1. EE4503 Electrical Systems Design
Load Calculation

2. Topics Load Calculation (E.I.T.)
Load Calculation by Adding Branch Circuit
Load Calculation for condominium
Load Estimation

3. Load Calculation (E.I.T.) lighting
Building
Lighting (VA)
Demand Factor (%)
Residential Area
 2,000
> 2,000
100 35
Hospital
 50,000
> 50,000 40 20
Hotel, Condominium
 20,000
20,001 – 100,000
> 100,000 50 30
Warehouse
 12,500
> 12,500
Other

4. Load Calculation (E.I.T.) receptacles
Total Load from Receptacle
Demand Factor (%)
Non residential area
 10kVA
100
> 10kVA 50
Residential area
𝐿 𝑚𝑎𝑥 +0.4 𝐿 𝑟

5. Load Calculation (E.I.T.) Demand Factor of Appliances
Building
Lighting (VA)
Demand Factor (%)
Residential Area
Kitchen
Hot Water
Air Condition
10A+30% of extra
first two + 25% of other
100
Office, Store
First maximum device + 80% of the second max. + 60% of the rest
100% of the largest + 25% of the rest
Hotel, Other
Same as Office 75

6. Load Calculation by Adding Branch Circuit
Add of all branch circuit
Then multiply by the demand factor
Number of Panels
Demand Factor (%) 1
2-3
4-6
7-10
> 10
100 90 80 70 60

7. Load Calculation for Condominium
Load: common area + individual room
Type
Number of Rooms
Coincident Factor (%)
Residential
1-10
11-20
21-30
31-40
> 41 90 80 70 60 50
Non residential
> 11
100 85

8. Load Estimation Quick estimate of the load
Many common tables, just refer to one

9. Load Estimation

10. Load Estimation

11. Load Estimation (E.I.T.) lighting
Type
VA/m2
School 25
Computer Center, Meeting Room, Kitchen 20
Walk way, Balcony 8
Cafeteria 18
Hospital – Operation Room
100
Hospital – Patient Room 14
Office, Shopping Store 30
Drawing Room 60
Laboratory 50

12. Load Estimation (E.I.T.) receptacles
Type
VA/m2
Auditorium, Cafeteria, Church, Sport Complex 2
Drawing Room 7
Hospital 10
Machine Room 15
Office
School

13. Load Estimation (E.I.T.) air condition
Type
VA/m2
Bank 80
Department Store 50
Hospital 70
Office
Grocery Store 90
Cafeteria

14. Reference Electrical Systems Design: ประสิทธิ์ พิทยพัฒน์
Depend on the area, end-user can connect to the “meter” of the authority in three ways.