While the phase to phase reading is best for troubleshooting, for safety you test phase conductor to ground.

 

Phase to phase, phase to neutral, and phase to ground.

If you are not doing the above please stay home and let an electrician handle the job.

 

I have seen on the web that some people call a "non-contact tester" a widow maker. How about this scenario?

if you place your Digital Volt-Ohm Meter (DVOM) across the two 120V lines at your air conditioner contactor, and one of those 120V lines is disconnected "broken off" from the outside kill breaker, you would read zero volts.

This is because the voltage potential difference requires a complete circuit.

If one of the lines is open or disconnected, there is no path for the current to flow, resulting in no voltage reading between the two points.

Using a non-contact voltage tester (NCVT) would still indicate the presence of voltage on the live wire, even if one of the 120V lines is disconnected.

Non-contact testers detect the electric field around an energized wire. The Non-contact tester will "see" if it is live, without requiring a complete circuit.

This tool can help alert you to a potentially dangerous live wire, even if the circuit isn't complete, offering an additional layer of safety when working with electrical systems.

Please tell me your thoughts.

on a two pole or polyphase circuit, one SHOULD ALWAYS CHECK FOR POTENTIAL TO GROUND before touching. NEVER bet your life on a NC tester alone.

 

A non-contact tester is just a tool in the toolbox.

Anybody who is completely opposed to using one is just ignorant. On the flip side many people are too reliant on them. Unfortunately both mentioned groups are usually ignorant of how these non-contact testers work. Once you understand how they work you can use your brain to know when to use one.

Again, it's just a tool in the tool box.

 

Non-contact testers detect the electric field around an energized wire. The Non-contact tester will "see" if it is live, without requiring a complete circuit.

Not to be nit picky but your body is completeing the circuit. Current IS flowing.

 

I have seen on the web that some people call a "non-contact tester" a widow maker. How about this scenario?

if you place your Digital Volt-Ohm Meter (DVOM) across the two 120V lines at your air conditioner contactor, and one of those 120V lines is disconnected "broken off" from the outside kill breaker, you would read zero volts.

This is because the voltage potential difference requires a complete circuit.

If one of the lines is open or disconnected, there is no path for the current to flow, resulting in no voltage reading between the two points.

Using a non-contact voltage tester (NCVT) would still indicate the presence of voltage on the live wire, even if one of the 120V lines is disconnected.

Non-contact testers detect the electric field around an energized wire. The Non-contact tester will "see" if it is live, without requiring a complete circuit.

This tool can help alert you to a potentially dangerous live wire, even if the circuit isn't complete, offering an additional layer of safety when working with electrical systems.

Please tell me your thoughts.

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This sites for professionals in the electric field ( hey that’s kind of a pun, never noticed before). None of us are going to say a tick tracer is better than a meter which seems to be what you are going for.

 

This sites for professionals in the electric field ( hey that’s kind of a pun, never noticed before). None of us are going to say a tick tracer is better than a meter which seems to be what you are going for.

No just saying it is an extra precaution.

 

How about this scenario.

I take a non-contact tester and rub it on my arm, it lights up!

Does that mean I'm hot?

Used that on a girlfriend or two.

They weren't impressed.

 

It is just an extra precaution, if a DIY was going to change out his contactor and he just used a dvom, in this case, he would be fooled, don't you agree?

 

Tickers will read any electrical field so you end up with a bunch of false reads. If your a home owner that's fine but after a while in the trade you learn not to trust the light.

Once you learn not to trust it you start to second guess it then one day the ticker is correct and you guessed wrong so you end up getting poked.

It's a tool but it's not a volt meter.

 

I don't mind a false positive. I don't like false negatives.
I use my NCV as a last minute 'did I turn the disconnect back off for the umpteenth time during this troubleshooting session' confirmation. If it lights up then I use something else to confirm.

 

There are ways to measure voltage above 1000 V. The most common way to test for medium voltage is with a noncontact voltage tester. The problem they cause though is they detect voltage fields. Some switchgear cubicles have FR3 (red fiberglass) covers over the energized bus so it sets the thing off. And they won't detect capacitors...the rule is wait 15 minutes. And around shielded cables it can be hit or miss. So we do test, then ground everything so it's not really a factor. But that's energized work and if it's really energized you'll know it when it arcs badly.

There are a couple other ways to do this using voltage dividers. The first is you can use an old school TV flyback transformer teser. This is a small inexpensive device (about $100) that you plug into your meter. It has a clip that MUST go to ground and a probe that is rated up to 28 kV for most of them. Internally it has a 1000:1 ratio of resistors so that 3000 V on the input becomes 3.000 V at the meter. It can do AC or DC.

The other device is a Beiers PD10 or PD25 (10 kV or 25 kV). This one comes with 2 probes suitable for hot stick mounting and a meter on one of them. You just touch two points for a reading. It can do phase to phase or phase to ground. AC only. This one is more of a "utility" meter and to put it politely, it isn't cheap.

At low voltage you are supposed to test all points of potential by the way. So that's not just phase to phase (3 checks) but phase to ground and really whatever you see in the cabinet that is suspect. For insance external devices may be connected to a local isolation relay or to relay or aux contacts that are powered from somewhere else. Quite often it's hard to even identify where this stuff comes from.