What are my options?

[NozSpark]

I was at a job today (PIR/fault finding) it's a TT installation and the tails go into a kmf switch fuse and from there 16mm T&E in through the wall, up the inside (burried direct), through the loft (clipped to a purlin) and then down behind the plaster to the CU. The CU is a dual 30mA RCD board (Volex,,, pah)and they've put the main switch right in the middle:O very odd configuration IMHO!

Now the problem is that the incomming sub main has no RCD protection, it's a TT installation and the cable is burried <50mm. Realistically the cable needs 30mA protection, but I can't do that due to discrimination.

Is my only option to replace the T&E with SWA and give it a 100mA TD RCD at source? Or is there another way?

 

[Andy™]

stick some steel plate over the cables? done that a few times with 1.5mm galv

it will at least get you out of 30mA RCD, but you would stil need another TD type at the meter

 

[steptoe]

steel plate, though Im not sure 1.5mm would be enough, an sds would be through it pretty fast, but it would work as an earthed shield, even if not as a stopper!

Ive used 3mm in the past, bonded to MET of course,

and as Andy says, still need a 100mA TD up front.

 

[Andy™]

steel plate, though Im not sure 1.5mm would be enough, an sds would be through it pretty fast, but it would work as an earthed shield, even if not as a stopper!Ive used 3mm in the past, bonded to MET of course,

and as Andy says, still need a 100mA TD up front.

it may be 2mm galv plate (got loads of it lying around). either way, an SDS will not go through. i tried it after i used an HSS bit to make the fixing holes

also, there is no requirment to earth it (although ive only ever used it for tails, and it did get a bit of 10mm to it

 

[steptoe]

Im corrected then,

shoulda known youd been trying that!

after all, look at some of the other crazy stuff you try out!!

---------- Post Auto-Merged at 21:37 ---------- Previous post was made at 21:35 ----------

there is no requirment to earth it

as long as you are confident the mech properties are adequate,

and, like you say, for tails its not usually that difficult to throw a bit of 10mm at it.

 

[Andy™]

Im corrected then,shoulda known youd been trying that!

after all, look at some of the other crazy stuff you try out!!

---------- Post Auto-Merged at 21:37 ---------- Previous post was made at 21:35 ----------

as long as you are confident the mech properties are adequate,

and, like you say, for tails its not usually that difficult to throw a bit of 10mm at it.

well i had to make sure it would be upto the job

and what do you mean 'crazy stuff' i try out?!

 

[NozSpark]

Cables already in wall and decorated house mate

Thought that I'd sent that

Anyway I guess that I wouldn't need to rewire in SWA, I could use T&E in trunking:| with 100mA TD RCD

 

[Apache]

How realistic would it be to move the CU to where the KMF switch is?

 

[NozSpark]

The KMF switch fuse is inside the meter cabinet,,, so no chance I'm afraid

 

[kme]

Got 52 local flats with similar arrangement - either 16mm FTE or tails in the walls, from communal hallway to each flat. Landlord wouldn`t pay for 52 no. 100mA TD RCDs - so they`ve stayed like that.

Added isuue being that the TT earth for eaqch flat goes to the flat independently - there is no CPC or earthing system at the KMFs

 

[steptoe]

HOLY MOLY KME,

and what edition was that OK in?

Im trying to work out how you can get the KMFs earthed and comply, but without 100mA Im stumped,

OK, so the feed wouldnt comply, but that is sounding weird to me,

:C

 

[Sharpend]

That does sound strange.

Are sub mains run in conduit which may have been earthed originally then at some point the sub mains have been upgraded hence the separate earths? What are the earths connected to at the service head end?