Example No. D1(b) One-Family Dwelling
Assume same conditions as Example No. D1(a), plus addition of one 6-ampere, 230-volt room air-conditioning unit and one 12-ampere, 115-volt room air-conditioning unit,* one 8-ampere, 115-volt rated waste disposer, and one 10-ampere, 120-volt rated dishwasher. See Article 430 for general motors and Article 440, Part VII, for air-conditioning equipment. Motors have nameplate ratings of 115 V and 230 V for use on 120-V and 240-V nominal voltage systems.
From Example No. D1(a), feeder current is 78 amperes (3-wire 240 volts).
|
Line A |
Neutral |
Line B |
|
|
Amperes from Example No. D1(a) |
78 |
61 |
78 |
|
One 230-V air conditioner |
6 |
6 |
|
|
One 115-V air conditioner and 120-V dishwasher |
12 |
12 |
10 |
|
One 115-V disposal |
8 |
8 |
|
|
25% of largest motor (see 430.24) |
3 |
2 |
2 |
|
Total amperes per line |
99 |
83 |
104 |
|
Therefore, the service would be rated 110 A. |
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*(For feeder neutral, use largest of the two appliances for unbalance.) |
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