How the insulation tester works
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- Опубліковано 7 вер 2014
- This one is an explanation of how the insulation tester works in comparison to the meg ohmmeter. This video is part of the heating and cooling series of training videos made to accompany my websites: www.graycoolingman.com and www.grayfurnaceman.com to pass on what I have learned in many years of service and repair. If you have suggestions or comments they are welcome.
If you are a homeowner looking to repair your own appliance, understand that the voltages can be lethal, the fuels are highly flammable and high pressures are used. Know your limits. - Навчання та стиль
Im just buying my first insulation tester and this is the most informative video explanation ive seen so far on how to use on windings.
Glad it helped.
GFM
good video. and thanks for taking your time to explain the process.
Welcome
GFM
Thank you very much. Great explaination.
Welcome
GFM
you never showed a single test example !?
GFM, I read somewhere if you notice a downward trend or low megohms that it's possible you might have containments such a water in the system slowly generating acid and eating away your wire insulation. It was recommended to pump down the system and replace the filter dryer or if really bad readings replace the filter dryer twice.
I would like to know what your thoughts are on the subject and if it would be worth the trouble.
i need to know how to take an insulation test. i need to test a set of cables and don't know how.
Why aren't you using Kelvin Clips with the insulation tester on the left? I know they do not come with it, but that's what should be used for accurate testing.
Hey GFM, always enjoy your videos. Just wanted your opinion on those Supco M500 meggers, the ones that only have an LED scale, no number readings.
Would you say they're decent meters for checking the insulation on residential ACs?
Thanks!
juncho1977 Actually they are ok. I don't believe they will different voltages but will give a pretty good idea.
GFM
informative...
The meter on the right is if it is supposed to be stuck then it will confirm its stuck
The meter on the left is for if it is not supposed to be stuck, it will confirm if it is stuck!
Connections, Electrons, Resistance, Continuity, Open/Closed etc is what i mean!!!
Wire with hole in it = possibly stuck! How much? Crank up the voltage!
Would you use an Insulation Tester on a Condensing Unit conductors between a panel and disconnect? If so, can you demonstrate that?
You can, but mostly they are used on motor windings.
GFM
This kind used to test dc charging pile
Thanks a lot for sharing, I think that you have made the best explanation!
I hope that you please will answer my noob question. I want to test old insulation, glue, foam and so on, used in old amplifiers, if it is become conductive over the years. Is that the right tool for the job? (considering it's name) :-)
It will work if you know the voltage that normally is applied.
GFM
how does a 9v dry cell supply give 1000v in an electronic tester to test insulation?Is it just a simple voltage transformer inside the tester?
Beats me but it does. It is not a transformer because it is direct current.
GFM
grayfurnaceman Ah yes you are right and stupid of me to even suggest a transformer .Could it be a dc to dc converter then?
A transformer with the current switched on and off at some frequency on the primary side by a transistor. The secondary windings step the voltage up and then a voltage doubler/multiplier (which is just some capacitors and diodes connected in a special configuration) circuit steps it up even further while rectifying it to DC.
So, no, wasn't stupid of you to suggest a transformer.
If you're at all curious, you can look up "switch mode power supply" and "voltage doubler." The insulation tester has kind of a mix of both, I think.
Yup, probably uses a boost converter.
Why would anyone use a meter that utilizes only 9 volts to test a compressor that runs at 240 or 440 volts. The motor isn’t running at 9 volts so why would anyone use a standard ohmmeter to verify the condition of a compressor. A compressor that is full of liquid refrigerant will fail a megger test. It’s the reason for a lot of burnouts on units that are started up without the crankcase heaters being energized for 24hrs prior.. We teach and stress the use of megohmmeters in our apprenticeship program. In fact it is a part of annual service on large equipment to Meg the compressors and all motors. A Megger will detect insulation faults in a unit that are causing nuisance trips of fuses and breakers, where an ohm meter will not. Every pro HVAC tech should have one.
It doesnt measure "millionths of ohms"
It measures in megaohms which is x10^⁶ . Ohms. Millions of ohms..
I have an old megohm analog meter and I found this guys compressor to read less that 10 megohms and I though ok the compressor is shot, so I got out the digital supco megger and it read 20 which is as low as it can read and says to replace the compressor. Well I'm here to tell you thats been well over a year ago and its still running lol and drawing rated amperage go figure
I guess its not over till its over.
GFM
+grayfurnaceman Yeah I guess so, I told the guy to be saving up for a new unit though
I've been reading electrical blogs and the general concensus is that acceptable megger readings can be as low as 1 Megaohm per 1,000 volts plus 1 Megaohm for safety margin. Example, 480 volts = .5 Megaohm + 1 Megaohm = 1.5 Megaohm. This has proven to be true in my experience because I have yet to see a motor trip on 480 volts unless the megger reading was less than .5 Megaohm. Don't know if it holds true on scroll compressors but don't see why not
That Fluke multimeter is not a *_Megger._*
It does not measure insulation resistance.
The original *_Megger_* was an unusual hand-cranked device.
Please see here: ua-cam.com/video/1g97GV81BM4/v-deo.html
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There is a difference between a megger (megohm meter) and an insulation tester.
A megger uses a low voltage signal sent thru the circuit to test resistance. An insulation tester uses high voltage to attempt to break thru wire insulation.
GFM
@@grayfurnaceman A genuine Megger *_"IS"_* a high voltage insulation resistance tester.
What you are doing is mis-identifying ordinary multi-meters and resistance meters as a "meggers", simply because they all measure resistance up into the megohm range.
One of the first *_Meggers_* was a "hand dynamo", which allowed generation of voltages high enough to measure resistance in the megohm range and thus construction of a first portable insulation tester. The MEGaohm metER was then named as Megger and the word became a trademark name registered on 25 May 1903. The invention became a popular method of insulation testing and by the 1920s it was "well-known" by other engineers.
Please see: en.wikipedia.org/wiki/Megger_Group_Limited#Evershed_&_Vignoles
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@@Bodragon Good grief. why not just argue about how you pronounce "Tomato". I won't participate in this silly argument.
GFM
@@grayfurnaceman Fine but you started it.
And this is not about how we pronounce words differently - that's just anally retentive nerdy stupidity.
But it's really funny to see how you lash out when called out on a mistake and even double-down on it..
A Megger was actually a real, proper, dedicated high voltage insulation tester. The company even trademarked the Megger name.
That's a bit different from, say, tomayto, tomahto.
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@@grayfurnaceman I've just noticed that the Fluke 1587 is essentially a "Megger" since it is, primarily, an insulation resistance tester that measures at 1,000V.
That particular model looks remarkably similar to that Fluke 16, you've got there.
This leads me to suspect that you're not a bon- fide HVAC engineer, rather a "helper", otherwise you would not have made this mistake.
Please see here: www.testequipmentdepot.com/fluke/megohmmeters/1503.htm
I would love to see your comments.
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Thanks eh... Ü
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እንኳን ለታላቁ ላብይ ፆም አደረሳሽሁ ua-cam.com/video/DwtovSbadEA/v-deo.html