Check my answer ...

[Charlie Bob]

I was talking to this older electrician one time, he never heard of a megger before, he has about 25 years experience he said. So he was quick to descredit the use of it.
Ater i explain the adventages and use of it, he asked me: " well, the insulation is stripped at every receptacle and device, so how would the megger readings be effective if so?"

Here's what i said:
"you megger between H-G,N-G,H-N(if you are sure there's no loads downstream), so since you are checking for any leakeage between the conductors insulation, at the receptacle or device the sonductor stripped ends on a terminal, which is away from the other conductor terminal your meggering."

I was just thinking about that now.
Does this answer sound good to you all?
Thanks.

 

[augie47]

Sounds good. Air makes a good insulator. Where the conductor is stripped it is insulated from its surroundings by free air. Tell him you are measuring the resistance of free air :grin:

 

[Charlie Bob]

Sounds good. Air makes a good insulator. Where the conductor is stripped it is insulated from its surroundings by free air. Tell him you are measuring the resistance of free air :grin:

Thanks Augie.

 

[Buck Parrish]

I was talking to this older electrician one time, he never heard of a megger before, he has about 25 years experience he said. So he was quick to descredit the use of it.
Ater i explain the adventages and use of it, he asked me: " well, the insulation is stripped at every receptacle and device, so how would the megger readings be effective if so?"

Here's what i said:
"you megger between H-G,N-G,H-N(if you are sure there's no loads downstream), so since you are checking for any leakeage between the conductors insulation, at the receptacle or device the sonductor stripped ends on a terminal, which is away from the other conductor terminal your meggering."

I was just thinking about that now.
Does this answer sound good to you all?
Thanks.

I know lots of 25 year electricians that have not heard of a megger.

What you have described, a simple continuity tester would be a lot cheaper.

 

[augie47]

yes, but a continuity tester isn't going to indicate some of the wiring problems an AFCI now recognizes and for many industrial/commercial testing such as motor insulation, a megger can be a valuable tool, and for preventitive maintenance, a must.

 

[Buck Parrish]

And volts on a cable might make a difference in leakage.

 

[Charlie Bob]

I know lots of 25 year electricians that have not heard of a megger.

What you have described, a simple continuity tester would be a lot cheaper.

I belive a megger is a very useful tool for the residential electrician as well.
I had a guy called me once with a problem.His breaker kept tripping leaving him without power in the living room and another 2 rooms.
He'd already called a big electrical company, they sent an electrician.he spent there about 2 hours. He told the customer :"sorry, you have a problem but sometimes we just cannot find them"
Can you believe that?
He calls me, i go there, didn't have my megger that day, but everything tested OK with continuity tester.
The megger would have found it right away.
There's was a leak coming from the roof, leaking down inside the wall, getting that particular run of NM wet. The paper in the romex acted as a wick sucking up water into the romex. Insulation started to fail after a while, tripping the breaker after a certain amount of time.
Megger vs Continuity tester
=
megger 1-Continuity tester 0

 

[kwired]

I belive a megger is a very useful tool for the residential electrician as well.
I had a guy called me once with a problem.His breaker kept tripping leaving him without power in the living room and another 2 rooms.
He'd already called a big electrical company, they sent an electrician.he spent there about 2 hours. He told the customer :"sorry, you have a problem but sometimes we just cannot find them"
Can you believe that?
He calls me, i go there, didn't have my megger that day, but everything tested OK with continuity tester.
The megger would have found it right away.
There's was a leak coming from the roof, leaking down inside the wall, getting that particular run of NM wet. The paper in the romex acted as a wick sucking up water into the romex. Insulation started to fail after a while, tripping the breaker after a certain amount of time.
Megger vs Continuity tester
=
megger 1-Continuity tester 0

was this a GFCI or AFCI breaker, moisture in cable wil not normally cause standard breaker to trip as the fault current involved would be pretty low and the fault will probably eventually dry out the moisture. GFCI or AFCI will respond to many of these low currents if they are to ground and not line to line

 

[Charlie Bob]

was this a GFCI or AFCI breaker, moisture in cable wil not normally cause standard breaker to trip as the fault current involved would be pretty low and the fault will probably eventually dry out the moisture. GFCI or AFCI will respond to many of these low currents if they are to ground and not line to line

No it was a regular 20 amp SP breaker.

