Inlet service panel box

Some panel-box covers have a door. If there is a door on the panel box, lift or swing it open. WARNING: Do not remove the panel cover. The cover should be removed only by a professional inspector or electrician because of the danger involved with exposed electrically hot wires. Some homeowners remove the panel cover when doing home wiring and then forget to replace it. Others remove the cover and then cover the panel box with a picture. They think this provides easy access. It does-for children too-and is very dangerous. Panel-box covers should be mounted and securely in place at all times.

When looking at the panel-box cover, note whether any knockout plates or fuses are missing. They represent a potential hazard; it is possible for a child to stick his or her finger in these openings and be electrocuted. If there are openings, they must be permanently blocked off. Check the size and number of the fuses or circuit breakers. There should be at least two 20-amp appliance circuits and one 15-amp lighting circuit for each 500 square feet of floor area. Anything less than this is not considered adequate. Also, if the branch circuits are protected by fuses, note if there are many blown fuses in the area indicating that one or more of the circuits might often be overloaded, a condition that might require installing additional branch circuits.

Panel-box interior

Because of the hazards involved, certain items should not be checked by the home buyer-owner, specifically those items found inside the main panel box. A professional home inspector or licensed electrical contractor checking the interior of the panel box can tell you whether the fuses or circuit breakers are properly sized for their respective branch circuits. Improperly protected branch circuits are found fairly often.

Once the panel cover has been removed, the actual inlet service capacity can be determined. It depends on the size of the inlet service wire only, not on the rated capacity of the panel box or the size of the fuse or circuit breaker used for the master disconnect, if there is one. Figure 12-4 shows a circuit-breaker panel box with a 200-amp master disconnect. A home buyer seeing this would normally believe that the house is supplied with 200-amp electrical service, and rightly so. In this case, however, the inlet service wire is too small to supply 200 amps. When the cover was removed, it was determined that the inlet service was 100 amps and that the master disconnect circuit breaker did not provide the overload protection.

Aluminum wiring

Inspecting the interior of the panel box also reveals whether aluminum wiring was used for the branch circuits rather than copper wiring. Aluminum wiring is considered a potential fire hazard. Between 1965 and 1973, about 1.5 million homes were wired with aluminum, which at the time was approved by the National Electrical Code. It was later found that dangerous overheating occurred at some of the connections in the 15- and 20-amp branch circuits, which resulted in fires.

If aluminum wiring was used, the electrical connections to the receptacles, switches, and light fixtures throughout the structure should be checked by a competent electrical contractor to determine if they have been properly made or show evidence of problems. If the house does have aluminum branch circuits, you should be aware of the following trouble signs:

  • unusually warm cover plates on switches and outlet receptacles
  • a distinctive or strange odor in the vicinity of a receptacle or switch
  • sparks or arcing at switches and outlets
  • periodic flickering of lights (sometimes traceable to faulty appliances or fixtures)

Correcting the problem does not require rewiring the house. Switches and outlet receptacles that are unmarked or marked AL/CU should be replaced with devices that are marked CO/ALR. Or existing switches and outlets can be used, provided short copper pigtails are attached to the ends of the aluminum wires and the devices. It’s also necessary to connect light fixtures with copper pigtails. The home buyer-owner should not attempt to correct this condition.

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Alice's Avatar
Alice replied the topic: #11267
I only hire a licensed electrician to do any electrical work in my condo. Electricity is too dangerous and can cause fires or electrocute someone. I never use a handyman, only a licensed electrician.