Seattle Home Inspector's Blog

too technical,

unrelated to what AR is all about,

downright dangerous,

and/or "over-the-top,"----I want to do it anyway.  It is primarily for all the Inspectors in the AR community.  This is not one of those, "go-out-and-buy-some-test-equipment-and-try-this-at-home-type-blogs."

     It has to do with un-grounded wiring in homes.

     Sometimes homes have grounded-type wires run throughout the home, but the ground wire is either not connected to the devices (receptacles, switches, light fixtures etc), or the wire just simply isn't used---or even possibly disconnected somewhere.  Homes wired in the early 60's often have this condition.  This was when they first started manufacturing house wiring that included a ground wire, but there was no requirement to actually "use" the wire. 

     We will often see these ground wires just run back out through the back of the boxes where they are either twisted together and wire-nutted together, or they are merely cut off.  Sometimes they were attached to the metal boxes sometimes they were not.  We might see these boxes in unfinished basements or other partially finished areas of the home.  Here are a couple of examples.

     This becomes a problem for the inspector because it is difficult to check for reversed polarity of two-prong receptacles when the home has been wired this way.  Both slots will read hot.  In fact the entire area around the receptacle within 6"-8" of the receptacle might read "hot" with a voltage tester----we call this "Phantom Voltage" or "Induced Voltage."  (I have written a couple of other blogs on this topic which might be of interest to those of you that have read this far in this one.) 

     This Phantom Voltage is high enough to set off a 90-volt "tick-tracer" (voltage indicator).  The voltage will actually be the same as whatever the voltage of the circuit is.  Because it is an induced voltage there is no actual amperage present so shocks are not an issue.  For the inspector, "CONFUSION" is the issue, because of how all this induced current prevents testing of the device for polarity. 

     The following pictures demonstrate how the many parts of the receptacle and the surrounding wall test as "hot" with the voltage indicator.

   Note that in the next picture, on the left, even the metal screw that holds the cover plate in place reads as "hot."  Simply touching the metal screw with one's finger is enough to "cancel" the Phantom voltage allowing the inspector to use the tester normally to check for proper polarity of the receptacle.