Electrical System - Home Inspector Tip

Tip of the Week.

Electrical System

System Overview
The way your house gets its electrical service is from what's called a service drop that comes from your local utility company.  In older communities there are overhead wires that line the street with the wires dedicated to individual homes branching off of the main line.  Newer communities have the wires running underground into the home which makes for a more appealing look in the neighborhood.  Where the service drop wires from the utility end is called the service point.  Here the wires are spliced and become the service entrance wires that go into the home.

Service Size
A home's service size is a measure of the amount of current capacity it can sustain.  Service size includes voltage and ampacity.  Voltage is the maximum electrical energy the house has and ampacity is the amount of current running through the system.  Service size is important to know because houses built, say, 30 to 40 years ago, or more, have smaller service sizes than those built to today's standards.  The standards are ever changing because technology continues to change, providing us with newer appliances, entertainment systems, and the like that require more power.  A house built 40 years ago may have 60 or 100 amps and 120 volts.  For that time period, that was adequate for the load people placed on their electrical systems. 

Today there is newer and more advanced equipment that requires much more power.  With the advent of microwave ovens, home theater systems, multi-zone air conditioner systems, homes today require at least 200 amp service with 240 volts. 

Determining what's in a house
If you're buying a house, it is important to know the service size of the electrical system.  The amps and voltage in a house can be determined in two ways:

•§         In overhead wiring systems where the utility service drop splits off into the service entrance wires, the wiring is usually labeled with the ampacity.

•§         In under ground wiring systems you will have to go to the electrical panel box.  Here you will see where the service entrance cables come into the box and attach to the service panel connections.  The service wiring is usually labeled with the ampacity it carries either at, or in, the service panel.

Service Panel
Modern day service panels can have at most 42 breakers.  This is adequate for most homes.  Larger houses - those that are 4000, sq. ft. and above, for example - may need extra panel boxes known as subpanels to accommodate the work load.  The electrical panel must be rated for the service size of the electrical system.  I.e., if the service is 200 amps, the panel size must also be 200 amps.

Issues with electrical systems

The electrical system in a house is one of the most complex aspects of the home.  Undoubtedly one newsletter cannot cover all of the aspects of an electrical system, so I'll cover a few this week and at a later time I'll cover additional items.

•§         Overhead Wire Height Restrictions

Inspection of an electrical system begins on the outside of the house.  For houses that have overhead wires, there's a conduit called the service mast that contains the wiring that goes from the utility to the home.  The  top of the mast has a service cap that curves downward protecting the wires from rain water.  The service mast is usually attached to the house and is the point at which the service entrance wires connect to the service wires from the utility.  In most jurisdictions the overhead wires leading from the utility pole to the service mast must be a minimum of 18 ft. high at the street.  On the property, the wires must be 10 ft. above walkways and 12 ft. above driveways.

•§         Electrical Panel Location

In single family homes electrical panels are usually found in the basement or on the first level of the home if no basement exists.  The panel should be easily accessible and is not permitted to be in closets, stairwells or bathrooms.  They can however be outside, but must be in a weather-tight enclosure.

•§         Double Tapping

In houses where the owner has decided to add electrical service to additional areas in a home, there have been cases where the person decides to use an existing circuit in the distribution panel instead of adding a new breaker.  This is a dangerous practice that could result in a fire.  In some jurisdictions this is a punishable offense.  If you have decided to add electrical capability to your home and your service panel has the maximum number of circuits, a subpanel can be added to accommodate the additional demands.

•§         GFCI Problems

GFCI stands for ground fault circuit interrupter.  They protect circuits from being overloaded.  GFCI receptacles have a "test" and "reset" button so that the circuit can be tested for proper functionality.  GFCI receptacles are required in areas of a home where a lot of moisture is expected.  Areas such bathrooms, kitchen counters, garages, unfinished basements all require GFCI receptacles.

... and this is your Marquís Home Inspections Tip of the Week

Derrek Hicks
Marquís Home Inspections
PO Box 2699
Germantown, Maryland 20874
240-401-1418 ph
301-528-8503 fax
derrekhicks@marquishomeinspections.com
www.marquishomeinspectionscom