Why are two prong outlets written up as unsafe by the Inspector?

Have you ever wondered why the Home Inspector writes in the report that those two prong outlets in older homes are a safety issue?  Read on for important information on the safety of your family and you.

[tab: The Issues]

Over the years our use of electrical devices has grown, changed, and so have the devices themselves.  Along with this so has our knowledge for the safety of people using those devices.  Older homes display the lack of knowledge for the safety issues of electrical appliances.  Many of these older homes still contain the older two prong outlets that were never thought to be unsafe, and the safety reasons will be discussed here.  For those of you reading that have a more in depth knowledge of electrical theory please just bite your tongues as the descriptions here are an attempt to be as non-technical as possible to help those that do not have your background and training.

Two prong outlet next to three prong outlet

An older two prong outlet next to the newer three prong outlet (Click image for larger view)

This picture displays the newer three prong electrical outlet found in most homes today along side of the older two prong outlet.  Older outlets did not contain the third prong that allowed an electrical device to access the “ground wire” (called the “equipment grounding conductor” or EGC for short) displayed in the picture.  Under normal operation of any electrical device the current coming from the breaker panel supplying the outlet would enter the outlet from the “hot” connection, flow through your electrical device, and back to the breaker through the “neutral” wire.  The EGC wire is connected to the equipment grounding point of an electrical device through the third prong added to newer outlets.  The equipment grounding point is usually a point on any external metal chassis for the device such as the exterior metal cabinet of a washing machine, dryer, light fixture, etc.  Internal to the electrical device any metallic parts that are not intended to carry operational current (non-energized parts) are connected together (bonded to each other) to provide a safety path to the EGC wire.

The EGC wire would never have current flowing in it unless a fault condition occurred in the electrical device that caused current to be applied to the components not intended to be energized.  The fault condition could be a damaged and/or shorted wire that touches a non-energized part, moistue (water) entering the device which bridges across from an energized part to a non-energized part, as well as other potential conditions.  If a fault occurs in the electrical device there is a possibility it could energize metal parts of the device that a person could touch.  That would result in a potentially lethal shock to the person touching the device.  With the EGC connection any fault current is immediately drained off, under normal conditions, before it can become a danger to people.

As you can see with older two prong outlets the EGC connection was typically not available.  In addition many older wiring types did not even have a third wire (conductor) that could be used for the EGC.  When older homes were wired with three conductor cables, and two prong outlets, the third conductor was either not used or was attached to the outlets metal body.  With three conductor cables one of the first solutions to this, which is no longer considered acceptable, was to use adapters from two prong to three prong and with an additional wire on the adapter.  That wire was then connected to the outlet faceplate’s screw in the expectation that the screw would be connected to the outlet’s metal body and the EGC wire.

With two conductor cables and circuit breakers the concept of protection was the breaker or fuse itself.  It was thought that any fault on the equipment would trip the breaker or blow the fuse in enough time to safely protect anyone in the event of a equipment fault condition.  Unfortunately the amount of electrical current needed to kill a person is a lot less than what it takes to trip a breaker or blow a fuse.  You can compare the two using a bucket of water as an analogy.  To trip the breaker/blow the fuse would take a whole bucket of water.  However to kill a person takes considerable less than one drop of that water in the bucket.

So now you have an understanding of why the two prong outlets in your home are being flagged as a safety issue on an Inspector’s report.  Part of our job as an Inspector is to identify and note safety deficiencies for our clients so that they understand the potentials when they purchase or sell that home.  So what can be done to correct this issue?  Read on to the next tab to learn of the solutions.

[tab: The Solutions]

The solutions to this issue range from doing nothing but knowing the issue is there, all the way up to rewiring the home to include three conductor electrical cabling and replacing the two prong outlets with proper three prong outlets.  Obviously doing nothing is the least costly action in terms of dollars and cents.  However it is a very big risk you take now that you know what the potentials are for harm!

The first thing that should be done though is to determine if two or three conductor electrical cabling was used from the main breaker box to the outlets and devices.  An electrician can remove the dead front cover on the breaker box and sample outlets and switches to see if a third conductor was available and run to each outlet/device.  With older two prong outlets when the EGC wire was run to them they were tied off on the metallic outlet body.  If this is the case then all that is generally needed is to replace the two prong outlets with newer three prong outlets and properly wire with the three conductor existing electrical cable.

If there was only two conductor electrical cabling run to outlets then one lesser expensive solution has been to replace the first outlet serviced by each circuit breaker in the main panel with a Ground Fault Circuit Interruptor (GFCI), or replace the breaker itself with a GFCI capable breaker.  Then you would replace every outlet in the rest of the circuit with three prong outlets.  There are issues with using this method though that need to be understood.

  1. GFCI devices can fail to operate due to a faulty or defective GFCI outlet.  Obviously you most likely would not know this until a fault condition occurred and you were exposed to a dangerous current.
  2. Even if the GFCI unit was fully functional there are conditions where it might well not detect an issue and deactivate the circuit.  You would then be exposed to dangerous currents.
  3. If your outlets are on a separate breaker than the lights or other devices then you would need to protect them with a GFCI capable breaker in the panel.
  4. Larger Amperage GFCI breakers are available for protecting items such as drier circuits, etc., but these are very expensive devices and are subject to inadvertent tripping during normal operations.
  5. There are some locations where you do not want to take the chance that a GFCI inadvertently trips and goes unnoticed for appreciable amount of times.  For example in some older wiring jobs the electrician might not have placed the refrigerator in the kitchen on its own feed and instead added it to the kitchen counter outlet feed.  If the GFCI were to trip inadvertently, and was not caught for an extended period, then the contents of the refrigerator might well be spoiled when it is finally discovered.

If two conductor electrical cabling was used one solution is to add the EGC wire run from the main breaker panel to the first outlet/device on a branch circuit, and then daisy chain it to the remaining outlet/devices on the branch circuit.  This option does require extensive labor to perform and should potentially be only considered last.  One reason for this is that the existing two conductor electrical cabling is most likely very old to begin with.  If you are going to pay the extra labor then you might as well consider paying a little additional and having all new wiring run.  These methods can be expensive and should be approached only after obtaining a full electrical system review and estimates from a properly licensed Electrician.

Most people take actions between these extremes until such time as a full rewire is required for other issues.  It is important though that you consider a full review of your electrical system by a licensed electrician.  If you are purchasing the home the electrician can give you dollar estimates for each of these options that might help you make a better purchase decision.

[tab: Links and References]

Consumer Product Safety Commission – Electrical Receptacle Outlets

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