# Megger Tester for PM's?



## Sparky Mcgregor (Sep 7, 2015)

I noticed on another thread some of you guys use a Megger tester when trouble shooting motors. I'd like to get some experience using one but don't want to buy one myself as my budget is limited. My employer would probably purchase one if I could make the case that it would be a good PM test to locate deteriorating motor coils ect. Is this a reasonable use for a Megger tester?


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## macmikeman (Jan 23, 2007)

Supco 500. Very affordable.


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## John Valdes (May 17, 2007)

Sparky Mcgregor said:


> I noticed on another thread some of you guys use a Megger tester when trouble shooting motors. I'd like to get some experience using one but don't want to buy one myself as my budget is limited. My employer would probably purchase one if I could make the case that it would be a good PM test to locate deteriorating motor coils ect. Is this a reasonable use for a Megger tester?


Every electrician doing any kind of industrial work must have a megger.
Or know a motor shop that does work for free.


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## Essex (Feb 4, 2015)

In the UK all works are tested with a Megger prior to the installation being put into use. 500v are put down L-E, N-E and L-N. A new circuit would give an infinity resistance reading proving the circuit is safe to energise.


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## ponyboy (Nov 18, 2012)

Motor pms that incorporate a meg check are only as good as the documentation that goes with it. To truly see how a motor is trending all environmental factors must be recorded and taken into account at each check. My employers decided it's not worth it to do this since we've got an inventory on hand and any motor we run can be changed out in no time. They'd rather run them til they quit and then service them


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## MWayne (Nov 8, 2010)

If you are troubleshooting, then a megohm meter is essential. We always meg wires and cables after installing before putting 480V or more on them. Or if you have salvaged cable and want to see if it has any value other than as scrap. The first time you find the 25 HP motor is good and the problem was a sloppy connection in a junction box somewhere it will have paid for itself.

https://www.amazon.com/Precision-307A-Megohmmeter-Insulation-Low-Resistance/dp/B005FSX3A6

This is the one I use, based on Big John's recommendation. The analog is easier to understand if you are unfamiliar at first.


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## Flyingsod (Jul 11, 2013)

macmikeman said:


> Supco 500. Very affordable.


 That'd be ok for testing faults maybe but for PM its not gonna work so well.

The only way a megger is useful for PM is to take accurate readings at specific intervals and watch the trend. For that you will need a megger that gives specific values. Easa recommends recording humidity along with megger readings since high humidity will cause a drop. Your readings should be fairly flat when graphed. A single drop doesn't mean much. 3 or 4 successive drops might warrant cleaning and drying the winding. I agree with bisquits co though, except for high dollar motors OR motors that are critical its not worth the effort. 
Also theres no guarantee you will catch a failure before it happens. Motor windings don't always break down slowly. So you might convince your boss that you can catch a failure before it happens so you can schedule a motor change thereby preventing production down time... but if the next one that fails isn't caught you will have egg on your face.

Ive very rarely seen windings that are good with an ohmmeter that a megger will show as bad. It does happen but 9 times out of ten your multimeter will show the fault. My megger mostly gets used proving to myself that newly installed lines were not compromised in the installation.


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## just the cowboy (Sep 4, 2013)

*Do you install 480v wires*

For SAFETY reasons tell your boss, any time we pull new wire we should check it with a megger, so we don't close the switch into a faulted cable. A standard meter won't do this.

Also remember NEVER test anything that is hooked up to electronics, disconnect it first. It would not be good if you said "look boss this motor reads bad", and at the same time smoke the drive feeding it. oops.


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## Sparky Mcgregor (Sep 7, 2015)

It sounds like the general consensus is that a Megger wouldn't provide too much value in a pm scenario but may have some in a trouble shooting situation. I've never used one before so I'm having trouble picturing what information it would provide that a multimeter wouldn't. I'll youtube some stuff when I get home. That might clear it up for me. In the mean time does anyone think a megger is an essential piece of trouble shooting equipment in an industrial setting? Thanks for all the responses.


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## Flyingsod (Jul 11, 2013)

Yeah, its a pretty ubiquitous piece of test equipment for an industrial tech. 

For troubleshooting it only confirms what logic and a multimeter will tell you. For those of us that must know things for certain because of our personality (or job requirements) a megger is needed.

As far as what information it can provide... its actually a slim range. your Multimeter puts 9 volts on a system and reads resistance. A megger puts 500 or more volts on a system and reads resistance. That's the only difference. So what you can find with a megger is that uncommon situation where the insulation is good for 9 volts but not for 120/240/480 volts. 

