Correct cabling for flat consumer unit supplies

[James McDonough]

I'm after some advice please guys..

I've got a job where the builder is converting a shop and flat above into 3 separate flats. There is currently just a 100a single phase supply into the shop on the ground floor.

I have requested a new three phase supply to be installed, which will be located on the ground floor and will eventually be the hallway for the 3 new flats.

So in the hallway will be a three phase supply and three meters (one for each flat). I then need to run a cable from the meter to the consumer unit in each flat and trying to work out the best way to do this.

Has anyone done this before as has any good suggestions?
The supply cable for each flat will ideally have to be inside the wall and floor at some point so if I use t&e it will require a 30mA RCD. Which will then cause issues because it may trip before the consumer unit RCD. Also thought about using a time delayed RCD but I can't seem to find a 30mA version out there.

Thanks in advance!

James

 

[Deleted member 26818]

Whilst there are a few time delayed 30mA RCDs out there, it would not be acceptable to use one in the situation you describe.

 

[SparkyChick]

Switch fuse for each flat feeding a 16mm or 25mm (depending on suppliers fuse) 3 core SWA. Put the earth in the cable, earth the armour at the origin of the supply.

Terminate in a 2 gang back box behind the CU and bring the supply in from the back, or just terminate directly to the CU.

That's how I'd do it

 

[westward10]

No such thing as an s type, 30ma rcd is there? As SC says swa cable suitably glanded at both ends.

 

[Electric Magic]

Switch fuse for each flat feeding a 16mm or 25mm (depending on suppliers fuse) 3 core SWA. Put the earth in the cable, earth the armour at the origin of the supply.

Terminate in a 2 gang back box behind the CU and bring the supply in from the back, or just terminate directly to the CU.

That's how I'd do it

Good advice. Although you can size the cable based on the size of the fuse in the switch fuse rather then the supplier's fuse.

 

[Deleted member 26818]

No such thing as an s type, 30ma rcd is there? As SC says swa cable suitably glanced at both ends.

I believe some Chinese companies produce them.

 

[The Ghost]

Something like this??? Those Hager are cam lever HBC fuses.

 

[The Ghost]

P.S. not my work.

 

[KEV 1 N]

We did some flats several years ago, where the main supply and meters were located in the basement. We ran a split concentric cable to each flat

 

[westward10]

That requires additional rcd protection if in a wall without earth containment.

 

[Andy78]

SWA would be my option too. Saves having to use extra protection against impact or other measures to avoid having to RCD protect the distribution circuit.

 

[Octopus]

Switch fuse and swa is the only option

 

[westward10]

The easiest option but not the only solution.

 

[KEV 1 N]

The flats were done in 2006, so rcd protection wasn't required.....SWA is the best way to go, may be cheaper to run a seperate earth cable along side 2core swa as opposed to buying 3 core.

 

[dinger809]

Did this a couple of months ago. Three phase supply into Ryfield Board and then each individual supply out, through meter, isolator switch and to each flat using 3 core armoured.

 

[Deleted member 26818]

Of course, if the Gas and Water are supplied in plastic, there would be no need for a separate Earth conductor.

 

[Leesparkykent]

This will come under what's called a Building network operator installation. The DNO will give you guidance on what they want but a single point of isolation for the building will be needed and a ryefield board or similar so it can be sealed. Normal layout is head, fused switch or isolator depending on the distance, ryefield, Meter, switch fuse or isolator them armoured cable to the flat. You have to get it all in place leaving the connection ready for the DNO to connect in to the head and have the tails in place from the ryefield to the meter and from the meter to the switch fuse/isolator ready for the meter operator to connect.

 

[Leesparkykent]

Of course, if the Gas and Water are supplied in plastic, there would be no need for a separate Earth conductor.

you can't run plastic gas pipes in a building as it would be catastrophic in a fire. If the gas is run in plastic externaly it has to change to be being metallic before it enters the building. The yellow plastic pipe feeding external gas meters is not allowed to be exposed so again needs to change to be being metallic before it comes out of the ground.....in other words it's pretty hard to get away with not bonding gas.

 

[dinger809]

This will come under what's called a Building network operator installation. The DNO will give you guidance on what they want but a single point of isolation for the building will be needed and a ryefield board or similar so it can be sealed. Normal layout is head, fused switch or isolator depending on the distance, ryefield, Meter, switch fuse or isolator them armoured cable to the flat. You have to get it all in place leaving the connection ready for the DNO to connect in to the head and have the tails in place from the ryefield to the meter and from the meter to the switch fuse/isolator ready for the meter operator to connect.

I wish I’d taken a bit more time in my reply, but that is exactly what I did! Thank you for the perfect explanation

 

[Ian1981]

This will come under what's called a Building network operator installation. The DNO will give you guidance on what they want but a single point of isolation for the building will be needed and a ryefield board or similar so it can be sealed. Normal layout is head, fused switch or isolator depending on the distance, ryefield, Meter, switch fuse or isolator them armoured cable to the flat. You have to get it all in place leaving the connection ready for the DNO to connect in to the head and have the tails in place from the ryefield to the meter and from the meter to the switch fuse/isolator ready for the meter operator to connect.

Would you need a switch fuse after the BEMCO or ryefield as you call it? or just from the BEMCO via meter and double pole isolator as you would have potential say 2 60 amp fuses in series and it’s a different set up to say a house where the tails are greater than 3 meters and is the origin of the supply?