what supply system is this

[mblaquière]

Hello all, I understand this question may be pointless to ask as you guys can't see the whole installation and can't investigate further, but I wanted to know what kind of supply this is. I havent seen many supplies as im learning about all of it but I'm guessing its a tt system as there is no earthing conductor going to the met. Is that correct? The house is pretty old but is in a city centre so I thought a tt would be unlikely and there isn't anywhere I'd imagine to be suitable for an earth rod?
I've just realised that I can't upload a photo on my phone so ill describe it. There is a single cable feeding which looks like swa feeding the service head with the cables coming out the top going to the meter etc. there is no earth going to the MET. It has a 100a type 2 fuse in it. I hope that's enough of a description to warrant an answer? Wouldn't any of the other systems have an earth connected to the MET meaning it must be TT?
Thanks in advance if anyone can help

Ps I'm not doing work on the system I'm just learning about it and was intrigued to find out what the house had!

Thanks!

 

[telectrix]

sounds like it does not have an earth. all systems, both TN and TT should have an earthing conductor from MET to service head ( TNC-S ). incomer sheath (TN-S), or rod (TT).

 

[Darkwood]

If the earth comes out of the cutout to the MET then it is likely to be a TNCS
If the earth is connected to the sheath of the supply cable then it is likely to be a TNS
To a rod then TT

as mentioned above it seems the earth is missing are you sure that one of the earths in the MET or the consumer unit dosn't go out to a rod elsewhere??

 

[mblaquière]

I've not checked the cu but there is two earths coming out of the MET. One bonded to the gas pipe coming from the gas meter (right next to the elec service head) which I heard isn't recommended. And one going into the wall which I was guessing went to the cu but is it possible this goes to a rod then an earth goes to the cu? Wouldn't that be pretty dangerous let alone going against regs?

 

[telectrix]

without more info. it's not possible to comment further,

 

[Darkwood]

You say the gas bond to the met and out to the board so you think....you have been told that this set-up isnt recommended so who told you this and what are their qualifications.... as Tel says we lack too much info to carry on and i don't wish to speculate without so much as a pic at least.

You also say there isn't anywhere you imagine suitable for an earth rod.... well ive yet to find a property that i couldn't rod to the earth mass if it would require it..... unless its floating :bucktooth:

 

[mblaquière]

when we got our meter changed the engineer from edf that it shouldnt be that close? i shall try to upload a photo tomorrow or at least investigate further!

re the earth rod i presumed an earth rod would have to be inserted into soil to provide a low enough resistance and seeing as all the surrounding area is concreted i just presumed. would the rod be driven down below said concrete? also what are the regs concerning how far away a rod should be?

thanks for the info so far anyway!

 

[trev]

Given some of the ridiculous rod positions I've seen there certainly should be regs regarding this.

 

[Richard Burns]

This thread gives some pictures of service heads that may be useful to reference against but it sounds like you have no earth as already said.

 

[Guitarist]

You say that you're not working on the installation, just learning about it. Are you just curious, or considering a career in the trade?

 

[mblaquière]

I am training to be an electrician but haven't had a look at many service heads in real life just seen plenty of diagrams of tncs systems etc which in my opinion arent always useful! Why do you ask?

 

[brucelee]

you say there are 2 G/Y earth cables one goes to gas so this is extraneous conductive part and the green yellow cable is called a Main protective Bonding conductor
Try tracing the other check the water main stopcock if its there then its likely that you havnt got a earthing conductor which is the one that should go from your CCU to the MET if its a seperate external one near CCU and then onto either the sheathof the main supply cable and this should be visible to you for TN-S system using the sheath to return to the star point at the transformer totaly seperate from the neutralin consumers and suppliers side, or into the cutout (WHICH YOU SHOULD BE ABLE TO SEE EASILY were it will be linked with neutral giving you a TN-C-S system which is combined using a PEN conductor and mutiple earthing system with multiple rods along the route back to star point at transformer or alternativly from MET to a earth rod and then the general mass of earth back to suppliers earth rod then to star point of transformer

If you have no earthing conductor then temp fit a earth rod get onto DNO and ask about possibility of having a TN-C-S system

only way to check if there is an earth present is to carry out I&T but dio you have necessarry calibrated test equipment and are you competent to do this using an earth fault loop impedence tester if no earth then the Main protective bonding is acting as your earth to the gas or water


try posting some pictures as this will help people replying and give them some idea

 

[Guitarist]

I am training to be an electrician but haven't had a look at many service heads in real life just seen plenty of diagrams of tncs systems etc which in my opinion arent always useful! Why do you ask?

It helps to know who we are talking to when it comes to terminology.
I'm sure you can appreciate that we also get a lot of builders/plumbers/handymen pretending to be "just interested" in order to get advice on how to carry out electrical work which they charge for.

 

[mblaquière]

Thanks for the replies guys, havent had a chance to scout out the main stop cock or trace the g+y's from the CU yet but i can see two coming out of the CU both look about 10mm in size. Below is a picture of the service head i realize it doesnt show a lot of the install but thought it may help! thanks again and i didnt mean to come across arsey in my last post!

thanks!

 

[SPARTYKUS]

Whats the fat G&Y at top of piccy?

can you tell is the MET part service head or separate.

 

[Guitarist]

Looks like part of the head to me, especially as it's on the neutral side, so TNC-S.
Love how you managed to capture the spider as well

 

[mblaquière]

Haha I had to get the little guy in there too! The g+y at the top is just one of the ones terminated in the MET. Ah ok I didn't think about that! I didn't expect the MET to be able to be attached to the head but that makes sense! Thanks guys! That would make the supply cable to be swa but it looks very thin for swa? What is the minimum size you can get? Thanks for clarity again guys much appreciated!

 

[trev]

Could be a split concentric

 

[Guitarist]

What trev said

 

[Engineer54]

Could be a split concentric

It is, (or a straight concentric) far too small to be a PILC cable!!