Discuss Armoured sub main? in the UK Electrical Forum area at ElectriciansForums.net

dksanders

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Hi All,I've just worked in a large, very old, house where the intake is in the garage, from the meter, tails go to a henley block then go through a 60A 30mA obsolete ELCB to a DP isolation switch that then feeds a twin & earth cable (looks like 16mm) which then runs 21m through the house to the laundry room, connects via another henley to another piece of T&E (unearthed!), which runs to the pantry to another henley that then feeds 3 distribution boards, and 1 sub-main off of one of those.




Apparently the intake used to be in the laundry but was moved to the garage about a year ago and an earth rod was installed by the garage (it's a TT system)


There are young children in the house, and golf clubs and tennis rackets are swung around a lot. A lot of the T&E run is within 6 ft from the floor and accessible.


My view is that if the intake was moved to the garage about a year ago, then the obsolete elcb should not have been reused, that the cable should have been run using swa (when I was there the plumber almost drilled into the cable from the other side of the wall, if I hadn't been in the room and shouted, he would have); that the cable is undersized (it is just OK for volt drop etc at 60A but given that it supplies 4 DBs supplying the large house, 21m away, I can see the elcb being replaced in the future.


It may be that as the original intake was in the laundry, that there is an earth rod going to the pantry where the DBs are, but shouldn't the earth still come from the earth rod at the garage (which is the installations earth point)?


And of course that last run of T&E should be earthed.


About 8m of the run goes outside and T&E is made to BS 6004 which states "cables for lighting and internal use". I know we've all seen security lights wired using a couple of feet of T&E but it does degrade considerably due to the UV from the sun and this is a bit different from just supplying a light.


I've raised my concerns with the customer who is trying to get hold of the electrician who did the work to get him to talk to me. I'd be grateful therefore of your views and whether I'm right or not. Thanks in advance and sorry for the long post.
 
I'm an electrician, I was wiring a new heating system that the plumber was installing.

The electrician who did the work has been working in the area for decades and I believe he's a good electrician which is whats making me doubt my own assessments.
 
you state :

"when I was there the plumber almost drilled into the cable from the other side of the wall,"

so he should have been looking then...shouldn`t he...

as creating a `safe zone`..applies to both sides of a wall....does it not.....
 
Hi Glenn, thanks for the input.

I haven't tested to see if the elcb is currrent or voltage type, the client won't be paying me for any more work than the wiring of the new heating system in place of the old one that I've completed.

Likewise I have only visually confirmed the system as a TT but it most obviously is (it's rural, in the New Forest, most are here)

The plumber had checked but he was drilling from an upstairs bedroom into the 1.5 times high utility room. There was a change in floor levels across the property of nearly 2 foot that was difficult to detect as the property is a large sprawling elizabethan house with undulating floors and levels.

The twin and earth feeder is surface run throughout it's length. It is a T&E cable which by it's very nature has a cpc buiklt into it. I've no idea which reg covers it off the top of my head but every current carrying cable has to either have the cpc or the armoured sheath connected back to the MET or it would not cause the protective device to operate in the event of the cable being damaged
 
Hi Glenn, thanks for the input.

I haven't tested to see if the elcb is currrent or voltage type, the client won't be paying me for any more work than the wiring of the new heating system in place of the old one that I've completed.

Likewise I have only visually confirmed the system as a TT but it most obviously is (it's rural, in the New Forest, most are here)

The plumber had checked but he was drilling from an upstairs bedroom into the 1.5 times high utility room. There was a change in floor levels across the property of nearly 2 foot that was difficult to detect as the property is a large sprawling elizabethan house with undulating floors and levels.

The twin and earth feeder is surface run throughout it's length. It is a T&E cable which by it's very nature has a cpc buiklt into it. I've no idea which reg covers it off the top of my head but every current carrying cable has to either have the cpc or the armoured sheath connected back to the MET or it would not cause the protective device to operate in the event of the cable being damaged


does it look like this:

imagesCALGO4BL.jpg

or this:

imagesCA0NVN5Y.jpg

is there an earth connection on it?....or not?
 
Hi Glenn, thanks for the input.

I haven't tested to see if the elcb is currrent or voltage type, the client won't be paying me for any more work than the wiring of the new heating system in place of the old one that I've completed.

Likewise I have only visually confirmed the system as a TT but it most obviously is (it's rural, in the New Forest, most are here)

The plumber had checked but he was drilling from an upstairs bedroom into the 1.5 times high utility room. There was a change in floor levels across the property of nearly 2 foot that was difficult to detect as the property is a large sprawling elizabethan house with undulating floors and levels.

The twin and earth feeder is surface run throughout it's length. It is a T&E cable which by it's very nature has a cpc buiklt into it. I've no idea which reg covers it off the top of my head but every current carrying cable has to either have the cpc or the armoured sheath connected back to the MET or it would not cause the protective device to operate in the event of the cable being damaged
have a re-think matey....
 
Just noticed the 're-think', if there was a neutral fault or disconnect then there would be just a live conductor with the only path to earth as being through the person who damages teh cable
 
As far as I'm aware you can't test to see whether its voltage or current operated, but looking at it helps.

With regards the comment about the cpc being connected, the cpc in t&e won't necessarily help in the event of cable damage . You can easily damage the cable without going near the cpc, especially if it's 16mm.
 
Just noticed the 're-think', if there was a neutral fault or disconnect then there would be just a live conductor with the only path to earth as being through the person who damages teh cable

Ok, and let's say the plumber in question clipped the cable with his drill such that it made contact with the live and not the neutral or cpc. Regardless of whether the cpc is connected or not he's still going to fry!
 
As far as I'm aware you can't test to see whether its voltage or current operated, but looking at it helps.

With regards the comment about the cpc being connected, the cpc in t&e won't necessarily help in the event of cable damage . You can easily damage the cable without going near the cpc, especially if it's 16mm.
looking at it would confirm.

their pretty obvious....
 
you say you`v only carried out a visual for TT.

A Zpe and a Zpn will/should confirm this for a start...

as often you`l find something that was TT and has now been brought onto distributers facility the main earthing connection to the rod will have been left in place....as the rod would have now become an extranious conductive part...so now that main earthing to it will have become a bonding conductor...will it not?...
 

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