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#40271 - 07/17/04 10:37 AM Why a Megger?
DougW Offline
Member

Registered: 06/08/03
Posts: 1083
Loc: North Chicago, IL
(Not the Brand Name "Megger", but...)

Re-equipping my truck, and the Wife asked if there was anything I needed that I didn't have before. Seeing my chance to buy some toys, (hehehe ) I suggested a few things off the top of my head, and then told her I needed to think about some others.

Perhaps I'm showing the limits of my experience here, but, since we pride ourselves in continually learning, I'll ask the question. What's a megohmmeter used for?

I know the primary use is to check insulation integrity, but how often do you use one? What are the other uses? Will the $249.00 one work as well as the $1899.00 one for "basic" use? Do I need one for resi work?

Just need to satisfy my brain on this.

Thanks in advance,

DougW

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#40272 - 07/17/04 11:16 AM Re: Why a Megger?
twh Offline
Member

Registered: 03/11/04
Posts: 898
Loc: Regina, Sask.
Maybe I'll show the limits of my experience, too. I have a cheap megger that I bought through ebay.

I've never used a megger on residential work. My main use is to confirm that a motor is good. Most ground faults in a motor can be read with an ohmmeter. Apparently they are a good tool for preventative maintenance, but I never get called until something has failed.

So, when the customer has a motor that they are going to install, or start, and I am asked to check it, I hit it with 500 or 1000 volts just to cover my ass.

tim

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#40273 - 07/17/04 11:59 AM Re: Why a Megger?
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...
An ohmmeter is effectively a low-voltage DC source, with measurement of current when the low-voltage source is applied to an electrical assembly—displaying resistance according to Ohm’s Law for the actual voltage and current.

Meg-o-meters are also resistance-measuring devices, but work at a much higher voltage, [250-5,000 VDC] to better stress insulation in an electrical assembly.

Meg-o-meter use often depends on policy of your employer or client. With experience, they can be indispensable for insulation testing.

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#40274 - 07/17/04 01:00 PM Re: Why a Megger?
pauluk Offline
Member

Registered: 08/11/01
Posts: 7693
Loc: Norfolk, England
I wouldn't be without one. They're very handy for finding leakage on motor windings, as already mentioned, or testing for suspected moisture incursion, and so on.

Under British "code," an insulation test is also specified for all newly installed wiring anyway, so a megger is considered an essential piece of equipment here. Our "Regs." specify a 500V DC test voltage for all 1-ph 240V and 3-ph 240/415V systems.

I have a couple of portable meggers, switchable ranges and with test voltages from 25V to 1000V.

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#40275 - 07/17/04 03:57 PM Re: Why a Megger?
DougW Offline
Member

Registered: 06/08/03
Posts: 1083
Loc: North Chicago, IL
Thanks to all who've replied so far.

The only time I've ever seen a need in my usual work was the unusual case of submitting a bid for a buddy who was looking at buying a house that had been involved in a fire. Our mutual friend (a County AHJ) suggested hooking a megger to any conductors not removed due to obvious fire area involvement to "prove" integrity for house inspection by the insurance company.

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#40276 - 07/17/04 04:20 PM Re: Why a Megger?
Roger Offline
Member

Registered: 05/18/02
Posts: 1779
Loc: N.C.
Doug, I agree with the others, but I'll add that unless you're doing alot of big commercial or industrial work that would require the calibrated results of a high dollar meter, I would go with an economy meter of a good name or quality.

Tell your wife that you need a megger and an Ideal Sure Test with the AFCI tester.

Tell her that these two meters must work together.

Roger

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#40277 - 07/17/04 06:24 PM Re: Why a Megger?
LK Offline

Member

Registered: 01/21/03
Posts: 1721
Loc: New Jersey
We use the megger on every pipe job, today we megged the wires for a pool instalation, last week we megged a take-over job, we use it more for residential work then commercial or industrial.
Buy that megger, and use it, checking your installation is the way it should be done, as years have passed the just get it done attitude is a standard practice.

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#40278 - 07/17/04 08:54 PM Re: Why a Megger?
Bjarney Offline
Moderator

Registered: 04/10/02
Posts: 2561
Loc: West-Southern Inner-Northeast ...

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#40279 - 07/17/04 09:33 PM Re: Why a Megger?
golf junkie Offline
Member

Registered: 04/22/01
Posts: 511
Loc: York, NE
Besides the uses allready listed I use mine often for troubleshooting direct buried wire ground faults.

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#40280 - 07/17/04 10:49 PM Re: Why a Megger?
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8540
Loc: SI,New Zealand
Damn,
Bjarney and Paul said it all!.
The Megger that I use has 250, 500 and 1000V ranges on it.
Like Paul said above, I would just stay at home if I didn't have a Megohm meter, a very useful and essential piece of kit, don't leave the house without it!.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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