Installing an Electrical Service
Once you know the steps, mounting and wiring a meter base and breaker panel are easier than you might think.
Synopsis: A step-by-step guide to selecting, sizing, locating, and installing the main components—the meter base, main breaker, and breaker panel—of a new residential electrical system, including a discussion of how to size and install the various types of cable used in the system.
Most people have only a vague sense of how a house’s main electrical panel works, so they wisely keep their hands out of it. But before power is hooked up to a new home, the installation of the meter base and breaker panel is a series of straightforward tasks. Only a few specialized tools are needed, and many of the techniques are the same as those used in branch circuit wiring (See “Rough Electrical Wiring“).
Of course, the trick lies in understanding the National Electrical Code (NEC), knowledge that an electrician gathers over years of apprenticeship and practice. I can’t write an article to replace an electrician’s years of experience, but I can review the essential stages of the process along with the essential aspects of the code. In most jurisdictions, homeowners can install their own electrical service as long as they do the homework, pull the permit, and collaborate with the inspector and the utility company. Changing out an energized, existing service, however, is altogether different and is best left to a qualified, licensed electrician.
The main parts and pieces
The meter base is where the utility mounts its meter, and the breaker panel is where circuit breakers tie into their individual circuits. The utility has specifications for acceptable meter bases. They can be configured several ways, as shown in the drawings below. Also key is the main breaker, which is integral to either the meter base or the breaker panel. I prefer the main breaker to be in the meter base. Local code frequently requires this location anyway because in the case of a house fire, rescue workers can easily shut down the power. In the project shown here, the meter base and the main breaker are outside, and the breaker panel is in the basement.
The utility and the building department specify the meter base’s location on the house. My local utility wants it within 36 in. of the corner of the house nearest the transformer, with the center of the meter 60 in. above finished grade. The NEC requires clear workspace 30 in. wide, 36 in. deep, and at least 80 in. high in front of any meter or breaker panel, inside or out. The NEC also specifies clearances from the ground, roof, and windows to the weather head (the top of the mast where an overhead utility cable reaches the house) and the utility cables. Meter bases must be mounted securely, so I lag-screw them to the framing.
Ideally, the breaker panel mounts back to back with the meter base, connected by a short length of metal conduit or a fitting called a chase nipple through which feeder cables will run. This configuration isn’t possible, however, when the breaker panel is in the basement as shown here. In this situation, you have to run a heavy-gauge feeder cable from the meter base to the breaker panel.
For more photos, drawings, and details, click the View PDF button below.
From Fine Homebuilding #150
