Keeping to Code: Considering Power Company Requirements

You'll likely need to jump through some hoops to get power to your home. You must choose the service's location and proper size, and then get all the required permits. Other considerations, such as whether you install overhead or underground service, may be up to you or your power company. The only way to sort out your exact requirements is to make phone calls or personal visits to your power company's building code office and meet with the building inspectors.

Getting permitted

A homeowner can do his own wiring in his own home without hiring a licensed electrical contractor. In most areas, or jurisdictions, the owner must be living in the home or intend to live in the home. If you plan to do extensive electrical work, you're usually required to get a permit. The process usually goes as follows:

1. Find the authority that has jurisdiction, which can be your township, city, county, state, or tribe.

2. You fill out the required form and take it, or mail it, along with the permit fee, to the authority.

3. The authority reviews the form, accepts your money, and issues the permit.

Some jurisdictions have a flat fee for a new construction home-wiring project. You may have to itemize the number of circuits, receptacles, fixtures, and so forth to determine the inspection fee.

4. The electrical inspector visits your project site and checks the work.

If a discrepancy (code violation) is found, you're told how and when to correct the problem.

Installing in light of code requirements

When you install electrical service for a home, whether it's new construction or an upgrade, the electrical code requires that you do a load calculation to determine the correct size for your electrical service. Most jurisdictions don't enforce this requirement, but for safety's sake it's worth doing. The minimum service size allowed to supply a residence is one that carries a total electrical load of 100 amps. With all the circuits needed in a modern home, you should usually install a 200-amp service panel with 40 circuits unless the load calculations require a larger one.

Load is calculated in volt amps (VA), which is the product of volts times amps. For a residence, the load calculation includes a general lighting load of 3 VA per square foot of habitable space, plus any additional loads present. For the service load, the first 3,000 VA are calculated at 100-percent usage and any remaining load is calculated at 35-percent usage. The usage percentages are called demand factors. Demand factors are applied because it's unlikely everything will be on at the same time. If the load calculation is in excess of 120,000 VA, the demand factor is 25 percent for the remainder of the load in excess of 120,000 VA. You must also add in a minimum small-appliance load of 3,000 VA for the kitchen and 1,500 VA for the laundry. The results are added to determine the total calculated load.

Table 1 shows a sample load calculation for a 2,000-square-foot home. As you can see in the table, the total calculated load is 19,125 VA. To determine the minimum amperage you need for your electrical service, divide the calculated VA load by 240, which is typical residential voltage:

19,125 VA Divided by 240 volts = 79.69 amps

Table 1 shows an 8,000-VA load for an electric range and a 5,500-VA load for an electric dryer. Adding these loads brings a total of 19,125 VA. If the range or dryer were gas, you'd eliminate them from the calculation. If your project has any additional loads, such as a furnace or air conditioner, they have to be added to the load calculation. As you can see, the 2,000-square-foot home in Table 1 needs at least 80-amp service. Code requires at least a 100-amp service for residences.

Table 1: Sample Service Load Calculation

For a 2,000-square-foot home, code requires you to have the following:

• Three or four general lighting circuits to supply lights and receptacles

• Two 20 amp circuits to serve the 3,000-VA kitchen receptacles

• One 20 amp circuit to supply the 1,500-VA laundry receptacle(s)

• One 20-amp circuit to supply the bathroom receptacle(s). (This circuit, although required, doesn't have to be included separately in the load calculation.) This circuit can serve one or more receptacles; it can also be used to serve more than one bathroom.