Plug-In Electrical Testers, continued
If the neutral is open, a plugged-in tool or appliance should
not work. This presents no danger unless the user attempts to
work on the tool or appliance while it is still plugged in.
Since the hot is still connected, the user could provide a
neutral path and get a severe shock. The same applies inside
the receptacle — turn off the power at the panel before
If you check the receptacle and the neutral is properly
connected, you'll need to trace the wire back toward the panel,
looking for a loose connection or a nail that has cut the wire.
A loose or partially severed wire can cause a fire. Always
leave the power off until you find and fix the problem.
An open hot is
immediately obvious: None of the display lights on the tester
will light. Turn the circuit off as soon as you've finished
making the test; a loose or broken hot can start a fire.
If there is nothing obviously wrong inside the box, you'll
have to look for a loose connection or severed wire somewhere
in the circuit.
Many testers also have a GFCI test button. When
the button is pressed, a simulated ground fault is
placed on the line. A properly working GFCI will
trip (assuming it’s on a grounded circuit).
You can also test GFCI-protected receptacles wired
downstream from a GFCI receptacle (or circuit
breaker). The simulated ground fault at the
downstream receptacle should trip the GFCI
Although GFCI receptacles will work on two-wire
circuits, they can’t be tested with plug-in
testers, which work by creating an actual fault to
ground. On two-wire circuits you have to use the
test button on the GFCI receptacle itself.
Be aware of what these testers cannot test
• False, or “bootleg,” ground:
This is where some idiot has jumped the neutral
onto the ground connection of the receptacle (see
illustration, right). Why? Who knows? It might be
an effort to fool an inspector into thinking a
circuit is grounded when it’s not. This is a
very dangerous connection and can be
lifethreatening. Assuming something is plugged into
that receptacle and turned on, this puts current on
the grounding circuit in parallel with the neutral.
That means anyone using an appliance anywhere on
that branch would be in danger of shock.
• Ground and neutral reversed: This is rare
because most people wiring a receptacle know that
the ground wire is the bare wire. If it should
happen, an appliance plugged into that receptacle
will put current flow through the grounding wire
instead of the neutral. This can endanger anyone
who operates an appliance anywhere on that branch
circuit. (It also endangers an electrician who is
troubleshooting the circuit.)
• Quality of ground: This is a test to verify
that the ground resistance path from the receptacle
to the main panel is not only intact but is also a
low-resistance path. This can only be done with a
more elaborate plug-in tester (see “Advanced
Plug-In Tester,” previous page).
• Any combination of defects: If two of the
tests share the same indicator light — for
example, the open neutral test and the open hot
test — you might think there is only an open
hot when the neutral is also open. Since the power
is off to the receptacle (because of the open hot),
there is no way for the tester to light the
indicator for the open neutral. The solution is to
remedy the open hot, then retest for other
• Check a standard two-prong ungrounded
receptacle: For this, you will need a more
expensive test device, one with a retractable
• Check for voltage drop on the line: Again,
this is a job for the professional tester.
Hot and Ground Reversed
installer would have to be drunk to do this. This could only
happen on a circuit with just one receptacle; otherwise, the
breaker would immediately trip. Assuming the one receptacle,
it's a potentially lethal situation. If an appliance like a
clothes washer or electric drill is plugged in, its frame will
be hot and will shock anyone that touches it.
Hot on Neutral with Open Hot
I’ve never encountered this situation and probably never
will. It’s basically a reversed polarity situation where
the neutral has come loose. Even though the hot is on the
neutral side, there is no return path to complete the circuit.
Appliances won’t work when plugged into a receptacle
wired this way.
Rex Cauldwellowns Little Mountain Electric in Copper