TT Earth system tester

[Prytaneion]

I have to install a TT Earth Rod on a rural new installation. Can some kind sparky please point me in the direct of a hire company that will hire out a tester? My old megger 1502 won't do this and as there is no power on site at the moment, I need a battery powered tester for Ze.

 

[Nigel]

If you mean Ra then this mob does them:

Megger DET4TD2 - Express Instrument Hire - http://expresshire.net/product/electrical-test/earth-tester/megger-det4td2/

 

[rolyberkin]

Is there not another local sparky who will tip out to do it for you for a few beer tokens? I can be bought for a couple of decent bottles of red but not as far away as Bognor!

 

[Fitzy]

The kewtech KT65 does earth rod testing, check if any of your mates have one of these MFT.

 

[Prytaneion]

I'll ask around but since forced retirement through ill health, I've lost touch with a lot of my mates in any case. the KT65 is a bit up market for them!!

 

[Prytaneion]

Hi Roly - The job is a rural site near Bath so travel is a problem from here. I might just bite the bullet and hit ebay...

 

[Flanders]

Just to confirm you will nead an Ra tester not a ze tester as there is no Ze on a TT system ☺

 

[Prytaneion]

Hi Flanders (Whoo-Hoo) - Ra it is - my mistake... :0)

 

[Nigel]

Just to confirm you will nead an Ra tester not a ze tester as there is no Ze on a TT system ☺

Yes there is.

 

[rolyberkin]

I had a similar job and bought a megger det3tc from ebay a while back and used it once! However I have got another job coming up in 2019 where I will use it again!

 

[Prytaneion]

Hi Roly, yes mate, I have a similar problem but today I have found a local sparks who will test the earth rod (s) actually there are two 2M rods - for fifty quid so I'll probably go with this option. TT systems are a pain in the butt, however, because they are what they are, it's imperative to get it right. Thanks for the chat though...

 

[Flanders]

Yes there is.

I have always thought Ze was the external earth loop resistance back to the transformer if there is no supply earth how do you get a Ze reading , or am I missing something ?

 

[Prytaneion]

The loop back to the star point on the transformer is through an earthing rod or rods. About 2 metres worth of copper beaten into the ground or tape etc.

 

[Prytaneion]

See the readings here: MAXIMUM Ze at origins of TT, TN-S & TNC-S, - https://www.electriciansforums.co.uk/threads/maximum-ze-at-origins-of-tt-tn-s-tnc-s.36256/

 

[Flanders]

The loop back to the star point on the transformer is through an earthing rod or rods. About 2 metres worth of copper beaten into the ground or tape etc.
View attachment 45777

View attachment 45776

Thanks very much now it make sense .

 

[Prytaneion]

 

[Nigel]

I have always thought Ze was the external earth loop resistance back to the transformer if there is no supply earth how do you get a Ze reading , or am I missing something ?

You said there was no Ze on a TT. There is on a live system and this would normally be the way of measuring the earth. However on a new installation with no supply you then need to measure the Ra which ia a dead test.

 

[Flanders]

You said there was no Ze on a TT. There is on a live system and this would normally be the way of measuring the earth. However on a new installation with no supply you then need to measure the Ra which ia a dead test.

Yes thanks essex ( You don't need to tell me twice ☺ )I dont no why but I thought RA was used for the live test aswell , Thats why you earth an earth loop tester to test it , now i do feel stupid. I realise now the earth path back to the centre point is the a actual Earth (thanks to the pic the OP posted) By the way just checked in the BBB and its RA not Ra, dont want the symbol police saying we are using the wrong one ☺

 

[Nigel]

Yes thanks essex ( You don't need to tell me twice ☺ )I dont no why but I thought RA was used for the live test aswell , Thats why you earth an earth loop tester to test it , now i do feel stupid. I realise now the earth path back to the centre point is the a actual Earth (thanks to the pic the OP posted) By the way just checked in the BBB and its RA not Ra, dont want the symbol police saying we are using the wrong one ☺

You are not stupid. The term ‘Ra’ is used a lot on here incorrectly.

 

[Prytaneion]

We all make mistakes,,, that's why they put rubbers on the end of pencils...
Don't be too hard on yourselves guys. The fact that you hang around fora like this shows you have the best of intentions and the welfare of your trade at heart. Thanks for your help and advice.