Yes its essential for industry. Its value is overated in many cases. Its not even close to being as valuable as your Multimeter. Although if you have oil filled compressor motors MechanicalDVR taught me that megging is very useful and essential for PM.


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## Essex (Feb 4, 2015)

Flyingsod said:


> Yeah, its a pretty ubiquitous piece of test equipment for an industrial tech.
> 
> For troubleshooting it only confirms what logic and a multimeter will tell you. For those of us that must know things for certain because of our personality (or job requirements) a megger is needed.
> 
> ...




Over here every electrician owns a megger. Before any circuit is energised some dead tests are carried out in order to ensure as far as practicable that the circuit is safe. 

1. Megger the circuit at 500v to test to see if the insulation is in a good condition and there is no short circuits. 

2. r1 + r2 tests are done by measuring the resistance of the complete earth path of the circuit. r1 being the live conductor and r2 being the earth conductor. 

Only once these tests are complete and the results satisfactory should the circuit be energised and then live testing can take place.


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## ponyboy (Nov 18, 2012)

It's still a pretty valuable tool in my opinion. Yes it somewhat mirrors a standard resistance test from a dmm but I still prefer to megger heavy feeders and busway/swing plugs. Some heat trace cables require a megger reading as well. 


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## HackWork (Oct 2, 2009)

I like to megger apprentices.


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## ponyboy (Nov 18, 2012)

HackWork said:


> I like to finger apprentices.



You're sick



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## HackWork (Oct 2, 2009)

Biscuits said:


> You're sick
> 
> 
> 
> Sent from my iPhone using Tapatalk


Yeah, like you've never told your apprentice to hold the ends of these 500MCM feeders while you go to the other end to test them.


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## MechanicalDVR (Dec 29, 2007)

macmikeman said:


> Supco 500. Very affordable.


I think the Supco is great for a sales tool, but for diagnostics I use a real megohmmeter.


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## Big John (May 23, 2010)

What I like about megging is that it gives as close to real-world stress testing as you can get without putting power to the equipment.

I don't think most guys need a $3,000 Biddle, but when dealing with possible power faults, having a simple megger that will do 100, 250, 500, and 1000 volt steps can provide a heck of a peace of mind. 

Will a 9 volt continuity test often find ground faults? Sure. Will it tell you if 600V equipment is safe to energize? Not a chance.


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## Frank Mc (Nov 7, 2010)

Essex said:


> Over here every electrician owns a megger. Before any circuit is energised some dead tests are carried out in order to ensure as far as practicable that the circuit is safe.
> 
> 1. Megger the circuit at 500v to test to see if the insulation is in a good condition and there is no short circuits.
> 
> ...


This is whats suppose to happen here in Oz , i whine at the young guys telling them they all should have a meggar ,just like a pair of pliar,s..
The most common meggar used here is the Koyritsu...
https://www.google.com.au/url?sa=i&...9NHpuZDf7T_2gWcdwx5YLTsA&ust=1476432011247305

Frank


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## emtnut (Mar 1, 2015)

Sparky Mcgregor said:


> I noticed on another thread some of you guys use a Megger tester when trouble shooting motors. I'd like to get some experience using one but don't want to buy one myself as my budget is limited. My employer would probably purchase one if I could make the case that it would be a good PM test to locate deteriorating motor coils ect. Is this a reasonable use for a Megger tester?


I've NEVER worked in an Industrial plant that didn't have a megger !!

Large motors should never be commissioned without a meg test, and it's invaluable for troubleshooting !


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## Zog (Apr 15, 2009)

Every PM testing standard involves a megger test, motors, generators, transformers, cable, breakers, etc...I don't see how someone can not own one in this trade


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## Sparky Mcgregor (Sep 7, 2015)

Interesting, lots of different opinions on this one. I'll keep exploring. Thanks for all the feedback.


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## Electrorecycler (Apr 3, 2013)

For PMs, there is a product you can google called Megalert that regularly meggers the motor for signs of trouble. I only know about it because I had it pitched to me at a trade show a couple of years ago. It's designed for use on larger motors (100hp+). I can't tell you much more than that. Much like Biscuits said in an earlier post, my company would rather run the motors into the ground and swap them out for the spares then perform PMs on them, so the product didn't fly here.


