One device that I find ever so handy, and I had been resistant to purchasing it in the first place, is the Suretest circuit tester. Sure, you do not need the Suretest to determine polarity of AC circuits, a $9.00 tester will do that. But the good thing about the Suretest is that it does a more in depth analysis of the circuit than a $9.00 device. It will not only check polarity but also voltage drop and a myriad of esoteric things. I like it because it looks for bootleg grounds.
A proper modern circuit has what we will describe as the hot side, the neutral and the equipment ground. Sometimes, with an old two-wire system, people will "jumper" the neutral to the equipment ground terminal at a receptacle. With a simple circuit tester, the receptacle tests at A-OK. It is fooled.
Suretest, which measures the impedance of the circuit, will tell you that the ground is not real -- It is a bootleg. That might sound like overkill, for an inspector to know that, but it is valuable when an inspector knows that knob and tube wiring had been in place at one time or another.
Knob and tube was a two conductor system so, if the receptacles are showing a real ground, no bootleg, it hints that knob and tube has been replaced. I will, in such situations, test every receptacle in the home. Based on what I see in the attic, the crawl space and on the face of the Suretest, I have a good idea of whether or not there is knob and tube that is still active.
It is not possible for an inspector to definitively declare that knob and tube is gone. That takes an electrician. But the inspector can supply very good information. Sometimes, when wiring is upgraded, they replace knob and tube at receptacles but leave it connected to ceiling lights. That would not be detected by the Suretest, as it plugs into receptacles, but this meter sure gives an inspector an advantage over the inspector who has less sophisticated equipment. The photo below was taken at an old knob and tube system, sellers said that wiring had all been replaced. Nope, neutral was jumpered to the equipment ground at some receptacles. That was verified by removing the cover and looking at the wiring to the receptacle. Caught in the act!
While not every home inspector will carry a Suretest (many do) any home inspector who says that he or she has so much background and experience that basic testing tools are not required is foolish or boasting. Don't let that person fool you or your clients.
Steven L. Smith
Bellingham WA Home Inspections
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