• Example :
G+7 floor : Residential+ commercial complex
( Commercial for super market)
-Under ground parking
-Ground floor→super market→1500 sqft
-1 to 7 floor→Resident→1500 sqft
1 sqft for commercial 3.5 watt only lighting and In gulf, 4.5 watt only lighting.
For commercial,
10000 sqft × 3.5
= 35000 w
= 35 kw
• HAVC → 120 sqft - 1 ton (1 ton- 1400w)
10000 - ?
= 10000 × 1400/120
= 14000000/120
= 116666.6 w
= 116666.6/1000 = 116.66 KW
Therefore, take 120 kw for AC load.
Total connected load for commercial -
35+ 120 = 155 kw
Extra 25% = 155 × 1.25 = 193.75
Therefore, take 195 kw
Maximum demand = 0.8
Peak demand = max. demand× T.C.l
= 0.8 × 195
= 156 kw
Therefore, transformer selection for commercial
= KVA →kw÷P.F
156÷ 0.8 = 195kw
Loading factor = 195/0.7 = 278.75 KVA
Therefore, 315 transformer is recommended for commercial
Main circuit breaker for L.T panel for super market
A = KVA × 1.4
= 315 × 1.4
= 441 A
# 630 A MCCB is recommended
Electrical load calculation for residential complex.
Common load :
Left = 7.5 HP × 2 = 11.19 kw
Borewell →5HP = 3.73 kw
Pump → 5HP = 3.73 kw
Parking = 5kw
Loby = 5kw
Flat :
3BHK - 7.5kw
4BHK - 10 kw
Total flat in each floor - 6
6(flat) × 7 (floor) = 42 flats
= 42 × 7.5 = 315 kw
T.C.L = 315 + 11.19 + 3.73 + 3.73 + 5 + 5
= 343.65 kw
Demand factor = 0.6
Peak demand = T.C.L × 0.6(D.F)
= 345 × 0.6
= 207 kw
KVA = KW ÷ P.F = 207 ÷ 0.8 = 258.75
Loading factor = 258.75/0.7 = 369.6
Therefore, 400 KVA transformer is recommended for Residential complex.
Circuit Breaker for Residential for L.T panel
A = KVA × 1.4
= 400 × 1.4 = 560 A
Therefore, 630 A MCCB is recommend.
When load is connected in three-phase and distribution in 3 different phases. Then, we have to take C.B double the Amper.
Each flat per kw - 7.5 kw
7.5 × 2 = 15A
15 × 2 = 30 A
P.F = 0.8 @ 6A
P.F = 0.6 @ 8A
• Example :
A - block
B - block
C - block
Light - 60 W
Fan - 100 W
AC - 1400 W
5A - 200 W
15A - 1000 W
A- block = 30 class room
Each class room load :
4 - light, 4 - fan, 1 - AC, 5A - 4 socket
, 15A - 1 socket.
B- block = 25 class room
Each class room load same as A-block
Office : 20- light, 10- fan, 5A - 16, 15A - 6.
C- block = over all canteen -20kw
Conference hall : 40 - light, 20- fan, 5A - 10, 15A - 6.
Common load : washroom, outdoor lighting, water pump etc - 15kw
Calculate :
A- block
B- block
C- block
T.C.L = 20+ 12.4
= 32.4 kw
= 32.4× 1.9 = 61.58
= 61.58× 1.25 = 76.95
Common load : 15 kw
15 kw × 1.9 = 28.5
28.5 × 1.25 = 35.6
T.C.L = A- block+ B - block+ C - block+ common load
= 115.2 + 114.4 + 32.4+ 15
= 277 kw
Demand factor = 0.6
Peak demand = 277 × 0.6 = 166.2 kw
KVA = KW/ P.F = 166.2/0.8 = 207.75
Loading factor = 207.75/0.7 = 296.78KVA
315 transformer is recommended.
Figure : SLD
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