Electricity is an essential part of modern life. It arrives at a home from the local utility company by power lines. Most homes have three-wire service with two hot wires and one neutral. The main panel is typically found right next to or beneath a meter. It is considered the central distribution center for all of the electrical circuits throughout a home. A circuit is a journey that begins and ends at the same place. It begins at a power source, powers the devices needing electricity on the circuit and then returns to the power source, a full circle process.
When a repair is done on a home or if a problem arises, the power to the circuit will need to be turned off. This is accomplished by turning off the dedicated circuit breaker in the main panel. Power is very hazardous and oftentimes many people do not take into account how dangerous it can be. However, many safety devices have been installed to protect the home.
It is important to understand all the basics of an electric panel and how it works.
Inside the Electric Panel Door
When the panel door is open, one can access all of the circuit breakers or fuses in the panel. Generally, one of these panels feed the entire house, however some larger homes have multiple panels or situations where a subpanel was installed to serve an addition. Circuit breakers are typically stacked and are controlled with an ON or OFF lever. You will also see a large double pole circuit breaker or the Main, which powers all the circuit breakers below it. The electoral code has required since 1994, that each breaker be specifically identified as to what the breaker serves. Labels must be unique to each breaker. Redundant use of phrases such as “General lighting and outlets” is not allowed. For panels with fuse instead of breakers, there will be many screw in fuses instead of breakers, however the function is the same.
Fuse boxes are still found in older homes. A fuse is responsible for breaking the circuit or connection when there is too much current. This protects the wiring and the appliance itself. The wire in a fuse will melt when there is too much current flowing into it. These fuses screw in and out like light bulbs. If one blows, this means that is metal strip has broken and the window may be discolored. When replacing a fuse, make sure to choose one with the proper amperage. Because of the “one time use” nature of fuses and age factors, fuse panels are rabidly being replaced with newer breaker panels.
Inside the Electric Panel
The interior panel cover or “dead front” usually is held in place with 4 to 6 screws. The screws used are special to electric panels. They are blunt tipped and not threaded at the ends so that they do not cut through insulation. Panel covers should only be removed by experienced personnel, such as, home inspectors, electricians and professional handymen. Inexperienced, untrained persons, such as the average homeowner, should NOT enter and electric panel. It can kill.
Electric Circuit Breakers
Power comes directly from a utility power line through a meter into the service panel. A main breaker controls the primary feed to the electric panel. The main is also can identify the amperage capacity of the panel. Code requires a clear printed number on the double pole main, identifying it’s capacity. The minimum service to a modern home will be 125 Amps, with larger hoe having 150, 200 or even two 200 Amp panels.
Breakers are important as they tolerate a specific amount of amps or current flow before they automatically open or break the circuit. Each separate circuit has its own breaker switch. They should all be labeled accordingly.
There are different types of circuit breakers – single pole breakers proving 110 watts and double pole breakers providing 220 watts. You might also have single or double pole Ground Fault Circuit Interrupter Breakers. GFCIs help to protect an entire circuit from ground faults. They are typically used on circuits where the likelihood of shock is higher such in kitchens, laundry rooms and bathrooms. They can stop current flow in just 25 milliseconds, which protects the home and its occupants greatly. Home built since 2004 may also have Arc Fault Circuit Interrupters on outlet circuits to help prevent fires caused by damaged wires.
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Hot Bus Bars
The two thick wires feeding from the main are known as the hot bus bars. They typically carry 120 volts from the meter and feed it through the two hot bars in the panel. These bars also provide power to circuits. The number of bus bars can vary based on the circuit breaker they are connected to. A single pole circuit breaker provides 120 volts with just one hot bus bar while double pole circuit breakers needs 240 volts or two hot bus bars.
Neutral Bus Bar
Once power leaves the panel through these black wires and does it work, it returns back to the panel through the neutral circuit, which is directly connected to the neutral bar. It is attached to the service panel. Its job is to collect all of the neutral white wires from the different circuits. It also connects the main circuit neutral wire where it will return the current back to the transformer.
A home’s grounding wire connects the neutral bar by grounding the circuits to the earth ground with ground rods or metallic cold water pipe attachments.
A grounding bar can be part of the neutral bar or found separately in modern panels. It collects all of the ground wires from circuits and ties them back into the neutral bar.
Common Electric Panel Issues
- There should be only one wire the wire nut of any breaker. Some breakers have multiple nut positions.
- The wire size (gauge) must be matched to the breaker ampacity. A wire can be smaller than required, but never smaller.
- All of the wires running from the breakers, into the home, must be copper. If your home was built between 1965 and 1975 and has aluminum distribution wires, you will need repairs.
- The wire from the electrical meter, to the main breaker, may be aluminum. If it is, the connection to the main breaker must be coated with a rust inhibitor.
- All wires running from a breaker, into the house, should have black or read insulation. This designates that a wire is “hot”. Double pole (220) circuits where not grounded before 1996. As a result, many 220 circuits have a what neutral designated wire used as a hot. It should be recolored black or red.
- Modern, large double pole devices such as dryers, AC compressors and ovens are more efficient and use less Amps than older equipment. If you install newer equipment, confirm that the breaker size in the panel matches the unit need.
- Installing a “whole house” surge arrestor or power conditioner in your panel in inexpensive and can save you from expensive equipment failure.
- If your electric panel was manufactured by Federal Pacific Electric, it should be evaluated by a professional