My new Megger MFT 1730

[JohnW2]

Well good luck with that. As I say I don't doubt your competency...

Thanks - but the chances of my competence ever being challenged are extremely small (how often have you heard of it happening?) and, as I just wrote, I am fairly confident that I could demonstrate my competence if I ever had to!

... but then that said this thread as is normal in this section has gone way off topic.

Indeed - but nothing new and, if I dare say so, I think it was you who started it by essentially asking why a DIYer would want an MFT! As I have subsequently explained, there is a short answer to that - i.e. that anyone who undertakes any electrical work (no matter how infrequently or how 'simple') could well be accused of committing a criminal offence if they do not undertake 'proper testing', which requires (amongst other things) the appropriate test equipment to be bought or hired.

Kind Regards, John

 

[EddieM]

Anyhow, reading this forum over the years has educated me a great deal in how little I know about the subject. You may feel that odd but actually it is beneficial to know you don't know that much about something rather than blindly plough on.

 

[EddieM]

Thanks - but the chances of my competence ever being challenged are extremely small (how often have you heard of it happening?) and, as I just wrote, I am fairly confident that I could demonstrate my competence if I ever had to!
Indeed - but nothing new and, if I dare say so, I think it was you who started it by essentially asking why a DIYer would want an MFT! As I have subsequently explained, there is a short answer to that - i.e. that anyone who undertakes any electrical work (no matter how infrequently or how 'simple') could well be accused of committing a criminal offence if they do not undertake 'proper testing', which requires (amongst other things) the appropriate test equipment to be bought or hired.

Kind Regards, John

Yes, I guess it was me that threw it off course.

 

[eveares]

I have an RCCB extension lead.
That is an RCCB and socket on a piece of wood connected to a plug which I use to verify that the meter still gives the same results.

OK, but when your meter says your RCCB took X Milli seconds to trip at let say 1X rated trip current, how do you distinguish between a inaccurate reading on your MFT and natural tolerances in your RCCB?

Another Example: You test a 30mA RCD on a ramp test and your MFT reports it tripped at 22mA, but it actually tripped at 35mA, how do you detect such a faulty MFT with just a standard RCD/RCCB!?

 

[EFLImpudence]

OK, but when your meter says your RCCB took X Milli seconds to trip at let say 1X rated trip current, how do you distinguish between a inaccurate reading on your MFT and natural tolerances in your RCCB?

The point is that your meter has just been calibrated so

Whatever readings you get now may be considered accurate. Do them several times and see if there is any variation.
If you test in a month, a year, and the readings are the same, then you can be fairly certain the meter is still accurate and nothing has changed.
If they are different you can investigate and determine why - meter or RCD.

Another Example:

You test a 30mA RCD on a ramp test and your MFT reports it tripped at 22mA, but it actually tripped at 35mA, how do you detect such a faulty MFT with just a standard RCD/RCCB!?

Not quite with you here.
How do you know it actually tripped at 35mA?
If it reads 22mA today and the same in a month/year you can be certain that's what it is.

 

[SimonH2]

I do electrical work (Very simple) once in a blue moon. That is because there is no need to?

For some of us, it's different.
For me, I tend to be doing electrical work as I "do up" each room - additional sockets, changes/additions to the lighting, and so on. By possessing an MFT (which I was lucky enough to pick up exceedingly cheaply a few years ago) I am able to do proper testing each time.

 

[scousespark]

I thought this was a PUBLIC forum, so don't see any reason Eddie should have to justify participating in any threads. It's irrelevant if a member is a diyer or a pro and is a novice or has years of experience.

 

[eveares]

EFLI, I was referring to your statement that you can avoid ever having to get a MFT calibrated at a proper calibration facility with test standards by simply testing it with a home made RCCB/RCD rig?

I think I may have misunderstood you.

 

[JohnW2]

I thought this was a PUBLIC forum, so don't see any reason Eddie should have to justify participating in any threads. It's irrelevant if a member is a diyer or a pro and is a novice or has years of experience.

Good to see you, but ...

