TT or Tncs

[oneofthedamned]

Lads, just a quick one I have attached a picture (I hope) of the BS cut out of a house I have been asked to move a cooker switch in. The CU is a 16th edition split load job and only been in about 3 years fitted by the previous owners brother when he rewired the house. It looks very neat and you would assume to look at it that he knew what he was doing, but the main earth is to a rod and there is no rcd protection for half of the board. Also the main fuse has been pulled presumably to fit the new instalation so why not fit the earth lead when the fuse was out and have a Tncs system?

I have taken no measurements so I don't know how good the earth is but I can't think why somebody would TT when PME is available and if they did TT why no RCD.

Should I just connect the earth and check the bonding or fit an RCD for the unprotected half. I have expressed my concerns to the customer and said I will get back to him. Any suggestions? :|

 

[green-hornet]

First of all you should never convert a TT to a TNC-S.

It is also illegal to do so!

If it is a TT then rcd protection would be required for all circuits.

I would contact the DNO and see if they could verify the earthing arrangements and you would need to contact them to inform them that the seal has been broken.

 

[Andy™]

Also the main fuse has been pulled presumably to fit the new instalation so why not fit the earth lead when the fuse was out and have a Tncs system?I have taken no measurements so I don't know how good the earth is but I can't think why somebody would TT when PME is available and if they did TT why no RCD.

Should I just connect the earth and check the bonding or fit an RCD for the unprotected half. I have expressed my concerns to the customer and said I will get back to him. Any suggestions? :|

you cannot DIY PME. only DNO can, and thats if their network is upto it.

there are many reasons to ditch PME in favour of TT

 

[0151]

looking at that cable and the new henley cut out. if the DNO have not put a TNS split con cable in and just a concentric hybrid then leave it as TT

 

[batty]

That is a pme cut out but there may not be pme in the area if the phase to neutral loop is over .35ohm dno will not give pme earth or they should not. I do worry about what goes on and the work done by unexperienced sparks. I have a football club that I am testing at the moment. It has a 3 phase supply but is TT. from the cut out the tails go into a mem 3 phase 100 amp metalclad switchfuse and from there the tails go approx 10 meters to a 60 amp 3 phase switch fuse. When I tested the earth fault loop it was 180ohm. It would be quite frightning as to what could happen if there was a phase to earth fault on any of this switchgear. I installed a new rod and got loop down to 30ohms. I have got to install a Rcd before these switchfuse.

 

[green-hornet]

That is a pme cut out but there may not be pme in the area if the phase to neutral loop is over .35ohm dno will not give pme earth or they should not. I do worry about what goes on and the work done by unexperienced sparks. I have a football club that I am testing at the moment. It has a 3 phase supply but is TT. from the cut out the tails go into a mem 3 phase 100 amp metalclad switchfuse and from there the tails go approx 10 meters to a 60 amp 3 phase switch fuse. When I tested the earth fault loop it was 180ohm. It would be quite frightning as to what could happen if there was a phase to earth fault on any of this switchgear. I installed a new rod and got loop down to 30ohms. I have got to install a Rcd before these switchfuse.

Glad to see experianced electricians are around to fix the problems:|

 

[Apache]

Glad to see experianced electricians are around to fix the problems:|

here here!

(my house was TT'ed but the cutout is marked PME and when my CU was changed we were swapped over to the PME, Ze 0.32)

 

[batty]

here here!(my house was TT'ed but the cutout is marked PME and when my CU was changed we were swapped over to the PME, Ze 0.32)

Paddy I hope you did not do it.

 

[Apache]

Paddy I hope you did not do it.

f*** no! Proper spark, proper cert.

I fitted me loft light!

 

[green-hornet]

here here!(my house was TT'ed but the cutout is marked PME and when my CU was changed we were swapped over to the PME, Ze 0.32)

Thats the problem with PME 0.35 is an unrealistic high Ze just to cover some bottoms at the DNO.

I would presume the electrician that did your TT was not satisfied with the PME earthing and decided to better it

 

[Apache]

Thats the problem with PME 0.35 is an unrealistic high Ze just to cover some bottoms at the DNO.I would presume the electrician that did your TT was not satisfied with the PME earthing and decided to better it

Other way round!

 

[steptoe]

here here!(my house was TT'ed but the cutout is marked PME and when my CU was changed we were swapped over to the PME, Ze 0.32)

why dont you pay attention Paddy??????

*shakin head in disbelief*

why oh why would anyone want to go from a TT system to something as stoopid as a PME is beyond me.........

 

[batty]

why dont you pay attention Paddy?????? *shakin head in disbelief*

why oh why would anyone want to go from a TT system to something as stoopid as a PME is beyond me.........

There is nothing worse than a female electrician at certain times of the month

(pre menstrual electrician)

 

[Apache]

why dont you pay attention Paddy?????? *shakin head in disbelief*

why oh why would anyone want to go from a TT system to something as stoopid as a PME is beyond me.........

I didn't know then what I know now. I would have been very happy with my rod!

 

[steptoe]

I forgive you,

just this once tho.

 

[oneofthedamned]

Thanks a lot for all the comments lads I'll leave it alone then and lust RCD the first half of the board and bring him up to the 17th. I just find it strange that the previous guy left it with no RCD protection on 50% of the board when on an earth spike.