EE 513 Electrical System Design
Objectives:
Describe demand factor in different electrical loads
2. Choose the appropriate demand for cooking
equipment in dwelling units and commercial
occupancies using tables.
3. Compute for demand of several cooking equipment
of different sizes.
1.
Demand Factor
 The ratio of the maximum demand of a system, or part
of a system, to the total connected load of a system or
the part of the system under consideration
 Applied when asked for the minimum size conductor
or service size
 Results to a reduction in conductor size
 Results to reduction in cost
Permitted Demand Factor
1.
2.
3.
4.
5.
Lighting
Receptacles
Cooking equipment
Clothes dryers
Fastened in place appliances
Reason
 How many lights do you turn on at night?
 Do you use all the receptacles at home?
 All the lights are not on at the same time, nor will all
the receptacles be fully loaded at the same time
Demand for Household electric
ranges and etc.
Demand for Household electric
ranges and etc.
Examples:
1.
What is the demand for a 12kW appliance?
 8 kW
2. What is the demand load for two 12kW ranges?
 11 kW
3. What is the demand load for 4 – 3kW counter
mounted cooktops?
 7.92 kW
4. What is the demand load on the service for six 5 kW
wall-mounted ovens?
 12.9 kW
Examples:
5. What is the demand load on the service for two 3
kW cooktops and two 5 kW ovens?
 11 kW
6. What is the feeder demand for a 12 kW range and a 4
kW cooktop?
 11.2 kW
Note 1: Equal sizes over 12 kW
through 27 kW
 For ranges individually rated more than 12 kW but not
more than 27 kW, the maximum demand in Column C
shall be increased 5% for each additional kW of
rating or major fraction thereof by which the
individual ranges exceeds 12 kW
Examples:
What is the demand for a 14 kW range?
1.



14 kW – 12 kW = 2 kW, 2kW x 5% = 10%
Demand for 12 kW is 8 kW
8 kW x 1.10 = 8.8 kW
What is the demand for two 14 kW ranges?
2.

12.1 kW
What is the demand for 4 – 15 kW ranges?
3.

19.55 kW
4. What is the demand for 20 – 16 kW ranges?
5. What is the demand for 30 – 17 kW ranges?

56.25 kW
3
Note 2 Unequal sizes over 8
4kW
 Over 83 4kW through 27 kW ranges of unequal ratings
 For ranges individually rated more than 12 kW and of
different ratings but none exceeding 27 kW, an AVERAGE
VALUE of rating shall be computed by adding the ratings
of all the ranges to obtain the total connected load (USING
12kW for any range rated less than 12 kW) and dividing
by the total number of ranges;
 the maximum demand in Column C shall be increased by
5% for each kw or MAJOR FRACTION THEREOF by
which the AVERAGE VALUE exceeds 12 kW.
Note 2 Sample Calculation
1.
What is the demand load for three 9 kW ranges,
four 14 kW ranges, and five 15 kW ranges?
3 − 12 𝑘𝑊 = 36 𝑘𝑊
4 − 14 𝑘𝑊 = 56 𝑘𝑊
5 − 15 𝑘𝑊 = 75 𝑘𝑊
12
167 𝑘𝑊
167 𝑘𝑊
= 13.9 𝑜𝑟 𝟏𝟒 𝒌𝑾
12
Note 2
 As in note 1
14 𝑘𝑊 − 12 𝑘𝑊 = 2𝑘𝑊
2 𝑘𝑊 𝑥 5% = 10%
From Column C
maximum demand for 12 ranges is 27 kW
27 𝑘𝑊 𝑥 1.10 = 𝟐𝟗. 𝟕 𝒌𝑾
Note 2 Sample Calculation
1.
What is the demand load for two 10 kW ranges, six
15 kW ranges, and seven 16 kW ranges?
2 − 12 𝑘𝑊 = 24 𝑘𝑊
6 − 15 𝑘𝑊 = 90 𝑘𝑊
7 − 16 𝑘𝑊 = 112 𝑘𝑊
15
226 𝑘𝑊
226 𝑘𝑊
= 15.06 𝑜𝑟 𝟏𝟓 𝒌𝑾
15
Note 2
 As in note 1
15 𝑘𝑊 − 12 𝑘𝑊 = 3 𝑘𝑊
3 𝑘𝑊 𝑥 5% = 15%
From Column C
maximum demand for 12 ranges is 30 kW
30 𝑘𝑊 𝑥 1.15 = 𝟑𝟒. 𝟓 𝒌𝑾
Note 3
 All note 3 does is grant you permission to use Columns
A and B instead of Column C
Note 4 Branch Circuit
 It shall be permissible to compute the branch circuit load
for one range in accordance with the table.
 The branch circuit load for ONE wall-mounted oven or
ONE counter-mounted cooking unit shall be the
NAMEPLATE RATING of the appliance.
 The branch circuit load for a counter-mounted cooking
unit and not more than two wall-mounted ovens, all
supplied from single branch circuit and located in the same
room, shall be computed by adding the nameplate rating of
the individual appliances and treating TOTAL as
equivalent to one range.
Note 4 Sample Calculations
What is the demand for one 4 kW cooktop and two
4 kW ovens
4 𝑘𝑊 + 4 𝑘𝑊 + 4 𝑘𝑊 = 12 𝑘𝑊
treat as one 12 kW range
Column C = 8 kW demand
2. What is the demand for the service for one 4 kW
oven and two 5 kW ovens?
4 𝑘𝑊 + 5 𝑘𝑊 + 5 𝑘𝑊 = 14 𝑘𝑊
Column B = 55% demand
14 𝑘𝑊 𝑥 55% = 𝟕. 𝟕 𝒌𝑾
1.
3. What is the demand for the branch circuit for one 4
kW oven and two 5 kW ovens?
4 𝑘𝑊 + 5 𝑘𝑊 + 5 𝑘𝑊 = 14 𝑘𝑊
Apply note 1
14 𝑘𝑊 − 12 𝑘𝑊 = 𝟐 𝒌𝑾
2 𝑘𝑊𝑥 5% = 10%
Column C for ONE range is 8 kW
8 𝑘𝑊 𝑥 1.10 = 𝟖. 𝟖 𝒌𝑾