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## Anathera (Feb 16, 2016)

I had a job a few weeks back that the engineer prints actually required megging before energization, the problem was the project was led lighting whipped off pvc pipe no way on earth I'm megging 20k in led lighting. They were all vapor tight too so it's not like I could just pop the disconnects.


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## Big John (May 23, 2010)

Anathera said:


> I had a job a few weeks back that the engineer prints actually required megging before energization, the problem was the project was led lighting whipped off pvc pipe no way on earth I'm megging 20k in led lighting. They were all vapor tight too so it's not like I could just pop the disconnects.


 Never heard of anyone megging branch circuits. If they forced you just keep it below the lowest nameplate voltage and you'd be safe.


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## Big John (May 23, 2010)

Electrorecycler said:


> For PMs, there is a product you can google called Megalert that regularly meggers the motor for signs of trouble....


 http://www.megalert.net/eng/product_family.php?family=MotorGuard&grupo=5

I think Lone Crapshooter was also describing this recently. That's pretty interesting looking. 

If it doesn't have temperature and humidity compensation it's useless for trending, but I suppose it could give a go/no-go "unsafe to energize" indication.

Definitely a product worth remembering.


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## brian john (Mar 11, 2007)

Anathera said:


> I had a job a few weeks back that the engineer prints actually required megging before energization, the problem was the project was led lighting whipped off pvc pipe no way on earth I'm megging 20k in led lighting. They were all vapor tight too so it's not like I could just pop the disconnects.


Proper test voltage for the equipment being fed.

We see specifications that require branch circuit meggaring, we always exclude it from our bids to electrical contractors and leave that up to them.


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## brian john (Mar 11, 2007)

Essex said:


> In the UK all works are tested with a Megger prior to the installation being put into use. 500v are put down L-E, N-E and L-N. A new circuit would give an *infinity* resistance reading proving the circuit is safe to energise.


Infinity=Full scale reading of the megger, not infinite resistance


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## Essex (Feb 4, 2015)

brian john said:


> Infinity=Full scale reading of the megger, not infinite resistance




Yes. In other words a figure the meter cannot achieve.


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## macmikeman (Jan 23, 2007)

Under a grand. http://www.mitchellinstrument.com/all-test-pro-motor-genie-motor-troubleshooting-tool.html

It's like the Supco deluxe!


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## triden (Jun 13, 2012)

macmikeman said:


> Under a grand. http://www.mitchellinstrument.com/all-test-pro-motor-genie-motor-troubleshooting-tool.html
> 
> It's like the Supco deluxe!


Fluke 1587 is also under a grand.

http://www.myflukestore.ca/product/...zsjnhhuF6DtseHUQsmSz_ZgfTw2aB7gpJIaAuJ58P8HAQ

Probably even cheaper in real currency (USD$$)


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## OSSElectric (Sep 28, 2015)

triden said:


> Fluke 1587 is also under a grand.
> 
> http://www.myflukestore.ca/product/...zsjnhhuF6DtseHUQsmSz_ZgfTw2aB7gpJIaAuJ58P8HAQ
> 
> Probably even cheaper in real currency (USD$$)


I found one brand new on ebay for $400


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## MechanicalDVR (Dec 29, 2007)

OSSElectric said:


> I found one brand new on ebay for $400


What brand?


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## MechanicalDVR (Dec 29, 2007)

*AMPROBE Battery Operated Megohmmeter*

I've had good luck with this meter. $172.50

https://www.grainger.com/product/AMPROBE-Battery-Operated-Megohmmeter-WP49529/_/N-b9p?s_pp=false&picUrl=//static.grainger.com/rp/s/is/image/Grainger/1WXH7_AS01?$smthumb$


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## triden (Jun 13, 2012)

MechanicalDVR said:


> What brand?


http://www.ebay.com/itm/FLUKE-1587-...715132?hash=item43f83f6d3c:g:dmUAAOSwXeJYFiTe

The new 'FC' models cost a little bit more because they have wireless connectivity and work with the Fluke phone app for logging and trending.


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## MechanicalDVR (Dec 29, 2007)

triden said:


> http://www.ebay.com/itm/FLUKE-1587-...715132?hash=item43f83f6d3c:g:dmUAAOSwXeJYFiTe
> 
> The new 'FC' models cost a little bit more because they have wireless connectivity and work with the Fluke phone app for logging and trending.


I had a 1587 basically since they were introduced, great meter. I've also had a few less expensive meters I've used for other than motor and compressor readings.


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