the following values
(IEE Regulations, Appendix 12) ( Table 3.1 Below ). Standard cable current ratings are
tabulated against voltage drop in milli-volts (mV) dropped for every ampere of
design current (A), for every metre of conductor length(m), case of Tables 9D1, 9D2,
9D3, 9E1 etc in BS Code i.e.
Volt drop = mV/A/m (IEE 17th Edition)
Table 3.1
Lighting Power
3% 5%
240V Single phase 7.2V 12V
415V three phase 12.5V 20.8V
or fully translated with Ib for A and L (length in metres) as below formulae:
Formulae.
= volts = Vd = I x ∂ x L Volts (IEE 17th Edition)
3.2 Power Calculations for Both toilet Blocks.
3.2.1 Fixed power loads on distribution boards calculations, power supply cable and
protective switch gear sizing.
The ratings of the cable size and protective switch gear at the distribution board for
individual equipment /appliance is established from its load current during starting
operation voltage drops are pertinent in proper cable sizing and safety of operation.

3.2.1( a ) Calculations.
The loads are single phase and thus single phase distribution supply adopted for
economic justification.
Formulae for calculation is provided above (also indicated below) as per IEE Wiring
standards .
=
( )
or =
( )
3.2.1(b) Hand drier spur point Cable Sizing and Circuit breaker rating.
Consideration during design is made for each spur point.This is performed assuming
the hand drier is in full operation. Ideal Load due to hand drier is used, Assuming
diversity of 1.
= =
3000
240 0.8
= 15.63
From IEE Wiring Regulations tables, a cable of 2.5mm2 SC PVC insulated copper
cables is sufficient for the operation, however considering the overshoot during start
operation 4.0 mm2 SC Insulated by PVC copper cables can be used to cater for the
in currents rush as the case of a childrens’ toilet and also considering that the
distance from the DB to the spur point is very short, thus negligible economic
implications. (BS 6004 , BS 6346)
Thus a 20 A Double pole switch is chosen for the hand drier.
A protective circuit breaker of 20 A TP MCB is chosen for hand drier circuit.

3.2.2 Current to CU’s, Cable Sizing for Armoured Cable and Choice of MCCB.
3.2.2(a) CU – CA , Girls toilets.
Total load on CU – CA in Kw is given in the table below.
ITEM NO RATING Total
Wattage(KW)
Total
Wattage x
1.8
Total
Wattage
for
Fluorescent
(Watts)
Fittings
Diversity Applying a
Diversity
(KW)
Flourescent
Lights
3 0.036 0.108 0.194 0.9 0.175
Security
Lights
4 0.060 0.240 - 0.5 0.120
Down
Lights
5 0.016 0.080 - 0.9 0.072
Double
Poles
1 3.0 3.000 - 0.7 2.100
TOTAL KW 2.467
ASSUMING PF = 0.8 KVA 1.974
Table3.2
Total load supplied to CU – CA was 2.467 Kw.
Allowing for 10% Extra Load for future additional load.
2.467Kw + 10/100*2.467Kw = 2.714 Kw
Design Load Current =
.
= 14.14 A
The maximum allowed voltage drop is 5% of 240 V0lts = 12V
= volts = Vd = I x ∂ x L Volts
Since the CU’s are approximately 45 m from Maintenance workshop,
Maximum value of ∂ = Vd /( Ib x L) Volts = 12 / (14.14 x 45) = 18.86 Mv/A/m ,thus a

Armorued cable of 4mm2 with a voltage drop of 12 Mv/A/m is chosen. Giving a total
voltage drop of:
Vd = 14.14 x 12 x 45 x 10-3 Volts = 7.64 Volts.
The MCCB chosen is 20 A.
Since ; Ib≤ II ≤ Ic
Where:
conditions
Ib = 14.14 A, II = 20 A Ic = 37 A.
3.2.2(b) CU – CB , Boys toilets.
Total load on CU – CA in Kw is given in the table below.
ITEM NO RATING Total
Wattage(KW)
Total
Wattage x
1.8
Total
Wattage
for
Fluorescent
(Watts)
Fittings
Diversity Applying a
Diversity
(KW)
Flourescent
Lights
3 0.036 0.108 0.194 0.9 0.175
Security
Lights
5 0.060 0.300 - 0.5 0.150
Down
Lights
6 0.016 0.096 - 0.9 0.086
Double
Poles
1 3.0 3.000 - 0.7 2.100
TOTAL KW 2.511
ASSUMING PF = 0.8 KVA 2.009
Table3.3
Total load supplied to CU – Cb was 2.511 Kw.
Allowing for 30% Extra Load for future additional load.

2.511Kw + 10/100*2.511Kw = 2.762 Kw
Design Load Current =
.
= 14.39 A
The maximum allowed voltage drop is 5% of 240 V0lts = 12V
= volts = Vd = I x ∂ x L Volts
Since the CU’s are approximately 45 m from Maintenance workshop,
Maximum value of ∂ = Vd /( Ib x L) Volts = 12 / (14.39 x 45) = 18.53 Mv/A/m ,thus a
Armorued cable of 4mm2 with a voltage drop of 12 Mv/A/m is chosen. Giving a total
voltage drop of:
Vd = 14.39 x 12 x 45 x 10-3 Volts = 7.77 Volts.
The MCCB chosen is 20 A.
Since ; Ib≤ II ≤ Ic
Where:
conditions
Ib = 14.39 A, II = 20 A Ic = 37 A.
……………………………………………..end……………………………………………

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