problem with this incoming ?

[Andy™]

For a TT system yes, but this is not a TT system as there is no earth rod anywhere :_| There is a earth wire taht comes out of the wall at the front of the house in to a little box thats fixed in to the ground ( see pics ) there is 3 earth wires in the cu, 1 from the gas, 1 from the water and 1 from bonding in the downstairs shower :coat

even though there is no rod, doesnt automatically make it TN. maybe it should of had a rod. or maybe you just cant find it. or maybe water supply was used. lack of earth from service head/cable usually means its TT. see your diagrams in 7671.

and your picture clearly shows an earth rod, as godfather has already stated.

fast track course?

 

[Evans Electric]

Its looking now as the mighty Hornet says , earth connection not allowed by the network. Someone saw the need to make it TT . Could test the Ze on the cut-out earth terminal or make the enquiry ( See The Hornet)

Deke

 

[rob196]

Think I will need to make alot of investigations on this one, will contact the DNO and see what system they think it should be..........will have to find there number now and talk to them nicely ; \

 

[Andy™]

Think I will need to make alot of investigations on this one, will contact the DNO and see what system they think it should be..........

they will probably have TNCS on record if they have upgraded head to take TNCS. again, even if they say its TNCS, it doesnt mean that its TNCS thats installed

so, getting back to first post, what is the problem?

 

[green-hornet]

they will probably have TNCS on record if they have upgraded head to take TNCS. again, even if they say its TNCS, it doesnt mean that its TNCS thats installedso, getting back to first post, what is the problem?

I agree and as the Godfather has said in his post this is an earth rod.

The system you are looking at is a TT.

There may be a very good reason why it is a TT and should not be changed for a PME.

 

[Andy™]

There may be a very good reasom why it is a TT and should not be changed for a PME.

i can think of many....

 

[rob196]

they will probably have TNCS on record if they have upgraded head to take TNCS. again, even if they say its TNCS, it doesnt mean that its TNCS thats installedso, getting back to first post, what is the problem?

Problem was the service head says TN-C-S ( PME ) but with no earth cable, readings say TT but couldn't find a rod, ( I know there is a rod now ) if I treat is as a TT system and get the readings to match but they say it's a TN-C-S system, then they will not accept my readings. never been in this position before............

 

[rob196]

i can think of many....

please do.........

 

[Andy™]

then they will not accept my readings. never been in this position before............

who wont accept your readings and why wont they accept them?

 

[green-hornet]

Go andy I will let you answer, I am dying to jump in

 

[Andy™]

please do.........

have a search around the forum, plenty threads on this

but some main reasons:

under normal conditions, and more so fault conditions, there can be a voltage difference between 'earth' and true earth

if there is a broken neutral before the service head, all metallic services will rise to 230V.possibly higher depending where break is. and your RCD is guaranteed not to trip

ever wondered why you cant use TNCS on a caravan site? nice metallic caravan at a different voltage to the ground your standing on.

 

[Andy™]

Go andy I will let you answer, I am dying to jump in

you can join in if you want! maybe even let patch join in later with all the previous threads about this!

 

[green-hornet]

Problem was the service head says TN-C-S ( PME ) but with no earth cable, readings say TT but couldn't find a rod, ( I know there is a rod now ) if I treat is as a TT system and get the readings to match but they say it's a TN-C-S system, then they will not accept my readings. never been in this position before............

Never assume any earthing arrangement, even if you see an earth cable.

The label which denotes the earthing as a PME will have to be removed and should have been removed by the electrician who put it as a TT.

Your certificates should be filled out as a TT installation, the provider is not responsible for the earthing arrangements the consumer is.

 

[rob196]

Never assume any earthing arrangement, even if you see an earth cable.The label which denotes the earthing as a PME will have to be removed and should have been removed by the electrician who put it as a TT.

Your certificates should be filled out as a TT installation, the provider is not responsible for the earthing arrangements the consumer is.

