Non-contact voltage detector

What are your thoughts on using a non-contact voltage detector for LOTO of low-voltage systems (600 V)? I have heard both sides of the issue. I used to think that I would not allow them for LOTO. Then I worked at a paper mill that required non-contact to reduce the chance of an arc flash. For eight years and counting they have never had a failure to detect. So I changed my mind.

Now I work for a new company and we're implementing a brand new electrical safety program. I'm debating whether to require non-contact voltage detectors for LOTO. Currently they use Fluke multimeters with all sorts of settings. It's too easy for an inexperienced worker to get it wrong. I'm not trying to get away from arc flash PPE. I do believe that non-contact detectors are safe and reduce the chance of an arc flash.

I know some people who would never trust a non-contact tester. I understand that. I also know that electricians always flick the back of their hand on the bus bar after it is locked out, "just in case". Not a bad practice.

We use non-contact detectors on medium voltage equipment, why would we not use it on 120-600 VAC, for LOTO?

Are there any hard reasons not to use non-contact detectors?

For general motor LOTO you do not have to test voltage. The correct method is to first verify the motor runs by pressing jog/start button, then open disconnect and lockout, then again push jog/start to verify motor does not run. This safeguards that you locked out the right motor.

If you are going to perform electric work, like on a panel, then you would need to test voltage. I don't think most electricians would want to go by the non-contact tester. Although in reality there really isn't any difference, I mean the meter 'feels' better in that you see it display zero and assume its working properly. In both cases you should test on a known source to verify meter funtion. I think if you find a high quality tester and vet it in multiple conditions for some time, ie use both contact and noncontact, you will develope confidence in the device.

Read the instructions of your detector. It says something like "Warning, do not use on 3 phase systems where the conductors are close together". The feilds can cancel each other out and give a false negative, if the conductors are close together, like a motor peckerhead.

Good points Haze

I did have a non-contact fail me once. Not a pleasent surprise. As mascott pointed out, I've also seen a multimeter explode in a guys hand because he had it set wrong. The old fashoned wiggy is still a good choice to check voltage.

If it is CAT III rated, old wiggys are not.

My Fluke non-contact voltage detector (1AC-A1-II) advertises a voltage detection from 90VAC to 1000VAC (CAT IV). I understand this as it does not detect a voltage lower than 90VAC.

Q1: NFPA 70E asks to verify the deenergized state of each phase conductor or circuit part (120.1(5)). Less than 90VAC is not a deenergized state. Do other non-contact voltage detectors have a broader detection range?

Q2: In the same article, the second sentence says "Test each phase conductor or circuit part both phase-to-phase and phase-to-ground." A non-contact voltage detector (wand-like) doesn't do that, it only detects the electrical field in the vicinity of it's nose. So, can it be used? What about MV non-contact voltage detectors?

Q3: What about the presence of DC on an AC nominal line? Would a TRMS voltage tester better indicate the energized state of such a line?