Overhead Electrical Service

The Overhead Electrical Service Entrance is where the wires from the electric utility enter your home. They come from a pole near the home.

Parts of an Overhead Service Entrance

There are several parts to the overhead service entrance. Knowing what they are will help you understand the various defects. The parts are:

  1. Service Drop or Service Wires (Service Laterals if underground) – wires running from the utility pole to the home
  2. Mast – this is a stiff metal conduit usually sticking up out of the electrical meter box. It has a mast head on top where the service drop wires enter the mast. It is only used if service comes from overhead.
  3. Mast Head – this is a cap on top of the mast that helps keep water out of the mast.
  4. Splices – this is where wires from the electrical service company attach to the wires that enter your home
  5. Drip Loops – Wires entering the mast head are directed down to form a loop so that water runs down to the bottom of the loop and drips off instead of running down the wire and into the mast.

Common Defects

Bare Wires at Mast Head

Bare wires (conductors) at the mast head are dangerous. See the exception below. If you touch them you may be shocked and potentially killed. These wires have no device to limit the flow of electricity. So if you touch them a lot of electricity may flow through your body! Not good!!! This usually happens because the insulation over the wires has deteriorated from sun exposure. This usually doesn’t happen because wires with UV (sunlight) protected insulation are supposed to be used. So if there are wires exposed, the installer likely used the wrong type of wire. If you find bare wires, or cables with deteriorating insulation, near your mast head, contact an electrician for further evaluation.

Now the exception to this is that there is a bare cable that supports the weight of the power lines running to your home. It’s connected to an insulated wire that goes into the mast head. This is the ‘neutral’ wire. It is grounded. Which means that it is physically connected to a grounding rod at the home. In the electrical panel all the neutral wires (ones with white insulation) are connected to this neutral wire. Note that the neutral wire that passes into the mast head should not have any deteriorating insulation on it.

Unprotected Wire or Cable from Service Entrance to Meter Box or Main Panel

On older homes, generally built in the 1960’s and earlier, they used to run a sheathed cable from the service entrance wires to the meter or main panel. If you have a cable like this, inspect it carefully for wear, cuts, exposed wire, etc. If any of these are seen this cable should be replaced by an electrician. Otherwise these cables are considered ok and don’t need to be replaced.

Now there may be good reasons to replace it such as worry about it being struck or damaged somehow. Or if you are replacing the main panel or meter box, I would go ahead and replace this cable with one that is inside a metal conduit. In fact, it will probably be required by code.

Drip Loops Missing

A drip loop isn’t a separate device in the service entrance. It’s a way of bending the wires that come out of the mast head such that water runs down away from the mast head instead of toward it. Drip loops just outside where the wires enter the mast head help keep water out of the mast and hence the main panel or meter box. Drip loops also provide some slack in the wire in the event that something securing the mast or cables to the building pulls loose.

Mast Loose

The mast that supports the wires from the power company should always be securely fastened to the home. If brackets that secure it to the home are loose, this should be repaired.

Overhead Wires Too Close to Various Objects and Surfaces

Overhead electrical wires are required to be a certain distance from various objects and surfaces. Here are some of the requirements as of this writing:

  • 12 feet above a driveway
  • 10 feet above a walkway or yard
  • 10 feet above a deck or balcony
  • 18 feet above a street or parking lot
  • 8 feet above a low pitch roof
  • 3 feet above a high pitch roof
  • and more

For more detailed information check with your local code authority, consult the code yourself, or use one of the many reference books that are a lot easier to read than the codes themselves. One reference book I like is Code Check Complete – 2nd Edition.

Now before I finish this subject, what about wires running through tree limbs? This can be a problem. Trees can rub the insulation off the wires which can pose a shock hazard. When trees sway in the wind (and we get 100 mile an hour gusts where I live) the wires can get stretched and pulled away from the house or pole, etc. So electrical wires should be kept away from tree limbs.

Supports Pulled Out

Service entrance wires are usually either fastened to the mast with a clamp or to a device screwed into the side of the house. Sometimes these devices get pulled away from the home or break. If this happens the the power lines end up supporting themselves. This is problematic because it stresses the connections between the overhead wire and the wires at the home or pole. Neither is good. This should always be corrected as soon as possible.

Masthead Missing

Strange things happen sometimes! This is one of them. Once in a great while I will see a missing masthead. This should be fixed ASAP as rain and snow can get down into the mast and cause problems in the meter box or main panel below.

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