Megohmmeter Misconceptions to know
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- เผยแพร่เมื่อ 26 ก.ย. 2024
- Megohmmeters, clearing up many misconceptions.
1 Never use a Megohm (hipot) test in a vacuum
2 Scroll compressors can be perfectly good as low as . 5 megohms yet some meters show them bad at 20 megohms.
3 General megohm readings for open motors not sealed motors in a Refrigerant environments.
4 Contamination of moisture and acids is more likely a cause of low Megohm. readings. this can be solved by a cleanup process.
5 A megohmmeter with a selectable voltage range and digital readout should be used over a period of time to show trends and possible contamination. example Fluke 1503
6 Refrigerant, oils and quantities can affect the readings. also anything else connected to the circuit during testing.
7 See Emerson Copeland AE bulletin 1294 for more information.
How many good compressors have been condemned?
Ty, great to meet you at HVAC School 4th Symposium! You are THE FIRST person I have ever seen explain the use of a meghmmeter correctly!! I am a previous Carrier and Trane factory tech rep and I fought this misconceptions all the time. BRAVO!!
Thank you!
Great research TY. My goal as a junior technician is preparedness, in hopes of limiting uncertainty when i'm out there troubleshooting HVAC/R equipment. Your video has really helped me to understand a little more on my journey to becoming a more competent professional. Thank you
Great to see a different point of view. Again , Ty thinks outside the box !!!
Very Important video this Ty, I've seen many engineers using said handheld units and relying on what the stickers says on the front of the handheld meters ie it's bad below 20meg but not fully understanding what the reading means.
It's a great sales tool but unfortunately it's cost customers a lot of $
Mr. Ty, you are absolutely right. About a year ago I had the same experience. I was working on a 5-ton 3-phase commercial unit when it was requested by a technician to replace a bad compressor for a package unit. I was assigned the task of replacing the compressor when I got there the compressor was not turning on I used a megaohms meter to confirm and it was confirmed by the megaohms meter compressor was bad. I recovered the refrigerant and tested again at this time I noticed a megaohm meter indicating the compressor is good. I did not know the reason. I assume if compressor insulation is contaminated it will repeat itself once I charge the system with refrigerant. This is the first time someone tells me you are able to clean the system and be able to use the compressor again. Thank you very much for your help.
In Sweden 1Mohm is minimum.
A rule of thumb is 10Mohm/kV
Recomended 30sec to 1min test time.
For normal voltages, usually double the test voltage compared to working voltages.
EX:
100 till 240V (250 to 500 VDC test voltage).
440 till 550V (500 to 1000 VDC test voltage).
IEEE standard for electric motors recomends a value of (n+1) Mohm, where n is working voltage in kV.
ex: 115V = 0.115kV + 1 = 1.15Mohm.
Megger is great for testing al kinds of heaters.
Greetings from sweden
I love the detail!
I have yet to make it to Sweden 😢
Excellent video my man.Bravo
I've been trying to tell people this.. I own and use a Megohmmeter, but never use it to condemn a compressor. More so as an indicator of function. I've seen people sell/replace a less than 10 year old system, solely based on a red light from that little supco m500..
Keep up the good fight!
Good information.
Great points.
Nice video !
Thank you!
Great information Ty ! Thank you
Great video, thank you. The refrigerant and percentage of impurities modulating the reading is something I never knew. Do you have a video or information on using a Fluke 1507 MEGGER ( or any other MEGGER ) for example? What should I expect to see at what applied voltage in blower and condenser motors? Thank you again. .
Hello Ty wanted to thank you for your help with the Megger I ordered a Klein El600 tester
Ty. ET600
Awesome, let me know what you think of it.
Thanks Ty!
I love your videos! They’re so educational. I was wondering if you had any videos on boilers or if you could maybe do that for a future video. I work with a lot of boilers at my current job.
Thank you!
Boilers are one of my weaknesses but my friend Craig with AC service tech LLC has some great videos on boilers! Go check him out, he has a great channel and he's a great guy.
Steve Lav has a lot of good boiler videos.
Thank you Ty for your constant teaching.. there are always things to learn in our profession, no matter your experience level.
Question: Is there a test that you know of that can test the refrigerant oil/liquid in the system for contamination?
That way, you could take a test sample as another diagnostic tool.
Thank you I Appreciate that!
Yes there are several tests available.
"Qwiktest" makes a simple to use one.
NEW Calgone makes a phase 3 test kit that tests an oil sample.
Parker Sporlan makes an acid test kit.
You can also have an oil sample sent off for evaluation. We do this with chillers.
@love2hvac Thank you, Ty.... I will check check into those.
I have a Fluke 1587. 2.2 gigaohms. 50v to 1000v. PI and DAR tests
👍🏻👍🏻
Hey Mr.Ty
My all 3 prongs on compressor all show the same Omega reading and it is not short to ground .
And doesn’t comes on!?
Do i have to remove grounding cable and pipes before i use megger if i have elcb?
I have so many compressors kept triggering breakers or not running that all are BAD😂
Can you do a video with some actual compressors and digital style meter?
I will add it to the list
Ty would less than 20 megaohms on an open type motor be bad then or does the info on the video apply to all motors?
Generally speaking, open the motors above 10 meghoms are sususlly good. There is a lot more that goes into that. Even humidity can affect an open motor test.
Here is an article that relates
electrical-engineering-portal.com/how-to-measure-insulation-resistance-of-a-motor
@@love2hvac thanks for the info and link.
Ty you are a great help to the trade. Thanks
Hey this says the motor may be good, better turn the voltage up.
🙏🙏🙏👏👏👏👏💐💐
The more you know
Ty if you have time would you suggest a few meters that would work good. Maybe something $100 dollars and less. Thankyou
UEi DL379B or Klein CL800 is about $120
Those are the Cheapest quality meters I know right now
Some of the schools would order cheap ones for students to learn on. sometimes they worked great and sometimes not.
Jeff Bezoz place has has htis one with good reviews, even does capacitance and NCV but not temperature.
AstroAI Digital Clamp Meter Multimeter 4000 Counts Auto-ranging Amp Voltage Tester Measuring AC/DC Voltage & Current, Resistance, Capacitance, Frequency, Continuity, Live Wire Test, NCV Detection
Visit the AstroAI Store $37.99
@@love2hvac
Thanks Ty for the information. I think these are multimeter not mega ohm meter capable of doing the low reading you described in your video. If you have any further information on those I would appreciate. Thanks
If you have a standard HVAC digital multimeter that goes up to 60 or 100 megaohms, do you need one of those super fancy and super $$$$ expensive dedicated "Megger" machines? I'm talking about the really precision professional kind, not the midrange kind like that Supco.
Megger is not needed unless your in commercial or industrial checking pumps and big comoressors.
Sight glass with moisture or acid indicators are a better choice most of the time.
The last one you mentioned is not even a mid range, it's a low range that people use to sell new units.
@@love2hvac I wanted to be kind by not calling that thing a cheapie 😎. Why do you need the Megger at all? What special features does it offer, even for commercial?
@@realSamAndrew higher test voltage
A multimeter uses a low power output. A megger uses high voltage and low current.
The Meg ohm meter applies a high voltage to the windings and tells you if any amps escape through winding shorts. Unfortunately they can create pinholes in the insulation from people testing with too high of a voltage. Short story.. I have never had to diagnose a motor with one yet. The ohm scale on my regular fluke showed a short before I had to question much further. I think those meters are more for critical units and catching a developing issue. If not tested correctly they will create issues instead.
Did you reach out to the customer to offer a refund? jk
It's been on my mind for many years 😞
👍
Ty so much for the information , I learned a lot