# Example No. D2(b) Optional Calculation for One-Family Dwelling, Air Conditioning Larger than Heating [See 220.82(A) and 220.82(C)]

The dwelling has a floor area of 1500 square feet exclusive of an unfinished cellar not adaptable for future use, unfinished attic, and open porches. It has two 20-ampere small appliance circuits, one 20-ampere laundry circuit, two 4-kW wall-mounted ovens, one 5.1-kW counter-mounted cooking unit, a 4.5-kW water heater, a 1.2-kW dishwasher, a 5-kW combination clothes washer and dryer, six 7-ampere, 230-volt room air-conditioning units, and a 1.5-kW permanently installed bathroom space heater. Assume wall-mounted ovens, counter-mounted cooking unit, water heater, dishwasher, and combination clothes washer and dryer kW ratings equivalent to kVA.

Air Conditioning kVA Calculation

Load Included at 100%

Air conditioning: Included below [See Item 1 in 220.82(C)]

Space heater: Omit [See Item 5 in 220.82(C)]

1500 sq. ft. at 3 volt-amperes

4500 VA

Two 20-amp. small appliance circuits at 1500 volt-amperes each

3000 VA

Laundry circuit

1500 VA

2 ovens

8000 VA

1 cooking unit

5100 VA

Water heater

4500 VA

Dishwasher

1200 VA

Washer/dryer

5000 VA

32,800 VA

1st 10 kVA at 100%

10,000 VA

Remainder at 40% (22.8 kVA x .4 x 1000)

9,120 VA

19,120 VA

Air conditioning

10,080 VA

Total

29,200 VA

Calculated Load for Service

Feeder Neutral Load (per 220.61)

Assume that the two 4-kVA wall-mounted ovens are supplied by one branch circuit, the 5.1-kVA counter-mounted cooking unit by a separate circuit.

 1500 sq. ft. at 3 volt-amperes 4500 VA Three 20-amp circuits at 1500 volt-amperes 4500 VA Subtotal 9000 VA 3000 volt-amperes at 100% 3000 VA 9000 VA - 3000 VA = 6000 volt-amperes at 35% 2100 VA Subtotal 5100 VA

Two 4-kVA ovens plus one 5.1-kVA cooking unit = 13.1 kVA.

Table 220.55 permits 55% demand factor or

 Subtotal from above 5100 VA Ovens and cooking unit: 7200 VA x 70% for neutral load 5040 VA Clothes washer/dryer - 5 kVA x 70% for neutral load 3500 VA Dishwasher 1200 VA Total 14,840 VA

Calculated Load for Neutral

Pocket Guide to the National Electrical Code(R), 2005 Edition (8th Edition)
ISBN: 0131480014
EAN: 2147483647
Year: 2004
Pages: 120