GS38 leads keep fusing....never used too though..

[NDG Elecs]

Hi Folks,

I have my first 'competent person' assessment in a couple of weeks and am starting to stress a bit!

Problem I have is my GS38 leads keep blowing. For a Megger1552.

They never used to do this. Have been using the same box of 500mA HRC fuses for ages, but cannot do any live tests with them now as they blow straight away and am down to the last few fuses in the pack!

I found the quote below from an old post on here but thought I would start a new post.
Trypod wrote:
"GS38 compliant probes use 500mA fuses and have an appreciable resistance making them unsuitable when loop testing on live systems.
The fused lead itself will add a small variability into the test result.
Test leads fused at 10A will provide protection from short circuit faults but will not fail under normal testing conditions"

I cannot change the fuses for 10A ones could I arguing that there is a 500mA in the tester itself? As I understand it the text of BS38, ahem, GS38 require 500mA leads.

Bit puzzled as they never used to blow like this, though TBH I dont use them much, as generally I use the standard issue leads.

Any help appreciated.

 

[ackbarthestar]

Hi Folks,

I have my first 'competent person' assessment in a couple of weeks and am starting to stress a bit!

Problem I have is my GS38 leads keep blowing. For a Megger1552.

They never used to do this. Have been using the same box of 500mA HRC fuses for ages, but cannot do any live tests with them now as they blow straight away and am down to the last few fuses in the pack!

I found the quote below from an old post on here but thought I would start a new post.
Trypod wrote:
"GS38 compliant probes use 500mA fuses and have an appreciable resistance making them unsuitable when loop testing on live systems.
The fused lead itself will add a small variability into the test result.
Test leads fused at 10A will provide protection from short circuit faults but will not fail under normal testing conditions"

I cannot change the fuses for 10A ones could I arguing that there is a 500mA in the tester itself? As I understand it the text of BS38, ahem, GS38 require 500mA leads.

Bit puzzled as they never used to blow like this, though TBH I dont use them much, as generally I use the standard issue leads.

Any help appreciated.

Leads in themselves do not blow fuses, only short circuits and overloads and from what you have said the likely cause is your test instrument. Connect a faulty instrument to a live circuit and goodnight in-line fuse.

The cause maybe that you are trying to take a live measurement on the wrong scale, that will blow the protective device.

 

[Richard Burns]

already answered

 

[ackbarthestar]

already answered

Must be using telepathic encryption........

 

[NDG Elecs]

Thanks for replies.


I get what you are saying. But why then when I am doing live tests with 'standard' leads it does not blow the built-in fuse if tester is faulty.

Do not seem to get any onerous results when testing with the non fused leads. Also can't really put the 1552 on the wrong scale with exception to the RCD tests.

The more I think about your answer the more I feel my wallet getting lighter!!

Thanks.

I hope it ain't the tester itself, only had it four years and it is well looked after.

 

[spark 68]

Hi mate,
I take it the fused GS38 leads did not come with the instrument ?

this is what is listed.
► Carry case with shoulder strap - holds MFT 1552 and documents
► Illuminated switch probe with white LED
► 3 wire test lead set: green, red and black
► 3 x Crocodile clips: green, red and black and red and black probes
► Mains test lead with BS1363 UK plug
► Instruction manual on CD
► Calibration Certificate
► 3 year manufacturers warranty
► Batteries

C/O testmeter uk.

As the instrument has an internal fuse and is designed for unfused leads then you don't require 500mA fused leads as well, you should only use the manufacturers specified leads which will be GS38 compliant in all other respects.
The instrument (and leads) have been designed to be compliant with all relevant standards.
As the EFLI hi-current test is taken @ 25A, then no wonder the 500mA fuse is blowing in the test leads.

 

[NDG Elecs]

Thanks spark68,

The leads did not come with the tester no. The GS leads are Megger ones.

I will look into the info you gave us. Will try and get an email off Megger confirming what you say. I have heard your argument before, but have heard some assessors not being happy unless the leads are GS ones. My assessor sounded very reasonable when I spoke with him so hopefully all will be ok.

Cheers mate.

 

[spark 68]

If you have GN3, look on page 81 (new book) read 4.1, where the instrument has built in protection and the manufacturer recommends non fused leads.
"it should be noted that such electrical protection does not extend to the probes and leads"
It does not say they should not be used, just noted.

 

[NDG Elecs]

Thanks again.

You are a diamond!

Just had a look in GN3. The paragraph is a little bit vague (as are many things from the IET!) so will try and get confirmation from Megger.

Ta.

 

[spark 68]

I think you are worrying too much,
The assessors are mostly ex-sparks too, and live in the real world, fused test leads are not much use if they keep blowing!

GS38 is IMO meant more for voltage indicators, multi-meters and the like, rather than MFT's which need to carry out hi current loop tests amongst other things.
If you think for a moment, Megger would not be allowed to sell dangerous test equipment.

The correct leads designed to be used for the instrument is more important, and will comply in all other respects, you need to be practical too.

 

[NDG Elecs]

Yeah, I probably am!

I can now at least argue my corner so to speak if he does raise the issue. And then pretend to be Fawlty Towers Manuel and not understand if he disagrees.......!

Muchos Gracious Senor!

 

[UKMeterman]

Hi,
Megger themselves do point out that 500mA fuses will go pop during certain live tests. 10A fuses would be better as in they won't pop during the live tests but do require a risk assessment...

 

[NDG Elecs]

Hi,

Never knew that, thanks.

I have had the GS leads around three yrs now but rarely use them as the provided leads are fine. I only got them as I thought I would need them for assessment purposes. I am sure I have done PFC and loop tests with them in the past but now both the fuses pop straight away.

If I can suffice without them then great....might get some 10A fuses just in case.

Cheers.