High PFC discovered prior to NIC inspection on monday!!

[Martynrosscampbell]

Nothing like leaving it to the last minute ay?

So NICEIC domestic installer inspection on Monday morning. 1st job to show is the work I've done at my own property! of course that means that until now I've not done anymore than the basics. r1 +r2 on the circuits I've touched and an RCD test when I powered up. no schedule of results, no Ze test, no PFC etc. thought id better get it sorted this afternoon!!Bad form I know but its my own property and theres always something better to do!!!

Ze came in at 0.02!
PFC at 19.9 KA this is as high as my 1552 will measure.

supply transformer is less than 100 yards away which explains the reading.
Ive read so far that its fine to leave the 6KA breakers in because I can use the 33KA of the 1361 main fuse.

Anybody know if this is definitely NOT OK? if There is someone out there who really thinks I need to do something about it then let me know and also if you think the inspector will be alright with it.

Anybody know what these inspectors are like? Im beginning to worry now!!!

Thanks

 

[Spark123]

Reading page 54 of Guidance note 3 it says a consumer unit can be rated up to 16kA where certain conditions are met, firstly try new batteries in your tester!

 

[EFLImpudence]

Use your wander lead and see what the measurement is.

Meters are not accurate at low values.

 

[Spark123]

Wander lead??

 

[EFLImpudence]

Yes, a known resistance.

 

[Spark123]

Why? A wander lead is used for measuring R2 of circuits or MPBs, not sure how you intend it to be used, you can't really take it out to the substation.

 

[flyingsparks]

Are you sure your leads we're zeroed properly?

 

[EFLImpudence]

Why? A wander lead is used for measuring R2 of circuits or MPBs,

Yes, but it is a length of wire which has resistance.
You could use it for tying your shoes.

not sure how you intend it to be used,

You put it in the loop and deduct the known resistance from the result.
A loop reading of 0.02Ω is not accurate.

you can't really take it out to the substation.

Why would you want to?

 

[Martynrosscampbell]

Im also not sure what your expecting me to do with a long lead? am I just being a bit slow!

leads were nulled and checked and twice. it did read a 0.01 on one of the Ze tests!!

The development is less than 10 years old and the supply transformer was installed at the time so im guessing its been like this since it was built!

let me know what to do with the wander lead and i'll give it a go!
Thanks

 

[Martynrosscampbell]

sorry too slow. i'll try it!

 

[Spark123]

I don't think you can null the leads on a MFT1552 for anything other than a continuity test.

 

[Lectrician]

I would un-null the leads, test again, and then detect the reading you get on continuity when shorting the un-hulled leads. See if this agrees with your 0.02.

If you're sat on top of a stonking TX, this reading would be expected. The DNO fuse will provide "back up protection", by limiting "let through energy". Both good phrases to please mr NIC.

 

[Martynrosscampbell]

so, wander lead resistance = 0.69
Ze test with wander lead = 0.69
Ze with standard lead = 0.01

So back up protection from the cut out fuse it is then!

The supply transformer takes up a space which could have been a parking space or a single garage! that includes space around it. Its probably more like 100 feet away from my cut out. transformer is probably wrong terminology I know!

so any other advice for NIC inspection? question I should be prepared for etc?

thanks

 

[flameport]

so, wander lead resistance = 0.69
Ze test with wander lead = 0.69
Ze with standard lead = 0.01

Even with a transformer 100ft away, it can't be 0.01
If the cabing from the transformer to your property is a pair of 25mm² copper conductors, a 30m length of those is 0.04 ohms on their own.
Actual cables may well be smaller.

In the real world, any Ze reading under 0.1 is grossly inaccurate and of no value to anyone.
Fault current being too high is never an issue with domestic supplies, and for those larger installations where it could be, it would be derived by other methods.

so any other advice for NIC inspection? question I should be prepared for etc?

Forget about the 0.01 result - it is wrong.

Other things:
All of the standard tests, what order to do them in, what results would be expected and why.
Safe isolation procedures
The other sections of the Building Regulations - energy efficiency, fire prevention, structure, etc.

 

[EFLImpudence]

Ze came in at 0.02!
PFC at 19.9 KA this is as high as my 1552 will measure.

Apart from anything else, you could check your or the meter's maths.