Ungrounded VS Grounded Receptacles
What’s the Difference?
Many times over any given year I get into discussions concerning the outlets in the home I am inspecting. To start with I will go over the basics of the old and new.
First of all I am a Licensed Home Inspector with the State of Indiana; however, I always refer my clients to consult with a licensed Electrician for any electrical work and advice on electrical systems.
Homes built prior to the early 1960’s were commonly wired with a 2 wire system, which is missing the modern third wire needed for the equipment ground wire. The first call for grounded receptacles in residential construction I believe dates back to around 1951 when the NEC (National Electric Code) required laundry areas to have grounded receptacles. Devices and locations have been added over the years until the grounded system is a requirement throughout the home.
Electrical devices that can be used with non-grounded receptacles are: lamps, radios, power adapters, toasters, vacuum cleaners and any item that the cord does not have the round third prong.
Electrical devices that require a ground receptacle (equipment ground) are: high end appliances, computers, TV’s, stereo equipment, power tools, surge protector strips and any other electrical device with the cord having the third prong.
Adapters are available that allow for a device using three prong/ground to be used in a two slot receptacle. The adapters are inserted into a two prong receptacle and then the adapter is secured to the receptacle’s center screw of the cover plate. For these to be effective, the grounding of the receptacle body and box is required.
Homes built prior to 1960 most likely will have two prong receptacles, unless they have been updated. Most homes, however, have gone through some form of modernizing/upgrading of the electrical system within the home.
A non-Grounded Outlet is the most common defect found in most homes where the two prong outlet is replaced with a three prong outlet. When the replacement is correct, the receptacle provides an equipment ground using the round hole in the receptacle. Incorrectly installed, the ground is not present; commonly referred to as an open ground. This will not provide an equipment ground and high end equipment, computers, TV’s and other sensitive equipment should not be used on this receptacle with an open ground.
In the event that a high end device such as a computer is plugged into an ungrounded receptacle, the performance of the device may never be affected or problems detected. However, the device can be damaged without warning at any time from static electricity that has no way of being discharged as well as another source of voltage coming in contact such as lightning. This can originate from both internal and external sources. The idea of the ground is to trip the breaker preventing damage to the device or electrical shock to the user. If the device is not properly grounded, and any number of events occurs, the device may be damaged beyond repair. Many manufacturers state in their warranties that using this device with an ungrounded outlet will void the warranty.
Also keep in mind that a surge protector used at an ungrounded outlet is nothing more than a glorified extension cord, and provides a false sense of protection. Using an adapter with the metal spade secured under the cover center screw also is not a ground unless the box is grounded and you confirm it with a tester. These adapters should not be used as a permanent option for grounding.
A Grounded Outlet
When three prong receptacles with open grounds are found and a two wire system is present, the National Standards currently allows the following methods to be used to resolve the problem:
A) Install an equipment ground. (recommended for high end equipment).
B) Provide GFCI protection for the receptacle (either at the receptacle or upstream of the receptacle) and the receptacle are to be marked “No Equipment Ground”. This method does not provide equipment ground.
C) Replace the existing three hole receptacle with a two hole non grounded receptacle.
Polarized plugs have two different sized slots; the neutral is the larger slot, which allows for a device to be plugged in, in only one way to insure correct polarity. Reversed polarity is when the common and hot wires are reversed on the receptacle; when this occurs the large blade receptacle is now hot rather than neutral (this applies to both grounded and ungrounded systems). A good example of this is when a lamp is plugged in with polarity reversed; the exterior metal light bulb socket is “hot” at all times. In this instance when changing the bulb or touching the exterior of the socket the individual can be shocked. Reverse polarity is a safety issue and can also cause problems with high end appliances. Reverse polarity is usually simple to repair. Often times, if multiple receptacles check for reverse polarity it is not uncommon for only one wiring termination to be incorrect. This would still require further investigation by a qualified electrician.
Ground Fault Circuit Interrupters (GFCI’s) are intended to protect the individuals using an electrical device particularly in a wet area. GFCI’s are available as circuit breakers located with the breaker panel and as a receptacle. Most home owners are familiar with these as the receptacle with the little buttons (test and reset buttons) that seem to always trip when using the hair dryer.
GFCI Outlet. The GFCI provides protection to the user and is tripped by sensing current leak/imbalance in turn shutting of the power to the electrical device. The GFCI does not trip by detection of too much amperage like a circuit breaker, and in turn, a standard breaker does not trip under the same reasons that a GFCI would trip.
GFCI’s are a safety item and provides protection from electrical shock and potential electrocution. The GFCI’s are intended to be tested by the homeowner once a month to insure function. GFCI’s can be installed on both a two wire system without a ground and a conventional three wire system.
GFCI protection is required by current standards in various areas, and the following is a partial list of when and where they were required:
1971 exterior receptacles and swimming pool areas, 1975 Bathrooms, 1978 Garages, 1981 Whirlpools and tubs, 1987 Kitchens within 6 ft. of the sink and basements, 1990 unfinished basements and crawl spaces, 1993 wet bar sinks, 1996 all kitchen counter receptacles, dedicated bathroom circuits, all outdoor receptacles and electric car chargers.
In the event that a GFCI does not function properly and cut the power when the test button is pushed, the GFCI should be replaced for safety reasons. In older homes where GFCI’s are not present, I recommend that GFCI’s be installed for the safety they provide, and would be considered an improvement to the property and a Grandfathered safety upgrade.
A common nightlight is often used to test these GFCI outlets for function. A three bulb receptacle tester that Inspectors use can also be purchased to determine if the receptacle is wired properly. These can be purchased from any home store. The use of this device alone is not a replacement of the services of a qualified electrician.
-Jeff Gainey ACI