Combining meter tails

[brennybig]

Hi all. I am replacing three CU's all with 16mm meter tails with one CU 100Amp ( conversion of three flats back into a single dwelling). Very difficult to install new 25mm tails as wiring under a tiled floor and new CU is 10 metres from the meter. Is it acceptable and are there any problems as a result of combining all three 16mm tails using henley blocks and running 25mm from the block to the new CU? I should add that all three 16mm tails have a fused 60 amp isolator near the meter.

Cheers

Brenny

 

[miner69er]

hi brennybig
the first thing to do is check the overall load expected of the new c/u final circuits.
A pair of16mm tails can take 87 Amps when clipped direct at 30 degrees ambient temp.according to my calcs! so as long as your calcs using diversity for the new circuits comes to less than 87 Amps i would personally use one pair of the 16mm tails and make safe the other pairs by disconnection or placing in their own henly blocks. the reason i would do this is because if all three are connected and some muppet removes only one main 60 amp fuse and not all three (from what you have written it reads as three seperate main fuses) then confusion rains along with charcoaled bits of muppet. One fuse, one pair of supply cables to one consumer unit.
Thats my opinion anyway.

 

[pennywise]

So you can't go around the outside of the house in SWA.

 

[pennywise]

Or alternativly going up into the floor space above and then drop down to the new CU.

 

[brennybig]

Thanks miner69er. The necessity of turning off three isolating fuses to isolate the new CU is one of my main concerns. I have considered using henley blocks on the supply side also and fitting a single switched 100 amp isolator there to overcome this problem. The dwelling has three floors, hence three ring mains plus another for the kitchen so a single 16mm tail is not an option. I am really trying to avoid the customer the expense of having to install new 25mm tails, 10 metres long in a safe zone with earthed sheating. Unless anyone knows of a 30mA time delayed RCD 100A isolator switch that I could protect the tails with?

Cheers

Brenny

 

[pennywise]

SWA all the way I'm afraid, the time and hassel making the old stuff work will outweigh the additional cost, and you wouldn't need to put the submain on an RCD. Personal opinion

 

[brennybig]

The floorspace above has the tiled floor and is joisted at 90 degrees to the direction I want to go, hence any option that can utilise the existing cables is preferable.

Brenny

 

[brennybig]

Have thought about using SWA but I still have to bury it in the wall for asthetic reasons and given how difficult it is to work with I would probably go with the earthed sheating option instead. I should add that with the exception of the supply wall, all walls involved are internal on both sides. Thanks for all your help.

Brenny

 

[High Tower]

Please don't take this the wrong way but are all the meter tails from the same origin ie are they all from the same single phase cut out and not a three phase supply split just checking as combining them would be lethal If it was the latter

 

[GStueyXR]

make sure all 3 are on the same phase :O

 

[jmtisme]

make sure all 3 are on the same phase :O

Was thinking this myself surely they are 3ph supply?

 

[brennybig]

All three isolators are fed from the same pair of henley blocks which are connected to a single phase. Oddly enough the cutout fuse holder is of the three phase variety but only one phase is being used. Perhaps in the past a phase was used for each flat each with a separate meter but that is only a guess.

Cheers

Brenny

 

[brennybig]

Onstream fitted a new smart meter at the house and fitted an isolator for free when I requested it. The new cutout fuse is 80 amps ( the fitter told me that this is the biggest they will supply now and I would have to contact the DNO to request a bigger one and explain why it is required) and they have used 16mm meter tails. Why then am I having to struggle to fit 25mm tails to the CU?

Cheers

Brenny

 

[ezzzekiel]

ah because the good ol dno dont follow the brb