16mm tails

[ambrad]

hi all

I have been to a care home to survey a bathroom upgrade and the client wants a 9.5kw shower to replace the mixer shower. The flat has lights, sockets, cooker and smoke alarm. The cu is in the cupboard and the supply and meter are in a cupboard in the main hallway. On inspection the tails to the meter are 16mm and the tails to the cu are16mm flat twin and earth and about 4m long. Firstly would you expect to see fte cable as a supply cable and secondly can these tails be split to allow for a shower unit with rcd or do they need upgrading to 25mm with an isolator. This information is to allow me not to get my fingers burnt with the price. The work will be carried out by a registered electrician.

Regards

 

[DurhamSparky]

i hate T&E tails...!!

you can keep 16mm tails and yes they can be split...

ideally i would uprate to 25 if i come accross t&E

 

[trev]

Is this so you know how much of a bill to expect? If so there are too many unknown variables EG whereabouts in the country you are, do you expect credit terms, are you likely to stick to them. All these and more will have a bearing. Best advice, get a few estimates.

 

[ambrad]

hi
yes sort of as i havent seen t & e tails before. I am aware that sparks tell me that if we add a shower the tails should be upgraded to 25mm. The client has expresses concern at this and asked if it is possible to leave the tails as they are and split the existing near the cu in the flat to allow for the new shower rcd and breaker. Just really want to have done what is correct for the client but what is also within any regulations.

thenks

 

[DurhamSparky]

for the sake of a few extra notes on the job replace the Supply Tails as if a new CU is installed just for the shower it would need to be up to current standards (25mm tails) even if it was to be split in a henley box.

 

[Engineer54]

What are these flats, one bedroom affairs?? if so keep the 16mm tails, there is no-way your going to stress them by installing a 9.5 KW shower!! Probably only a 60A fuse at cut out anyway...

I'd be more concerned with the 6mm earth in the T&E, if being used as the premises main earthing conductor. And even that may not be a problem, just don't like seeing T&E bare earthing/sleeved used as the main earthing conductor...

 

[londonlec]

No problem with a small 1 bed on 60A supply, with a shower.

 

[Farmelectrics]

surely you would have to run a 16mm earth in couldnt rely on 6mm in the twin and earth am i missing something here bs7671 states 25mm tails 16mm main earth and 10mm to water and gas

 

[IQ Electrical]

surely you would have to run a 16mm earth in couldnt rely on 6mm in the twin and earth am i missing something here bs7671 states 25mm tails 16mm main earth and 10mm to water and gas

BS7671 does not state sizes for meter tails but it states that you must comply with the requirements concerning overcurrent protection (provided by the supplier's cut-out fuse).

 

[londonlec]

Bear in mind a lot of flats will have overcurrent protection by a switch fuse or Ryefield board, meaning your tails only need to withstand the rating of that fuse.

I agree a 6mm main earth is undersized.

 

[SirKit Breaker]

I was told the other day, by someone on a course i was delivering, who works for a REC. 16mm Tails are right on the 100a cutout fuse rating limit, they are still acceptable as long as they are run in free air i.e go from cutout fuse to CU which is usually next to it, and dangling in the wind so to speak. 25mm must be used if the tails pass through any cavities, walls etc etc.

Just a little snipit for you all.

Cheers.............Howard

 

[shocking_eg]

depending if the existing board has capacity and RCD protection, if not i would install new 25mm tails from meter into a henley block, connect existing 16mm into there and come off with a small RCD DB for the shower.

 

[malcolmsanford]

depending if the existing board has capacity and RCD protection, if not i would install new 25mm tails from meter into a henley block, connect existing 16mm into there and come off with a small RCD DB for the shower.

Why are you advocating changing tails to 25mm for a small 1 bedroom flat, without knowing what the protection device is?

As this 9.5kw shower is a fixed load you could easily tail into a shower CU in 6mm which will take 47amps free to air.

 

[shocking_eg]

Why are you advocating changing tails to 25mm for a small 1 bedroom flat, without knowing what the protection device is?

As this 9.5kw shower is a fixed load you could easily tail into a shower CU in 6mm which will take 47amps free to air.

yep good point.

most pobably on a 60A ryefield anyway so 16mm could stay.

 

[Octopus]

surely you would have to run a 16mm earth in couldnt rely on 6mm in the twin and earth am i missing something here bs7671 states 25mm tails 16mm main earth and 10mm to water and gas

25mm tails and 10mm bonding is stated for new builds and rewires.

16mm tails and 6mm bonding is often acceptable, given certain situations and checks.