Breaker, Breaker

Circuit breakers, along with fuses, are known as overcurrent protective devices. They protect you, your electrical equipment, and your wiring. They are matched to the ampacity of a circuit’s conductors, and they shut the current down if there’s an overload or a short-circuit. Breakers are clearly marked (15, 20, 30 amp, and so on) and must be used accordingly. You can’t stuff a 20-amp breaker into your panel box and use it on a 15-amp circuit, especially if the circuit only has 14-gauge wire. This is a recipe for fire because you’ll be allowing the wire to carry more current than it’s designed to carry, and the breaker won’t sense the problem and thus won’t trip.
Breakers are either single pole or double pole (sometimes referred to as a two-pole breaker). Double-pole breakers are used for 240-volt circuits and draw power from each of the 120-volt hot wires entering the panel. A double-pole breaker can be either a single device or two single-pole breakers tied together so they’ll both shut off at the same time.

Grounding Your Panel

A big safety advantage in newer service panels over old fuse systems is the fact that they’re grounded. The code is very specific about grounding procedures including
…
➤ The size of the grounding conductor.
➤ What is and is not an acceptable grounding electrode.
➤ Bonding requirements and the use of clamps and bonding bushings.

A service panel is grounded twice when possible: once to your water pipes (assuming they’re metal and not plastic) and once to a grounding rod buried in the ground. When a grounding rod cannot be used due to soil conditions, a length of copper wire can be buried directly in the earth (a minimum of 21/2 feet deep) or encased in concrete at least two inches thick that has direct contact with the ground (usually a foundation).
There also are other means of grounding the system (depending on your soil and house construction). The materials allowed, their installation, and their dimensions are all spelled out extensively in Article 250 of the code. Electricians know this stuff by heart because they use it every day. You, on the other hand, will never use it again, so consider calling an electrician for your panel installation.

Location Is Everything

The code is a little particular about where you can situate a service panel. In addition to being as close as possible to the service conductors’ entry point, a service panel …

➤ Must have clear access to it (a minimum of a 30-inch wide by 36-inch deep uncluttered space).
➤ Cannot be installed inside cabinets or above shelving or any other encumbrance. It also cannot be installed in a bathroom.
➤ Must have a working space with 61/2 feet of headroom around it.

In other words, the panel has to be in a clear and accessible area, and it must be readily visible to anyone looking for it. You can’t store your skis or bikes in front of it, and you must be able to open the panel door a full 90 degrees until it’s flat against the wall. Section 110-26(d) of the NEC calls for some illumination to be provided around the panel so that you or an electrician can see what you’re doing if you have to access the panel. Although the code doesn’t detail how much lighting you need to supply, you want to be able to comfortably read the panelboard (the breakers) and the panelboard directory inside the door.

Anatomy of an Electrical Service Panel

A service panel must conduct electricity to individual breakers, must receive and
route the current being returned through the neutral conductor, and must provide a
grounding medium for the system. In a sense, it’s the most powerful electrical device
in your system. Remember, the conductors and cable that come into and leave your
service panel include …

➤ Two hot conductors.
➤ One neutral conductor.
➤ One grounding conductor that

originates in the panel. The two hot conductors energize the panel—and thus the breakers—via two hot bus bars, which are located in the center of the panel. The black or red outbound wires are connected to the circuit breakers that clip or slide into the hot bus bars. These wires supply the current to electrical loads throughout your house. The neutral wires are connected to the neutral bus with setscrew terminals. A grounding bus bar connects the various grounding conductors from the circuits to the panel’s main grounding conductor. The grounding bus bar is bonded to the neutral bus bar. This is the only place the neutral and grounding conductors are tied together. In addition to individual breakers, most service panels have a single main service disconnect in the form of an individual breaker or a series of high-amperage breakers connected together. The code requires that you be able to shut the entire panel down with a maximum of six hand movements. (That is, the panel can’t need more than six switches or breakers to disconnect all of your home’s electrical equipment.) An old panel might require up to six moves to shut everything down, but new service panels all have a single main shutoff, as previously described. The code requires that this main disconnect be as close as possible to the service conductors’ point of entry into the building. In other words, you can’t bring the service conductors into one corner of your basement and then install the service panel 15 feet away while exposing the conductors. (Certain exceptions do apply.)

New Service/Old Service Electrical Service

Unless you’re rewiring your entire house (which isn’t likely unless you’re doing a major remodel), you’ll need to connect your new service panel with at least some of the existing circuits. This usually is not included in the cost of the service change. It really depends on the purpose of the upgrade. In addition, if you have an old fuse system, you will most likely replace the following (again, at an extra cost):

➤ The major appliance circuits
➤ The kitchen and bathroom circuits
➤ The water heater and possibly the furnace circuits

Existing branch circuits for lighting often can be left alone and simply tied into your new panel. (Each will have to be checked, of course.) If you are replacing an existing service panel on a three-wire grounded system with a higher-amp panel, you also will need to connect to the existing service. Only when you’re completely rewiring your home can you ignore the existing service and its location.

Going Underground

I’m a big fan of underground service conductors. New developments almost always have them, but a new house in an established neighborhood might not, depending on which side of the street it’s located. If you’re on the same side as the utility poles, consider burying your line. It will involve digging a trench at least 18 inches deep (check local requirements) and possibly doing so across a neighbor’s property. A buried cable results in a much cleaner appearance, and there’s no chance of it being damaged during severe weather, massive flooding notwithstanding. (The utility’s power lines can still go down, however.) It’s also out of the way when you have to set up ladders to paint or to work on your roof.
With an underground service, your utility company installs service lateral conductors (which may or may not have to be contained in conduit, depending on your local code). The conductors then enter the meter, via at least a short section of conduit, from underneath the ground. As with any outdoor wiring done by an electrician, you can save yourself some money by doing the digging and trenching yourself or by hiring it out to a less-expensive laborer than an electrician.

Overhead and Exposed

It’s a lot simpler to install an overhead service in an established neighborhood than it is to start tunneling under streets and sidewalks to run conductors underground. Overhead wires are exposed to the weather, however, and this means your service can be disrupted if a tree branch falls on it during a high wind. Modern electrical service consists of two hot conductors and one neutral conductor coming into your home. They come out of a transformer, which steps down the voltage, and must clear roofs, fences, and outside structures as they connect to your service head on top of your service mast. The conductors form a drip loop as they enter the service head so that any rain landing on them will not run down the mast.
The service conductors are pulled through the mast and then pass through the meter (which records your electricity usage). Your utility connects the wires coming out of the weather head to the conductors (service lateral conductors or overhead wires) coming from the pole and the conductors to the meter, which the company usually supplies. Rules for installing an overhead service govern …

➤ The location of the meter.
➤ Clearance requirements for the conductors.
➤ Securing and supporting the service mast and raceway to your house.

Your utility company determines where the meter will be located. The company’s main concern is that the overhead conductors will be in a safe, unencumbered location. The clearance requirements for the conductors and the length of your service raceway (the mast and head) must take the following factors into account:

➤ The distance from the service mast to the utility pole
➤ The pitch of your roof
➤ Whether you’re using an IMC, PVC, or steel raceway (conduit)
➤ The proximity of windows to the proposed location

Finally, the conduit or raceway must be secured properly so it doesn’t loosen or bend. Any hole you drill for the raceway or its supports must be sealed so you don’t get water leaks. Your local electrical inspector can give you more information about clearance requirements and securing your service mast.
As you can see, this is a complicated process—and we haven’t even gotten to the service panel yet! In case you were wondering, you can’t attach any other cables (phone or TV, for example) to your service mast.