New shower room on TT system

[piccollo]

Afternoon all, received call from builder re alterations to existing bathroom on 1st floor.

Property use to be one large house but over the years it has been changed to 2 large flats. One Basement & Ground floors & other 1st & 2nd floors, with supply & meters at 1st floor flat entrance. Here you have the consumer units / fused switch, meters & voltage operated trips. Existing wiring to lighting has rewireable fuse & no cpc’s, so decided on separate 2 way unit with RCD as main switch with 40 amp & 6 amp mcb’s. Further checks showed no Equipotential bond to Gas or Water services at point of entry. Showed this to builder & customer, O well if it’s got to be done get on with it.Noticed new kitchen had been fitted, so asked customer if they had checked gas & water , don’t know but they have added green & yellow wires & trips. Looked in the cupboard where the boiler was & noticed the supplementary bonding & rcd. Found out this was to protect the cooker, it had a 30amp rewireable fuse at the consumer unit & then the rcd next to /near the cooker switch. I was told there was another trip the other end, this protected the sockets. Looks like the ring main terminated in the rcd & the load side protected the sockets. Didn't want to pry any further.

This is what I intend doing & welcome your thoughts:-

Install a Wylex REC2s before the voltage trip [so that I have control of the supply/supplies]. Install new tails to voltage trip & fit DP Henley block after the voltage trip & reconnect existing consumer unit. Divert earth from earth rod to new earth block [MET] & install link back to voltage trip. Connect 10mm2 from gas & water services to MET & main earth to new 2 way consumer unit. Install tails from Henley block to new 2 way consumer unit. Then install 10mm2 TW & E to shower & 1mm2 TW & E to lighting & fan. No queries on this part it's the mains / supply side.

The reason I’m leaving the voltage trip [although obsolete now, is so that there is some discrimination with the 2 RCD’s in the kitchen]. I am trying not to touch the existing, apart from disconnecting the bathroom switch & light.
regards piccollo

 

[Des 56]

I have had a read through the proposal and if I am correct,you intend leaving the voltage operated elcb in situ, but also as the first line of supply/protection for the new 2-way board with its own Rcd

The re arranging of the earthing conductor to the met and back again to the elcb via a met will in effect connect together the earthing and the bonding
As far as I know, sepration of these were required to allow the correct operation of that voltage operated elcb

Where I see a problem is the rating of the elcb
Most were rated at only 60 amp.
The device being old, will already be suspect, and introducing a larger load may be a little too much for the poor blighter

 

[JD6400]

I will no doubt be told differently in a moment but i thought elcb's were as good as outlawed some 20 - 30 years ago and need ripping out as soon as you spot them ?
I seem to remember being told by one of my old foremen that i quote " rcd's trip as you get i little tingle but elcd's trip after you have had your shock and just about as you finally catch alight ! "

 

[Des 56]

Have a look at the link and question 7

Periodic inspection of existing domestic and similar installations : Electrical Safety Council

 

[JD6400]

Top job , thanks Des !

 

[piccollo]

Thanks for your suggestions & advice, you can see the problem, I thought about it & wondered where to leave the voltage trip. I know they are obsolete but I am not doing a PIR & don't want to get involved with the existing installation. As I can visualise many problems.Thats why I used the Electricians Arms section to get better advise. If I take the voltage trip out I am then leaving the lighting & other power circuits with no RCD / leakage protection. I could put the Henly block after the Wylex isolator & leave the new circuits protected by the RCD only [ no problem there ] but my new bonds to gas & water will still be connected to the earth rod as they normally would for a TT system [ or I put in my own rod]. May have to phone Technical on this for advise. Thanks again , piccollo

 

[piccollo]

Update, spoke to Technical & my Field Engineer, Going to remove voltage operated trip, remove additional RCDs in kitchen,carry out Insulation tests on other circuits, rectify if neccessary.Install Wylex isolator feeding Henley block, then Install 30ma RCD to protect the existing board & new 2 way unit with own RCD [ as previously discussed] upgrade earth to existing board, connect all earths [Equipotential, Main & Rod ] to MET. That way at least the existing is better protected & my new installation is correct. Thanks again, piccollo