 

[K8MHZ]

If the person that has been an electrician for 25 years went through an apprenticeship school and never heard of a megohmmeter, he just wasn't paying attention. The megger has been around for over a century. (The name Megger became a trademark in 1903) It is far from a new fangled invention.

I say let him poo poo. It's his loss. Since he was so quick to discredit what you were trying to teach him, he has a closed mind, one that has been closed for a long, long time.

I own three megohmmeters. They are great if you know how to use them. If you don't, they aren't much more than expensive ohmmeters. At least one needs no batteries, just elbow grease.

Besides how they work, it is important to know what they test, how to conduct the test and record the results and what the results mean. Again, the are more than ohmmeters. They are used plot resistances over time that evaluate insulation breakdown and conductor capacitance.

 

[Charlie Bob]

If the person that has been an electrician for 25 years went through an apprenticeship school and never heard of a megohmmeter, he just wasn't paying attention. The megger has been around for over a century. (The name Megger became a trademark in 1903) It is far from a new fangled invention.

I say let him poo poo. It's his loss. Since he was so quick to discredit what you were trying to teach him, he has a closed mind, one that has been closed for a long, long time.

I own three megohmmeters. They are great if you know how to use them. If you don't, they aren't much more than expensive ohmmeters. At least one needs no batteries, just elbow grease.

Besides how they work, it is important to know what they test, how to conduct the test and record the results and what the results mean. Again, the are more than ohmmeters. They are used plot resistances over time that evaluate insulation breakdown and conductor capacitance.

Its funny, how some people feel intimidated, i guess, somtimes. When i was looking into buying my first megger, i asked this one elctrician i know, not the one i posted before, and he felt like i was checking out his knowleage i guess. he asked me " you want a what...?"
i told him a megger.
Then he replies: " never heard of such a thing, they coming up with new stuff all the time"

 

[Besoeker]

I was talking to this older electrician one time, he never heard of a megger before, he has about 25 years experience he said.

That's incredible. Shocking even.

 

[jumper]

That's incredible. Shocking even.

I love British humor.

 

[e57]

I belive a megger is a very useful tool for the residential electrician as well.
I had a guy called me once with a problem.His breaker kept tripping leaving him without power in the living room and another 2 rooms.
He'd already called a big electrical company, they sent an electrician.he spent there about 2 hours. He told the customer :"sorry, you have a problem but sometimes we just cannot find them"
Can you believe that?

Yes - I can beleive it... I'm a tenacious SOB and there have been things I can't find. Well sans the Time & Money to continue on the hunt. There are moments when locating a fault are better left to starting over as a cost analisis would dictate. That said, I have found things others have not - or were unwilling to find.

e.g. I was called out as a 3rd opinion on replacing a feeder in a very old industrial building with a lost neutral on 277/480Y. The client asked "are you sure the fault could not be located and just re-spliced?" A: I can charge you for the time, and do my best, and the customer wanted to limit that to a certain amount... 15 minutes with a TDR found that all 4 conductors were spliced at the same distances, and only the neutral was open at the same distance. I insisted they pull up some carpet squares under certianty I could find a box under the floor - and viola there was an access hatch cut into the sub-floor already... I had the right tool and the right know how... But if I tell many other "electricians" what a Time Domain Reflectometer is - I sound like this guy. That said there are different ranges of "electrician" ranging from "Rope-a-dope" to Wil'-E. Coyote.... Most of us are somewhere inbetween... (I am...)

He calls me, i go there, didn't have my megger that day, but everything tested OK with continuity tester.
The megger would have found it right away.
There's was a leak coming from the roof, leaking down inside the wall, getting that particular run of NM wet. The paper in the romex acted as a wick sucking up water into the romex. Insulation started to fail after a while, tripping the breaker after a certain amount of time.
Megger vs Continuity tester
=
megger 1-Continuity tester 0

Now I must ask - how a meggometer "found" it - rather than just 'identify' that there was an insulation condition issue, and the water was an issue without a break in the conductor insulation? Simply water on the paper would not cause the problem, water AND an opening in the insulation would. (Most NM uses conductor insulation nearly identical to MTW - 90 degree nylon jacketed PVC - which is damp/wet rated but the cable assembely with the paper and jacket is not - hence its rating.)

(That said I have seen first hand a simular issue that nearly resulted in fire due to wet paper in NM being wicked to a small cut in the insulation, and the water was carrying corroded AL oxides from an outdoor box....)

