Ze to high ??

[Lyngarth]

Hi

Was checking my house today, as will be replacing the cu very soon. When doing the Ze I get 0.37 on a TN-C-S now its only a little high but is it to high to leave??

Asked the chap I'm working with, and was told to check it in the morning and at night, ( would that make any difference??) and have used his tester as well but still get 0.37.

Should I get it sorted or will it be OK

Cheers

Lyngarth

 

[Andy™]

contact DNO and tell them Ze is too high. but in reality, for that reading, its doubtful they will do anything about it. unless your right next to the substation, in which case it should be much lower

 

[paul b b]

it will vary throughout the day, also if you are a right the other end of the suppliers line you will get a higher reading.

im sure some one will come back with a more tecnical reply

 

[Andy™]

voltage may vary througout the day. but the impedance should always stay the same

 

[paul b b]

ahhhh sorry for wrong info given.

 

[green-hornet]

I did a rewire 2 years ago with the same kind of readings it was actually 0.38.

I informed the DNO and they said not to worry too much, I put the reading down on my certificate and I made notes that the DNO had been contacted and was aware of my findings.

Incidentally my assessor saw the certificate and told me I had done everything in my power to comply with all regulations,besides all the disconnection times where acceptable.

 

[Lyngarth]

Hi

Thanks for the replys, I'm the last house on my road and the local sub station is the other end, so quite a way from it.

Will get them a call just to see but when I fit a new Cu will it be ok to put that down on the cert as max Ze ?? being it higher than the books tell me.

Cheers

Lyngarth

 

[Andy™]

just note what it is and what you have done about it - thats all you can do

 

[Lyngarth]

OK will do just thought I would check first.

Many thanks

Lyngarth

 

[PC Electrics]

Are you sure it's TN-C-S?

This picture shows a TN-S head, but it looks just like a TN-C-S and my assessor tells me it's a common mistake to confuse the two.

http://www.photobox.co.uk/album/28385663

To be honest I think I'd just leave it. It's not at a level where it is likely to cause any problems with disconnection times in a typical domestic (and anyway you'll be testing for that when you change CU). As a sanity check, you could ask your immediate neihgbour if they'd let you check their Ze and if you get much the same result you can be reasonably sure it's down to the distance from the transformer.

 

[Andy™]

easiest way to check that service head would be loop L-N and L-E. if its the same, most likely TNCS. if different, most lokely TNS

 

[Lyngarth]

Hi

It is a TNCS. I have just been round to next door and tested there Ze, and got a reading of 0.36 so just under my reading.

So will just let it be for now, but when I phone to get someone out to remove the seal on the main fuse (unless it falls off in the wind over the next few weeks) I will check and see what they say.

Cheers all

Lyngarth

 

[SteveH37]

HiIt is a TNCS. I have just been round to next door and tested there Ze, and got a reading of 0.36 so just under my reading.

So will just let it be for now, but when I phone to get someone out to remove the seal on the main fuse (unless it falls off in the wind over the next few weeks) I will check and see what they say.

Cheers all

Lyngarth

You really do have to watch those seals nowadays, even the slightest breeze can make them fall straight off!