I'm sure there is alot of threads on here but not having read them all i'm not as wise as you guys lol B-) you only learn went these things come up and i'm learning alot so would like to thank you all for your help and input. if you have any more advice to give me on this subject then it will be very much appreciated

 

[green-hornet]

I'm sure there is alot of threads on here but not having read them all i'm not as wise as you guys lol B-) you only learn went these things come up and i'm learning alot so would like to thank you all for your help and input. if you have any more advice to give me on this subject then it will be very much appreciated

Thats why we always try to help, I am glad you asked, its the idiots who never ask and do it wrong that really annoy me.

There are some very good reasons why pme is changed to TT, andy has stated some of them.

I personally prefer TT above all other arrangements, the earth if done correctly is far safer than PME, where earthing could be lost and no one would know.

Earthing by TT must be done correctly and tested properly, I do Ra as well as the Zs and Ze, if you do not have a tester to do Ra then a simple Ze will do.

The Ze would need to be below 200ohms anything above this could be unstable, some even say 100ohms.

Feel free to ask anything you are unsure of, this is the forum where we help not judge.

As my signature will attest.

 

[rob196]

Thats why we always try to help, I am glad you asked, its the idiots who never ask and do it wrong that really annoy me.There are some very good reasons why pme is changed to TT, andy has stated some of them.

I personally prefer TT above all other arrangements, the earth if done correctly is far safer than PME, where earthing could be lost and no one would know.

Earthing by TT must be done correctly and tested properly, I do Za as well as the Zs and Ze, if you do not have a tester to do Za then a simple Ze will do.

The Ze would need to be below 200ohms anything above this could be unstable, some even say 100ohms.

Feel free to ask anything you are unsure of, this is the forum where we help not judge.

As my signature will attest.

So in your oppinion I should treat this as a TT system and just do the test and hope I get the results I should from a TT system?

 

[Andy™]

So in your oppinion I should treat this as a TT system and just do the test and hope I get the results I should from a TT system?

just leave as TT. like i said, Ze can be upto 200 ohms, anything above should be considered unstable. Zs can be 1667 ohms when used with 30mA RCD/RCBO. i dont think you will have any problems getting acceptable readings. due to parallel paths, Zs of many TT systems are less than 10 (well, around here anyway)

 

[Andy™]

Thats why we always try to help, I am glad you asked, its the idiots who never ask and do it wrong that really annoy me.There are some very good reasons why pme is changed to TT, andy has stated some of them.

I personally prefer TT above all other arrangements, the earth if done correctly is far safer than PME, where earthing could be lost and no one would know.

Earthing by TT must be done correctly and tested properly, I do Za as well as the Zs and Ze, if you do not have a tester to do Za then a simple Ze will do.

The Ze would need to be below 200ohms anything above this could be unstable, some even say 100ohms.

Feel free to ask anything you are unsure of, this is the forum where we help not judge.

As my signature will attest.

Ra

 

[rob196]

just leave as TT. like i said, Ze can be upto 200 ohms, anything above should be considered unstable. Zs can be 1667 ohms when used with 30mA RCD/RCBO. i dont think you will have any problems getting acceptable readings. due to parallel paths, Zs of many TT systems are less than 10 (well, around here anyway)

So 4.56 ohms is fine then lol.........round here all the Earthing systems are questionable........Been doing another house this week and the service head says it's a TN-C-S but the earth runs straight up along side the armoured cable pass the service head and straight into the cu ( trouble is I cant see where the earthing cable comes from so not sure if there is a rod or not, Have only just gone self employed after studying for a long time and this is only the second job i've had to sort out ( just my luck :^O )

 

[green-hornet]

Ra

Ra RaROTFWL

Sorry thats what I meant I just keep pressing the wrong buttons on this keyboard

zzzzzzz:^O

Thanks for pointing it out, I type at about 30wpm but think only 10wpm

Guiness DrinkROTFWL