Verifying 'NO VOLTAGE" prior to work.

OKay,

thanks for all the responses to my previous thread "Use of non-contact voltage detector for verifying no voltage present.'"

Now that I've seen the answers, and had a little time to review things at work, I have re-phrased the question as follows:

Does NFPA 70E allow for non-contact voltage detectors to verify no voltage prior to working on exposed parts?

And, a follow-up, does a LED voltage detector that is directly attached to the bus/phases/etc. and which shows (manufacturer's statements) phase-to-phase and phase-to-ground indication (not a value, just an LED "on" means voltage present) qualify as a "contact" voltage test to verify no-voltage present?

This should "spark" a few responses.
Thanks!
 

GoldDigger

Moderator
Staff member
And, a follow-up, does a LED voltage detector that is directly attached to the bus/phases/etc. and which shows (manufacturer's statements) phase-to-phase and phase-to-ground indication (not a value, just an LED "on" means voltage present) qualify as a "contact" voltage test to verify no-voltage present?

This should "spark" a few responses.
Thanks!
I would have to know what the actual voltage threshold of the device was to decide where it was appropriate to use it.
Knowing that a wire does not have more than 40 volts AC on it may persuade me that it is safe, in terms of shock hazard, to touch the wiring, but if it still has 12 volts DC on it from a car battery I would still want to be very careful about shorting it out.
 
I would have to know what the actual voltage threshold of the device was to decide where it was appropriate to use it.
Knowing that a wire does not have more than 40 volts AC on it may persuade me that it is safe, in terms of shock hazard, to touch the wiring, but if it still has 12 volts DC on it from a car battery I would still want to be very careful about shorting it out.
Sorry, left out another piece of important information! - the voltage to be verified "dead" is 480VAC, three phase, on a 60A circuit.
 

Luketrician

Senior Member
Location
West Pawtucket
Not sure what NFPA says.

At our plant, all Live dead Live checks 480VAC and below are done with a V.O.M that is within calibration.

Check a known live source..then check the device/component to be worked on (that is supposed to be tagged out)...Then back to the known live source to verify proper meter operation.

Medium voltages and up are done with glow/sticks and prox testers.
 

cornbread

Senior Member
In my huble opinion a NO contact detector doe not meet the intent of 70E.

120.5 Use an adequately rated voltage detector... phase to phase .. & phase to ground.. Before and after each test, determine that the voltage detector is operating satisfactorily.

Will the "in door" voltage detector meet this requirement of testing after each test? Again my humble opinion is no it does not.

With that said I've seen folks use a cheap ..cheap meter..one i would not use to test a 1.5 volt batterty .... to measure 480V.
 
Just a couple of comments regarding the permanently installed voltage indicators:


  • Sites generally justify permanently installed voltage indicators for isolation verification prior to non-electrical works eg greasing bearings, tightening belts etc. In addition it can be more reliable than Try Start!
  • Number of isolations for non electrical work normally exceeds number of isolations for electrical work
  • Knowing that the disconnect has opened the power circuit correctly (permanently installed voltage indicator reports this) provides for a safer entry into the panel for sparkys to perform contact voltage tests. Some engineers believe that this may reduce arc flash ppe requirements

Aside from the above, contact testing before touching before electrical work was flogged into me at an early age.
 

RichB

Senior Member
Location
Tacoma, Wa
Not understanding all the confusion on this topic--IIRC OSHA says to check phase-to-phase and phase-to-ground---IMHO that can only be done with a meter that has leads that are touched(connected) either phase-to-phase or phase-to-ground, therefore a non contact tester does NOT meet the requirement and cannot be used for verification.
 
I suspect RichB, the confusion relates to verification for the two different types of work 1. electrical work and 2. non-electrical work.

In Australia, and I am pretty sure the US also, in the case of 1. electrical work, contact testing is mandatory. In the case of 2. non-electrical work, contact testing is not mandatory.
 

RichB

Senior Member
Location
Tacoma, Wa
I suspect RichB, the confusion relates to verification for the two different types of work 1. electrical work and 2. non-electrical work.

