Sometimes we get a request to 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. 

 

Most modern electronic appliances have a two prong plugs. The few appliances that have a three prong outlet are usually 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.  Sometimes there's a label on the appliance cord that states the warrantee requires the grounded plug outlet.  Most of these appliances are found in the kitchen.

 

If you take a survey of your appliances to see which actually have three-prong grounded plug cords, you may discover that there are very few.  Don't be fooled by a three prong power strip that is only serving 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 available.

 

A GFI may be suggested as a work around. It is ok as long as yu attach the little sticker that comes in the box that states "non grounded outlet"  A GFI will kill the power instead of killing  you.  It will not provide an equipment ground which may be required by the equipment manufacturer.  An example is the tag on a refrigerator that says "Warrantee is void in a non grounded outlet is used".

 

Until circa 2004 it was easy to convert two prong outlets to three prong grounded outlets by running a small #12 or #14 bare wire to the nearest grounded outlet or cold water pipe,  The code has changed to make the results safer. It was found that some times a painter removed the little ground wire as it was not readily apparent that it served any purpose.

 

Current NEC code requires the ground wires to be either inside the wall or else large enough so as not be confused with something that can be removed at the next paint job. Exposed ground wires have to be at least #4 which is just about the size of common wood pencil.  The ground wire can only be grounded to (1) the panel, (2) a sub panel or (3) the cold water pipe within five feet of where the water pipe first enters the building.

 

(c) 2010 John A. Peters

Rev 0.1 January 31, 2009

Rev 0.2 January 2, 2010