The electrical load calculation for the buildings has to be calculated in two stages. Once at the conceptual or space planning stage, and again at the detailed design stage. These two calculations are generally done with two different metrics.
The lighting load estimation can be carried out on the basis of the
lighting power density tables (Table 7.1 of the ECBC) an excerpt of which is
given below.
Table 7.1 : Interior Lighting Power-
Building Area Method
|
Sl.No
|
Building Area Type
|
LPD (W/m)
|
|
1
|
Automotive Facility
|
9.7
|
|
2
|
Multifamily Residential
|
7.5
|
|
3
|
Convention Center
|
12.9
|
|
4
|
Museum
|
11.8
|
|
5
|
Dining: Bar Lounge/Leisure
|
14
|
|
6
|
Office
|
10.8
|
|
7
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Dining: Cafeteria/Fast Food
|
15.1
|
|
8
|
Parking Garage
|
3.2
|
|
9
|
Dining: Family
|
17.2
|
|
10
|
Performing Arts Theater
|
17.2
|
|
11
|
Dormitory/Hostel
|
10.8
|
|
12
|
Police/Fire Station
|
10.8
|
|
13
|
Gymnasium
|
11.8
|
|
14
|
Post Office/Town Hall
|
11.8
|
|
15
|
Health care-Clinic
|
10.8
|
|
16
|
Religious Building
|
14
|
|
17
|
Hospital/Health Care
|
12.9
|
|
18
|
Retail/Mall
|
16.1
|
|
19
|
Hotel
|
10.8
|
|
20
|
School/University
|
12.9
|
|
21
|
Library
|
14
|
|
22
|
Sports Arena
|
11.8
|
|
23
|
Manufacturing Facility
|
14
|
|
24
|
Transportation
|
10.8
|
|
25
|
Motel
|
10.8
|
|
26
|
Warehouse
|
8.6
|
|
27
|
Motion Picture Theater
|
12.9
|
|
28
|
Workshop
|
15.1
|
As far I know (Readers,
please correct me in this) there is no standard for calculating the power
allocation for socket outlets in India. The BS standard of 30w/sqm may seem to
be a little on the high side for an Indian situation. A more conservative
number would be 20W/sqm. The same can be considered in offices. However the HVAC
load has to be added in the case of offices.
The calculation at the two stages follows the general sequence
given below.
a) Estimation of load at the concept design stage.
1)
Data required
Area of the
building
The total carpet
area of the building with the split up for the various area
Loads of the
various other equipments.
2)
Calculation
Multiply each of
the areas by the appropriate power density as per the tables above.
Add the load of
the common areas and other equipment.
The total will give the estimated total
power requirement for the building. This forms the basis for the space planning
for the substations, panel rooms and riser sizing.
b) Load calculation at the detail design stage
The load calculation at this stage requires
a more thorough approach. However since much more data is available at this
stage it becomes more of a task of collating all the available data, interpreting
and using the data properly.
1)
Data collection
·
Number of lighting points
·
Number of power points
·
Common area loads
·
List of equipments and their loads
·
Operating times/frequencies for these loads.
2)
Making a load list with the available data and
calculation.
·
The load list should contain as much detail as
possible regarding the loads.
·
Calculate the operating, maximum loads.
·
Size the cables, panels and transformer
accordingly.
A sample format as shown below can be used for the
calculation. The application of the diversity factor in calculating the total
load is another matter which I will cover in another article.
Format for load list
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Sl.No
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Description
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Rated
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Emergency
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Life
Safety
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kW
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kVA
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kW
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kVA
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kW
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kVA
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Sum
Total
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The load list above can be used for the calculation of the
loads in the various conditions. One important point to be noted is that the
diversity factor will have to apllied for the loads to arrive at the final
sizing of the equipments.
Ref:
1)
National Building code
2)
ECBC User guide
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