In Australia, and I am pretty sure the US also, in the case of 1. electrical work, contact testing is mandatory. In the case of 2. non-electrical work, contact testing is not mandatory.
Maybe--however the OP asked about no volt verification prior to work and 70E is quite specific on how to test for voltage and the procedure is as follows:


--Check a known live source ensuring the device works--then check the circuit in question,,,and you shall chec phase-to-phase and phase-to-ground then recheck on a known live circuit--this cannot be done with a light stick nor can it be done with an installed LED voltage detector--Simple and straight forward--you must comply with the "directions given" in 70E and these cannot be done without using a contact tester--no arguments and no discussion will change that fact
 

zog

Senior Member
Location
Charlotte, NC
Maybe--however the OP asked about no volt verification prior to work and 70E is quite specific on how to test for voltage and the procedure is as follows:


--Check a known live source ensuring the device works--then check the circuit in question,,,and you shall chec phase-to-phase and phase-to-ground then recheck on a known live circuit--this cannot be done with a light stick nor can it be done with an installed LED voltage detector--Simple and straight forward--you must comply with the "directions given" in 70E and these cannot be done without using a contact tester--no arguments and no discussion will change that fact
Agree 100%
 
No arguments from me either. Just making a suggestion as to the reason for permanent voltage indicators and how confusion may arise in the mind of a sparky given their wide spread use. As you have suggested NFPA is pretty clear though.

Caution does need to be exercised even when performing a contact voltage test as it can be misleading in some circumstances. The test should be performed immediately at the load side of the locked isolation point in addition to the point in the installation where the electrical work is being performed.
 

GoldDigger

Moderator
Staff member
The test should be performed immediately at the load side of the locked isolation point in addition to the point in the installation where the electrical work is being performed.
Your reasoning being that there could be an intermediate disconnect which happens to be open in which case you would not measure voltage at the load or point of work even if the LOTO disconnect is not actually open because of a malfunction?
 
Your reasoning being that there could be an intermediate disconnect which happens to be open in which case you would not measure voltage at the load or point of work even if the LOTO disconnect is not actually open because of a malfunction?
Could not have said it better myself GoldDigger.

If the LOTO disconnect is faulty, and there is an intermediate disconnect that is open at the time of the voltage test at the load, the voltage test at the load is inconclusive and places the worker in danger. If you consider the case where the intermediate disconnect is a contactor and the LOTO disconnect is a CB inside an MCC and the load is a terminal box at a motor this arrangement is very common. All you need is a faulty CB and the contactor engages because its under auto control from somewhere and bingo the sparky gets fried. Establishing facilities to address this situation is challenging but doable.

The message is that just because you did a voltage test at the point of work don't think that you are safe!
 

GoldDigger

Moderator
Staff member
Establishing facilities to address this situation is challenging but doable.
Like providing voltage test points at large CBs so that you do not have to either put on PPE and open the CB bucket or figure out where the contactor is and check the line side there?

Sounds like this will be vigorously discussed for quite awhile. :)
 
Like providing voltage test points at large CBs so that you do not have to either put on PPE and open the CB bucket or figure out where the contactor is and check the line side there?

Sounds like this will be vigorously discussed for quite awhile. :)
Sounds like this is territory familiar to you as well GoldDigger!

Of course doing voltage tests at CBs inside MCCs introduces its own dangers like you have suggested. So too does test points on the outside of enclosures. This is one area where a permanently installed voltage indicator maybe worthwhile. We have installed http://www.redbusbar.com/shop/Voltage-Indicator-LEDs/ in the past as the low tech permanently installed voltage indicators introduce new problems.
 

RichB

Senior Member
Location
Tacoma, Wa
I have always been rather "lucky" in that everywhere I have worked we have always been able to test at the load side of the point of LOTO--Including MCCs--However comma--this was in the days before arc flash and corresponding PPE

I learned LOTO in the Navy-except it was just Tag Out there--but it worked!! And I carried that over into civilian life and try to impress on our sparkies and new hires the importance of it--

I teach a short safety class to all the new hires and I start it out simply by saying "The following videos contain graphic material and you may wish to leave the room for a few minutes"--:huh:--nobody ever does--then I show the one of the guy on the train in India followed by the arc flash that blows the 3 guys out of the cabinet.--Then I ask "Have I got your undivided attention?" The half hour talk then goes really well and everybody pays attention. Works fine!
 
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