Grounded (3 Prong) -VS-
Non-Grounded (2 Prong) Receptacles.
Anyone who has ever worked on or lived in a home that was built before the Mid 1960’s has seen them, the old “2 prong” non-grounded receptacles.
How many of them have you changed out with new “3 Prong” grounded receptacles in order to accommodate a new appliance or computer?
How many times have you failed a Mechanical inspection due to a receptacle with an “Open Ground”
So what’s the big deal anyway?
An equipment grounding conductor installed in an electrical branch circuit is designed to provide a continuous path to facilitate the movement of electrical current caused by surges and or faults – to earth via the homes grounding system.
If an appliance that has damaged wiring is plugged into a supposed “Grounded” (3 Prong) receptacle, instead following the assumed grounding path back to earth, fault or surge currents could be passed through the user.
By installing a “Grounded” (3 Prong) receptacle on an un-grounded electrical branch circuit, you may facilitate the use an appliance that under the right circumstances could cause serious injury or death to an unsuspecting user.
Since most homes that were built before the Mid 1960’s were wired using an un-grounded electrical system, the use of “2 prong” non-grounded receptacles was all that was required.
Changes to the National Electric Code that started requiring the use of an equipment grounding conductor in all branch circuits and the introduction of sensitive electronic devices into our homes over the last40 years, have driven the need to install Grounded type (3 Prong) receptacles to accommodate the way we live today.
So what’s the right way to do this?
How do you update the outlets in your home, without creating a potential electrocution hazard?
We all know that rewiring an entire home can be very expensive and can potentially cause severe secondary damage to the homes finish.
Fortunately the National Electric Code affords us a few less drastic options.
Article 406 of the 2008 NEC says that only where connection to an equipment grounding conductor is possible shall a Grounded (3 Prong) receptacle be installed, unless one of the following replacement methods are used.
1) A non-grounded (2 Prong) receptacle shall be allowed to be replaced with a Ground Fault Circuit Interrupter (GFCI) receptacle. These receptacles shall be marked ” No Equipment Ground”. This marking is usually done by use of a small sticker placed on the receptacle cover plate.
2) A non-grounded (2 Prong) receptacle shall be allowed to be replaced with a grounded (3 Prong) receptacle, where supplied through a GFCI device. These receptacles shall be marked as ” No Equipment Ground” and “GFCI Protected”. Again this is usually done by use of small stickers placed on the receptacle cover plate.
A GFCI device may be either a circuit breaker or receptacle. GFCI Devices are designed with an internal circuit that measures the amount of electrical current returning on the white- grounded circuit conductor ( or what is often referred to as the “Neutral”), as compared to the amount of current being drawn from the device on the black- ungrounded circuit conductor ( “Hot”). If the amount of current returning varies by more than the amount allowable by safety standards then the GFCI will open, thus cutting the flow of current through the circuit.
It is important to note when employing the use of GFCI protection as outlined in option #2 above, protection may be achieved through the use of either a GFCI receptacle, or a GFCI Breaker.
Depending on the type of electrical service in the home, Fuses or Breakers and the wiring method used when the home was initially wired, it is often more cost effective to install GFCI breakers to protect the entire circuit than it is to spend several hours of labor trying to separate out individual devices for protection.
One thing to keep in mind any time you are installing a GFCI device of any kind, is that the contents of refrigerators and chest freezer can be lost if plugged into a GFCI protected receptacle that trips and is not reset before the contents thaw.
As always every home is different, as is every wiring system. You should always consult a licensed Master Electrician before starting any electrical project.
Article Provided by
Accessible Electric Inc.
Serving the KC Metro Area since 1995