 

[e57]

I should also add - I have lost some major work to companies with a "Thumper" - but I have never had access to one - or even know how one works...

 

[K8MHZ]

I should also add - I have lost some major work to companies with a "Thumper" - but I have never had access to one - or even know how one works...

Are they available to the public? As far as I knew they were designed by ConEd and made just for them.

http://www.tecpower.com/tandd.htm

However, you are comparing apples to oranges. I know our apprenticeship program did not cover real-time fault metering. The "Thumper" has only been around for a dozen years or so and has a very limited use compared to a megger that has been around for a century, is used by thousands and is covered in (at least my) apprenticeship programs.

 

[Charlie Bob]

Now I must ask - how a meggometer "found" it - rather than just 'identify' that there was an insulation condition issue, and the water was an issue without a break in the conductor insulation? Simply water on the paper would not cause the problem, water AND an opening in the insulation would. (Most NM uses conductor insulation nearly identical to MTW - 90 degree nylon jacketed PVC - which is damp/wet rated but the cable assembely with the paper and jacket is not - hence its rating.)

(That said I have seen first hand a simular issue that nearly resulted in fire due to wet paper in NM being wicked to a small cut in the insulation, and the water was carrying corroded AL oxides from an outdoor box....)

Well 357, it didn't find it, per sei, but it did showed the insulation problem.So when compare to a regular continuity tester , the megger prooved to be the right tool for this application.

 

[zappy]

Yes - I can beleive it... I'm a tenacious SOB and there have been things I can't find. Well sans the Time & Money to continue on the hunt. There are moments when locating a fault are better left to starting over as a cost analisis would dictate. That said, I have found things others have not - or were unwilling to find.

e.g. I was called out as a 3rd opinion on replacing a feeder in a very old industrial building with a lost neutral on 277/480Y. The client asked "are you sure the fault could not be located and just re-spliced?" A: I can charge you for the time, and do my best, and the customer wanted to limit that to a certain amount... 15 minutes with a TDR found that all 4 conductors were spliced at the same distances, and only the neutral was open at the same distance. I insisted they pull up some carpet squares under certianty I could find a box under the floor - and viola there was an access hatch cut into the sub-floor already... I had the right tool and the right know how... But if I tell many other "electricians" what a Time Domain Reflectometer is - I sound like this guy. That said there are different ranges of "electrician" ranging from "Rope-a-dope" to Wil'-E. Coyote.... Most of us are somewhere inbetween... (I am...) Now I must ask - how a meggometer "found" it - rather than just 'identify' that there was an insulation condition issue, and the water was an issue without a break in the conductor insulation? Simply water on the paper would not cause the problem, water AND an opening in the insulation would. (Most NM uses conductor insulation nearly identical to MTW - 90 degree nylon jacketed PVC - which is damp/wet rated but the cable assembely with the paper and jacket is not - hence its rating.)

(That said I have seen first hand a simular issue that nearly resulted in fire due to wet paper in NM being wicked to a small cut in the insulation, and the water was carrying corroded AL oxides from an outdoor box....)

Is a TDR the same as a Megger?

 

[e57]

Are they available to the public? As far as I knew they were designed by ConEd and made just for them.

http://www.tecpower.com/tandd.htm

However, you are comparing apples to oranges. I know our apprenticeship program did not cover real-time fault metering. The "Thumper" has only been around for a dozen years or so and has a very limited use compared to a megger that has been around for a century, is used by thousands and is covered in (at least my) apprenticeship programs.

Is a TDR the same as a Megger?

Ah- no....

Answer kinda for both....

Megger (the company) makes both, as well as many other brands do too... And apparently now you can get all of it in one bulky really expensive package....

Zappy - I really am not the guy for describing a "thumper" - 'impulse generator' or its locating equipment. But a TDR is a signal generator that sends a low voltage - low energy signal out along two parralel conductors and measures reflected paterns at really high speeds and calulates distance to anolylies - some use a waveform that can be interpeted (which I prefer), and others simplify it to short or open and a numerical length. From what little I know about thumpers is that they are opposite in two ways - high voltage - high energy - often enough to jump gaps or even burn corrosion temperorily.... Where as a former member here (Marc the megger man) could go on - and on, and on about meggers and how they work and why... (I'm sure a number here have purchased one soley on his advise.... )

 

[Charlie Bob]

how much something like that would ?cost.