... c'mon, you really are living up to your reputation - why always me?! I did not ask Eddie to "justify" his participation in this forum, or in this thread - I merely said that I '"wondered" why he participated in a DIY Electrics' forum, given that he had said that he only did "very simple" electrical work and even that only 'once in a blue moon'. Was that not reasonable 'wondering'?

Kind Regards, John

 

[JohnW2]

EFLI, I was referring to your statement that you can avoid ever having to get a MFT calibrated at a proper calibration facility with test standards by simply testing it with a home made RCCB/RCD rig? I think I may have misunderstood you.

I think you did misunderstand. I think EFLI was describing what I also do - get the machine calibrated, then immediately make a note of the results one gets (for things like RCD testing) with one's 'check box'. On subsequent occasions one compares the new check box results with the original (immediately post-calibration) figures to see if they have changed significantly.

Like EFLI described, one of the things my 'box' contains is an RCD. When I do re-checks with the box I am looking for any changes in the readings my MFT gives (with the same RCD) as compared with its readings immediately after calibration. One might fear that the 'test RCD' might change over time, but the technique is essentially 'fail safe'. If one gets the same readings with one's MFT as one did immediately after calibration, it is all but inconceivable that a change in the RCD will have exactly mirrored a change in the MFT, so as to give the same readings even though the MFT had gone out of calibration. If the readings do show a change, then one investigates further (the first thing being to compare one's MFT's results with those obtained with someone else's MFT).

Kind Regards, John

 

[scousespark]

I was following this thread and thought Eddie asked a good question. I was thinking a 1730 is high spec for occasional use. That's not having a go at everares as he has got a great deal.
I just thought it odd to question why Eddie joins in just because he does little ekectrical work.

 

[Adam_151]

EFLI, I was referring to your statement that you can avoid ever having to get a MFT calibrated at a proper calibration facility with test standards by simply testing it with a home made RCCB/RCD rig?

I think I may have misunderstood you.

I can't see how a checkbox can save you anything in time/convienience for someone who just has one set of gear, it can add a little bit of piece of mind though. If you are not sending the tester off for cabration and are instead testing it against a checkbox then you need to be getting the checkbox calibrated once a year instead (don't think you could get a home made one calibrated!).... not really gaining much with 1 test set, but if you were a company with 10 it can be worthwhile Plus with 1, if your readings change? what do you send off for repair? the tester or the checkbox?

 

[EFLImpudence]

That's overcomplicating it somewhat.

The checkbox is not going to fail on everything at once.
If all but one reading is the same as last time then it would be apparent what had gone wrong.

The point is you are looking for the same results as last time. If they are then all is well. If not investigate.


It would be the same if you had two machines. If the results match now and again in the future then you can be certain they are both correct.
If not then one has gone wrong.

 

[JohnW2]

I can't see how a checkbox can save you anything in time/convienience for someone who just has one set of gear, it can add a little bit of piece of mind though. If you are not sending the tester off for cabration and are instead testing it against a checkbox then you need to be getting the checkbox calibrated once a year instead ...

As EFLI and myself have explained, with a check box one is merely ascertaining whether the results one gets with one's test equipment remain the same as they were immediately after the equipment was last calibrated. As I said, the chances of the readings remaining the same despite the equipment going out of calibration (because the check box had changed by exactly the same extent) are incredibly small.

Kind Regards, John

 

[JohnW2]

I was following this thread and thought Eddie asked a good question. I was thinking a 1730 is high spec for occasional use. That's not having a go at everares as he has got a great deal.

Yes, it was a perfectly reasonable question (which I think was more about why a DIYer should require any sort of MFT, not just the level of its spec) and, knowing your views, I am a little surprised that you were not supportive of my response ...

... because I pointed out that, even if a DIYer undertakes electrical work only very occasionally, it is still necessary that the work (and, where appropriate, relevant parts of the installation) be 'properly tested' - and that requires the DIYer to either buy or hire appropriate test equipment, and to become competent in terms of its use and interpretation of the results. We all know that most DIYer's don't do that, but they really should.

Kind Regards, John