The way to Determine the Size of Your Main Electrical Service

The way to Determine the Size of Your Main Electrical Service

The way to Determine the Size of Your Main Electrical Service


The main electrical service delivered to the house of yours from the electrical utility company has a total accessible capacity, measured in amps, or perhaps amperes. Most homes have an electric service of between hundred to 200 amps. Amperage is actually a measurement of the volume of electrical energy flowing through wires, and this measurement is able to vary between thirty amps in very old homes that haven’t been updated, to almost as 400 amps in an extremely large home with electrical devices and extensive electrical heating systems.


 Understanding the size of a house’s electrical service is able to help you know if an update is actually needed, or even if the service is actually big enough to deal with an update, like a remodeled kitchen or perhaps room addition.


 How Electrical Current Reaches The Home of yours

Electrical service reaches the home of yours from the power utility through 2 120 volt service wires that provide a combined 240 volts of power (voltage is actually a measurement of electricity’s rate or perhaps pressure of flow). The primary service wires reach the home of yours also through overhead service wires that enter a service mast and pass down through an electric meter into your house, or perhaps through underground wires that also pass through an electrical meter. The very first stop for the electrical service once it enters your house is actually the main service panel.


What the Main Service Panel Does The main service panel is actually the distribution center that splits the main electrical service into individual branch circuits that run through your house to power the lights, outlets, and individual appliances. The primary service panel is generally a gray metal box located somewhere along the inside surface area of an exterior wall. It’s frequently found in a utility area, like a garage, basement, or perhaps furnace room. When it’s placed in a finished living space, it’s often contained inside a finished cabinet mounted on the wall.


 The primary service panel includes 2 hot bus bars that run side-by-side down the panel, and one hot 120 volt service wire is actually attached to each of these bus bars. A home circuit connected to just one bus bar is going to deliver 120 volts of power, while a circuit connected to both bus bars will deliver 240 volts of energy.


 Fuse Box vs. Circuit Breaker Panel

In most homes, the main service panel uses circuit breakers that control and protect the individual circuits. Circuit breakers are specially designed safety switches that prevent individual branch circuits from drawing much more power than the circuit wires can easily handle. Virtually all homes built since the early 1960s use circuit breakers as the power distribution method. Older homes also have circuit breaker panels if their electric service was updated after 1960.


 Where an electric service was installed before the early 1960s and hasn’t been updated, it could use a completely different style of power distribution – a fuse panel which protects individual circuits with screw in or perhaps cartridge fuses.


 The use of fuse panels and circuit breaker panels for residential wiring follows a historical pattern:


 30-amp fuse panel: Installed before 1950, these service panels provide only 120 volt current. Such a service provides insufficient power for modern usage and generally has to be updated.

60 amp fuse panel: Installed from 1950 to aproximatelly 1965, 60-amp fuse panels provide 240 volts of power, but are currently insufficient for most homes. An update is generally needed.

Circuit breaker panel: Since the early 1960s, homes have usually been wired with circuit breaker panels which provide 240 volt current. Early services may provide 60 amps of power, while large houses built today may have 200 amps or perhaps more of energy. Homes with 100-amp or 60-amp service often require an electrical service update during major remodeling or perhaps expansion projects.

Tools and Supplies You’ll Need

Flashlight (if needed)


Inspect the Electrical Meter In many instances, you are able to figure out the dimensions of the home’s electrical service by simply looking at the electrical meter outside the house. Search for the point at which the primary service wires from the utility company enter the house. If electrical service is actually delivered by overhead wires, they are going to enter a metal service pipe that runs down an exterior wall of your house to the meter. When the meter is actually a glass dome mounted on a square metal base, the home most likely has hundred amps of power, while a newer 150 amp or perhaps larger service will have a rectangular base that stretches below the glass dome.


If you notice a glass dome mounted on a round base which is actually the same dimension as the dome, or perhaps a meter located behind a flat glass window which is actually flush with the front of an enclosed metal box, it is likely you have sixty amps of electric service.


Find the Main Service Panel Now, locate the main service panel – a circuit breaker box or perhaps fuse box – inside the home of yours. This panel will often be on the opposite side of the wall where the exterior electrical meter is actually located. In most homes, it will be a vertical gray metal (or sometimes black) box mounted on a wall in a utility area. If the main service panel is actually in a finished living space, it can be enclosed in a finished cabinet of some kind.


Locate and Read the Main Circuit Breaker or perhaps Fuse Block Make sure the floor around the key service panel is actually dry, then open the metal door on the service panel. Inside the panel, you are going to see 2 rows of individual circuit breakers with small toggle levers. These individual circuit breakers are actually numbered, and they control individual branch circuits running through the house of yours. The amperage of these individual breakers will be between fifteen and fifty amps, usually.


At the top end of the 2 rows of branch circuit breakers, there’ll be a main circuit breaker that controls the power to the whole panel. This’s the main circuit breaker, and its amperage rating will something like sixty, hundred, 150, or perhaps 200 amps. In instances that are rare, the main circuit breaker may be mounted with the bottom of the service panel. The main circuit breaker may be bolted in place, or perhaps it could be a snap in breaker similar to those serving branch circuits.


This main circuit breaker dictates how much power can be obtained to the whole house of yours. It’s a double pole breaker, connected to both 120 volt service wires to power both hot bus bars running down through the panel. Turning this main breaker to the OFF position shuts off power to the whole house and most of the branch circuits. The amp rating on this main circuit breaker identifies your electrical service size.


in case You’ve a Fuse Panel Although most homes today have circuit breaker panels with a major circuit breaker, if your house has an older electric service, it may use fuses to control the individual branch circuits. With this instance, there is going to be a main fuse block with an amp rating that identifies the total service size of the home of yours. This main fuse block has a metal handle, and by pulling the handle outward so the block separates from the panel, you shut off power to the whole house. Most homes served by fuse panels have 30-amp or 60-amp service.



In instances that are rare, a house might have 2 main service panels, like a 200 amp and a second 100 amp service. This typically occurs when a house has been updated with a significant expansion, although it is able to also occur during new construction where the planned electrical load is pretty substantial. With this instance, the home’s total electrical service size is actually the combined amperage of the 2 service panels. Nevertheless, where an electrical service has a subpanel that feeds off the main service panel, the subpanel doesn’t add to the total amount of amperage available.


Tips for Planning Electrical Service Size When an electrical contractor computes the necessary size for electric service during brand new construction or perhaps when updating an electronic system, the process involves computing the likely total demand of all the appliances and fixtures, then sizing the electrical service to offer a more comfortable margin. The calculations are fairly complex, so most electricians use a handy calculator tool to properly size the main electrical service.


Generally, 100 service provides energy that is enough for a range, water heater, as well as general lighting and receptacle outlets. In modern construction, 100 amp service is currently installed only where the heating system and most of the heating appliances use gas rather compared to electricity.

200-amp service provides energy that is enough for an electric heating system, electrical appliances, as well as general lighting and receptacle circuits.

In homes that are big, 400 amp services are actually used with very extensive electric heating plus electrical devices and lighting and receptacle circuits.

Leave a Reply

Your email address will not be published. Required fields are marked *