DIY Home Improvement Forum banner
1 - 5 of 5 Posts

· Registered
1,889 Posts
Discussion Starter · #1 ·
....made by GB Instruments, it's called a 'Circuit Alert' tester, battery operated, about the size of a large ballpoint pen.

In any event, I am trying to figure out why this tester "beeps" when I touch a wire leading to a baseboard heater WHOSE 20 AMP CIRCUIT BREAKER HAS BEEN TURNED OFF???

I am thinking of changing a baseboard heater, from a 1500 W to a 1750 W; there is a 20 amp circuit breaker at the main panel, that I have switched off...but before starting the work, as a precaution, I tested the 12/2 wire with my tester pen - and the thing beeps like there's electricity running to the heater??? Huh?

Can anyone explain to me why my pen beeps when the circuit breaker at the panel is turned off? Thanks!

· Super Moderator
11,049 Posts
Never use a pen type tester to ensure the power is off.
They can be set of by static, or the proximity of other wires close to the ones you are testing.
You need a meter to make sure the power is off.

· Idiot Emeritus
1,910 Posts
Non-contact voltage testers are commonly known to pros as 'death sticks'.

They will regularly beep when no voltage is present, and fail to beep when actual (and possibly lethal) voltage is indeed present.

I use a solenoid type voltage tester, commonly known as a 'wiggy'. This type of tester puts a slight load on the circuit and if used correctly it certainly will read actual voltage, but not phantom voltage. A basic standard digital multimeter will read actual voltage as well, but it can be tricked into reading voltage when none is present, because it doesn't load the circuit.


· Banned
17,162 Posts
Works on magnetism/inductance from the electrons flowing through the copper. Mine would go off when I got close to a line that I had switched off, due to it was close to another active circuit. The pen would do a quick beep, then wouldn't do it again.
1 - 5 of 5 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.