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Basic Electrical Tests using a Wiggy®
What's a Wiggy? This is!
This is an
excerpt from one of my advanced electrical courses for home and commercial
building inspectors. I have modified it slightly for this brief tutorial.
George
Wells,
BS Electrical Engineering, MBA, CMI,
Licensed Electrical/General Contractor, Licensed
Master Electrician
©1992-2011
The
venerable Wiggy®
is perhaps the most versatile electrical tester in the Electrician's, Home
Inspector's, or electrical Technician's arsenal. Almost any routine
test you need to perform can be performed with a Wiggy. The Wiggy can do
the work of a multitude of other testers and it can usually do them better!
  
When using the Wiggy, you will quickly learn the feel of 120VAC, 240VAC, 480VAC,
and DC Voltages. AC Voltages will vibrate slightly and DC will have a
distinctive SNAP of the plunger with no lingering vibration. You will
rarely need to look at the gauge once you learn the feel of each voltage.
You
will need to look at the indicator under the bezel at the top of the Wiggy to
determine the Polarity of a DC Voltage. The Polarity indicator flips to
Red or Black depending on the Polarity. The Polarity indicator will tell
you that the direction of flow is from Red To Black or from Black to Red.
Here are instructions for performing some common tests:
Receptacle Initial wiring
check
BLACK in the SHORT slot RED in
the LONG slot
- should read 120V. If it reads 0V, we already know that we have a
problem. It is probably a disconnected wire. Plunger actuation
should feel strong and solid
- If it reads 240V, the Grounded (a.k.a. Neutral) conductor has been lost and
the receptacle is on a multi-wire circuit. This is a
VERY DANGEROUS condition! You will be
able to feel the 240V in the plunger actuation.
Note: As an electrical
contractor I never installed shared neutral circuits for this reason! They
are legal but when they fail - Watch out!
Receptacle Reverse Polarity
check
BLACK in the SHORT slot and RED
in the Grounding hole
- should read 120V. If not, the Polarity is Reversed.
BLACK in the LONG slot and RED
in the Grounding hole
- should read 0V. If not, the Polarity is Reversed.
Receptacle Open Ground check
BLACK in the SHORT slot and RED
in the Grounding hole
- should read 120V. If 0V, the GROUND is OPEN.
BLACK in the LONG slot and RED
in the Grounding hole
- should read 0V. If not, the Polarity is Reversed.
GFCI Receptacle test
BLACK in the SHORT slot and in
RED Grounding hole
- should TRIP. If it doesn't trip, there is a PROBLEM with the
GFCI.
BLACK in the LONG slot and in
RED Grounding hole
- should read 0V and should NOT TRIP. If it does TRIP, there is a
PROBLEM with the GFCI.
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