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3 Prong Plugs
Executive Summary: Three prong outlets require a copper wire to be run from the third hole of the outlet to a proper ground. A GFI is not a proper substitute for a good ground. Most surge-arresters can not work with out a ground. Common surge arresters "self sacrifice" when they take a hit. Low priced units do not warn you when they have been used up. A high quality unit that does not need a ground adn be found at www.zeroSurge.com It uses a large capacitor. A.Q.
Sometimes we get asked if we can please ground all the outlets in a home or home office. It sounds like a good idea, but it is not very practical. Let me explain:
Until circa 2004 it was easy to convert two prong outlets to three prong grounded outlets by running a small #12 or #14 bare copper wire to the nearest grounded outlet or cold water pipe. However there were problems. For example a painter or handy-man might think "Let's get rid of this old ugly wire." and remove it. The code was changed to make the results safer and to last longer.
Now the National Electrical Coce or NEC requires the ground wires to be either inside the wall or else large enough to look formidable so as not be confused with something that can be removed at the next paint job. The minimum size for an exposed ground wire is No. 6 copper which is close to the size of a wooden pencil. Additionally, the ground wire can only be grounded to (1) the main panel, (2) a sub panel or (3) the cold water pipe within five feet of where the water pipe first enters the building. For this reason it is fairly impractical to ground ALL the outlets in an old house or even newer buildings due to the time and expense.
Most modern electronic appliance plugs have only two prongs.The few appliances that have a three prong outlet are usually appliance or other "metal boxes" like a refrigerator, freezer, microwave, garage door opener or commercial equipment like you find in restaurant. In those cases, it does make sense to have a grounded plug. It may actually be required. Some new appliances have a label on the cord that states that the warrantee requires the grounded plug outlet. Most of these appliances are found in the kitchen.
If you take a survey of your non-kitchen appliances you will see that very few actually have a three-prong grounded plug. You may discover that there are very few two-prong outlets in the other rooms. Don't be fooled by a three prong power strip that is only being used for two prong plugs. Of course it's not practical to ground a plug for a power strip and then to only use it for two pronged plugs. Two-pronged power strips are available.
Note: Some notebook computers have a three-prong power cord where the ground wire is not actually used as far as I can tell. The cord runs in to a plastic transformer and then via two wires to the computer. Either the manufacturers got a good price on omnipresent three-prong cords or they think it looks better or else I don't know why they use them.
A work-around: One way is to install a GFI or Ground Fault Interrupter. It is ok as long as you attach the little sticker that comes in the box that states "non grounded outlet." Even though the third hole doesn't go any place the electronics in the GFI do provide for life safety but not equipment grounding. This type of GFI conversion is not suitable for a refrigerator or other appliance where the manufacture states that a grounded outlet is required in order for them to honor the warranty.
A few houses built in the 1950s had grounded boxes but they only used two prong outlets at that time. If you're lucky enough to own house of that era, simply changing the two prong outlets to three prong plugs (after testing for a good ground) is a good solution. The code allows us to use one GFI to cover "down stream" outlets and to put in three-prong outlets as long as we put a sticker on each on that says "No Equipment Ground" This sticker comes in the box with each GFI.
(c) 2010 John A. Peters www.brooklineElectric.com 415-239-5393
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