testing grounding system

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fleetfeet

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Old EMT run in a school made me leary of how safe the grounding system was (no grounding conductor, no pigtail from box, etc.) I was convinced that the grounding system wouldn't work, but a co-worker thought it was good. He attempted to short the circuit by touching it to the EMT to test. Is this correct procedure, or possibly a cheap way to test?
 
Re: testing grounding system

You really need an instrument that can read the impedance between the ground pin and grounded circuit conductor.
 
Re: testing grounding system

Originally posted by nec4me:
Were you 2 guys in that movie "Dumb and Dumber"?
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HUH?

Roger
 
Re: testing grounding system

I'm seeking knowledge and guidance. Logically, you'd think touching hot to ground would test the grounding system to a certain extent. However, this is probably not practical because of the danger of not having ground.

I thought this senario was quite routine (i.e. not having a grounding conductor). Rather than assume it has proper grounding, there should be a practical (not expensive) way to test.
 
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You could go to a hardware store and buy one of those outlet testers with the two yellow lights and one red light. If you plug it in and get the right pattern of lights, it gives you a very warm and fuzzy (and false) sense of confidence that the circuit is properly grounded. I say ?false,? because I believe that if someone had connected the grounded (i.e., neutral) wire to the Equipment Grounding Conductor (i.e., bare or green wire), it would show the light pattern for a correct installation.

Actually, I do think there is value in this product. That is because if it gives you a reading that something is wrong, you can have confidence that something really is wrong. You just can?t be as certain that a ?OK? reading means that things really are OK.
 
Re: testing grounding system

FleetFeet I understand the handle now LOL :p
With working around someone using methods like that I would have fleet feet tooooooooooo-
But one thing that could happen is if this conduit is rusted out and just barely making connection and this place is by something combustible you could have a fire :eek: You need a very low impedance meter that reads 1 ohm and below. This is the only sure way to test the grounding and also after de-energizing the circuits lift the neutral and see if it is still has continuity to the grounds This is a good way to check for bootlegged grounds.
 
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I have done alot of work in schools and I have seen the condition of the conduit runs you spoke of. I have also seen alot of Federal Pacific panels in schools. You may know that you could arc weld with Federal Pacific protected conductors before they ever trip. You friend must be a carrer apprentice. He/she could damage sensitive equipment this way, especialy if the ground path is faulty. I have also seen ground faults act as a load rather than tripping the breaker. This also happens when you have an ineffective ground. To answere your question about if it is a cheap way to test for ground. No, it is a dumb way to hurt yourself, someone else or even damage sensitive equipment. I would use the proper equipment or pull a ground.
 
Re: testing grounding system

Originally posted by fleetfeet:
there should be a practical (not expensive) way to test.
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Well actually there is with a little imagination, a calculator, volt meter, and a known load.

In my early years I made a black box so to speak. A aluminum utility box with a resistor, switches, plug-n-cord, and test points for a volt meter. Basically you take the open circuit voltages between P-N, P-G, and N-G. Apply a load between P-N (normal mode), and repeat the voltage measurements. Then place the load between P-G and repeat the measurements. With the measurements you can determine the impedance of each conductor, proper polarity, percentage of voltage drop at full load, and a false ground (boot-leg).

Or you can just buy a Idea Sure test and it does the exact same thing.
 
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I knew an electrician, (I use the term loosely) years ago,that used the "short" method to locate the circuit breaker in a panel that fed a particular circuit. He simply shorted hot to neutral then went to panel to see which breaker was tripped. Dont know if he is still around or not. ;)
 
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I'm still here. Retired now. Never had a problem shorting the hot to neutral or equipment ground in 40 years of being career apprentice.
 
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If by chance the conduit is open then what ? maybe electrocute some one thats touching a grounded item? You might do this for years and be lucky and then again you might retire someone else early.Will you be able to enjoy your life if you kill some little kid or his parents ?

[ October 23, 2004, 10:49 AM: Message edited by: jimwalker ]
 
Re: testing grounding system

If the conduit is grounded like it should be, there is no danger to anyone. If the conduit is not grounded, then I investigate and repair the conduit so there is no danger from a ungrounded couduit. Are kids and their parents hanging on conduit?

If a conduit was not grounded and became energized, then there would be danger to kids and their parents.
 
Re: testing grounding system

Originally posted by derwith:
I'm still here. Retired now. Never had a problem shorting the hot to neutral or equipment ground in 40 years of being career apprentice.
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When I read this I thought you where joking as you said 40 year apprentice.

Originally posted by derwith:
If the conduit is grounded like it should be, there is no danger to anyone. If the conduit is not grounded, then I investigate and repair the conduit so there is no danger from a ungrounded couduit. Are kids and their parents hanging on conduit?

If a conduit was not grounded and became energized, then there would be danger to kids and their parents.
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Now after reading this I understand you where not joking and I see why you stayed an apprentice. :roll:

There is no excuse for intentionally shorting wires out. This is the kind of thing the untrained or unqualified do.

Just what happens if the OCPD fails to open?

How do you explain the resulting damage to the customer?

Try this in a building with GFP protected feeders or service and you may find out how well the emergency lights work. :eek:
 
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What if a kid touches a water fountain (very likely) and it's conduit is part of the non grounded emt.You just killed him.Why ? cause you took the fast way out.What if your not the only man working on the system ?You just killed your helper.I am glad im not working with guys that would do this. :mad: :mad: :mad: :mad:

[ October 23, 2004, 06:14 PM: Message edited by: jimwalker ]
 
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One might exspect that the conduit is likely bonded to building steel several places and a return path is available but this can not be counted on
 
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I myself have noticed that people who have been in the industry and taught by other people who have not had the chance to use the proper method use the 'short to conduit/box' method. It is not too expensive today to purchase the proper meter(s) necessary to make the right test(s).

Yes I agree with the above Posters that this can be deadly and costly and should not be used.

Pierre
 
Re: testing grounding system

There is one other problem with doing this. If this circuit is part of a multiwire circuit (which in a commercial environment it will most likely be) you will cause a high voltage spike to surge through the other side of this circuit which will cause damage to equipment on this circuit.
 
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