2.5mm t+e poor IR readings

[Theorysparky]

Just rewired a ring of about 50m,,,no difficult runs

tested it and N-CPC 280 meg

others around 800 meg

disconnect the ring and check each length between sockets and get

1000 meg +

connector block each socket outlet same readings on full ring

connected together its pants.

tested a reel of same cable 70m approx and the readings are around the

300 meg mark

test 80m of 1.5mm (same manufacturer )still on the reel and get 900+ meg readings

the cable is clipped only and has not been plastered yet

have i got a bad batch of 2.5mm ?

Cheers

 

[Oracle]

several years ago i had the same thing - but i found the issue after the walls had been bored!

At first i thought they had damaged the cable, but after ripping it out and checking it, we found no damage. It was a manufacturing defect basec cable too!

The other common issue is moisture/damp down the ends of the cables. Not so much of an issue with internal domestic jobs.

Or sometimes the outlets can give low ir results

O.

 

[Theorysparky]

my mate has the same cable and has similar readings,,,im thinking the cable is naff

 

[Lee321]

passes the test tho!

 

[Zeespark]

What make of cable are you using Theory, I generally stick to the likes of AEI - more expensive yes, but it hasnt ever failed Me yet.

AndyGuiness Drink

 

[Theorysparky]

Zee

its from Denmans,,, HANNI which have now gone bust !!!

NIC said that the readings are fine and that we shoudnt worry,furthermore to be fair to Denmans their branch manager phoned some of their more experienced contractors who also said they would be happy with those readings.

it then makes me think i am too much of a perfectionist with my results.....

i have a multitest Metrel which can give IR readings of >1000 which i have been used to on new cable....

am i right in saying with the fluke that it gives readings upto 200 ????

live and learn

 

[Zeespark]

As far as I know Fluke is 200Mohms just dont quote Me is all Pray

AndyGuiness Drink

 

[mikep]

Flukes are 500 Mohms

Mike.

 

[Robojin]

Megga's give >200Mohms so I guess you never know if the cable was 400Mohms or 900Mohms with one of them

I think AndyC uses a Megga

 

[Evans Electric]

Doesn't give us much chance if the cable already has a poor reading!!

 

[Andy™]

Megga's give >200Mohms so I guess you never know if the cable was 400Mohms or 900Mohms with one of themI think AndyC uses a Megga

i do. the 1552 is upto 299 on 500V. my older megger (insulation tester) goes to 999

 

[green-hornet]

Just to concur my Fluke gives readings above 500Mohms.

To be fair I would expect above 500 on new cable but above 200 is a normal reading given on most certificates.

 

[Andy™]

on a new cable, id expect over 999!

anyone know why the newer type MFTs have a max IR reading less than the older stuff?

 

[NozSpark]

If the cable checks out then it must be the accesories.....

I have a MFT 1502 and it goes up to 99Mohms @ 240v, >299Mohms @ 500v and >1000Mohms @ 1Kv

 

[cheggers]

my robin tester 200M

 

[SPECIAL LOCATION]

on a new cable, id expect over 999!anyone know why the newer type MFTs have a max IR reading less than the older stuff?

No need to go higher?

Because in reality 200Meg vs 999Meg would be such a negligibly small current flowing across the insulation as to have no effect on the electrical installation at all!!!

and is such a minuscule value as to be irrelevant...

considering you can have several 'mA' leaking to earth on various items of high leakage IT equipment

We are checking for LOW insulation resistance indicating latent defects when doing an IR test...

not seeing if our cable can reach the highest scale of our meter!

200Meg ohm is still 200x the minimum acceptable value in BS7671

 

[Andy™]

i know the readings are still acceptable and difference isnt worth much, just wondering more why the older test kits had a greater range than the newer ones

 

[Robojin]

on a new cable, id expect over 999!

Dependant on length presumably?

 

[Andy™]

Dependant on length presumably?

well yes, but i think a 500mtr drum of 2.5 is a little impractical for getting up the stairs in a house!