Electrical Testing
Tip of the Week: Additional Items of Value in NEC Annex D

Tip of the Week: Additional Items of Value in NEC Annex D

Examples D1(a) and D1(b) help you calculate loads and feeder sizes for a one-family dwelling.

What can you learn from the NEC’s Annex D, Examples D1(a) and D1(b)? Both are for one-family dwellings, but the first one is much longer than the second one. So the first step in making use of these is to figure out why there's such a big difference in length.

The answer: Although they assume the same conditions and are the same problem, the second one adds several more loads to the mix.

So what is the basic problem and why should you care? The problem consists of calculating the loads, and from the results, determining the minimum feeder size and service size for this one-family dwelling.

This example takes you through each step, in the proper order, and provides NEC references at key points. By first providing a basic problem and then a more complicated one, the D1 Examples help you understand the work flow involved (doing the steps in the right sequence).

They also help you understand which loads to account for, given the conditions stated in the problem. For instance, in Example D1(a) you will see that to arrive at the Net Calculated Load, you must account for general lighting, small appliance circuits, laundry, range, and dryer.


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