Sub-mains to Flat, DNO supply 30meters away

[robo83]

I am looking at a job where the DNO supply is around 30 meters from the Consumer units. The SWA will be installed surface to the ground floor building up into the flats.

It is 3 separate flats, with 3 DNO supplies. I am thinking that best method would to be put sub-mains for each flat with 100amp isolator and install 25mm SWA to each CU, taking SWA at CU end into metal box then bringing cores into the CU.

I recently see a new build house where a 25mm SWA was not terminated at either end and just inside the enclosure and earthed from the banjo?

Is there a more cost effective method to this, it is a PME supply. 3 bed flat with normal accessories, electric cooker/hob (no power shower).

 

[Toneyz]

What heating is there gas/electric?

 

[Octopus]

No switch fuse?

 

[Wilko]

For me, swa is terminated with a gland. This is how the cable was designed to be used and enables strain relief, ip rating and armour earthing. Depending on max demand and run you might be able to use 16mm and 60A switch fuses at cutout.

 

[BOYD BARKLEY]

3 separate 25mm 3 core supply (swa)on 100 amp metalclad s.fuse
with 80 amp fuse . Will cater for any future load increase. PME CONNECTION AT SUPPLY END ONLY BY DNO

 

[robo83]

Thanks for all the replies.

 

[robo83]

Antony,

The flats have Gas, only electric in the flats is cooker, sockets, lighting.

 

[Leesparkykent]

You being the BNO will have to install a Ryefield or similar and a single point of isolation.

 

[J.C.E]

You being the BNO will have to install a Ryefield or similar and a single point of isolation.

is there a 'generic guide' to help do a intake with 7 flats- in terms of spacing/heights etc- i think it might be 400mm between slots in trunking for meter tails? -but a guide would be handy

 

[Leesparkykent]

is there a 'generic guide' to help do a intake with 7 flats- in terms of spacing/heights etc- i think it might be 400mm between slots in trunking for meter tails? -but a guide would be handy

Not that I know off. There's guides to say that meters should be positioned no less than 1000mm and no higher than 1800mm etc. Flame retardant meter boards are generally 11"x 8". At meter positions I generally use a 32mm bush with the in and out tails through it instead of slotting.

 

[Toneyz]

You being the BNO will have to install a Ryefield or similar and a single point of isolation.

Why a Ryefield in this case as posted three separate DNO supplies just need switch fuses in this case I think. I know where you are coming from regarding Ryefield etc in other cases.

 

[robo83]

Not that I know off. There's guides to say that meters should be positioned no less than 1000mm and no higher than 1800mm etc. Flame retardant meter boards are generally 11"x 8". At meter positions I generally use a 32mm bush with the in and out tails through it instead of slotting.

The DNO meters are roughly 30 meters away from the consumer units (external enclosure/on external wall), I was hoping to get them spaced so i can fit my own enclosure, then take the tails from the DNO into my enclosure and isolator and SWA from there to the CU.

This would cover point of isolation for each flat, the design has not been finished yet and it maybe only 2 flats. Do you have the same opinion as Antony regards the 25mm SWA, or would you go with 16mm if maximum demand permits?

 

[J.C.E]

Not that I know off. There's guides to say that meters should be positioned no less than 1000mm and no higher than 1800mm etc. Flame retardant meter boards are generally 11"x 8". At meter positions I generally use a 32mm bush with the in and out tails through it instead of slotting.

do ukpn/western want double-ins cables between head and isolator then are they happy with tri rated singles in the trunking from isolator into RB?

 

[Leesparkykent]

do ukpn/western want double-ins cables between head and isolator then are they happy with tri rated singles in the trunking from isolator into RB?

Not sure about WPN but UKPN will not accept tri rated for connection to their head. You can use tri rated from load side of switch disconnector to RB.

 

[Toneyz]

The DNO meters are roughly 30 meters away from the consumer units (external enclosure/on external wall), I was hoping to get them spaced so i can fit my own enclosure, then take the tails from the DNO into my enclosure and isolator and SWA from there to the CU.

This would cover point of isolation for each flat, the design has not been finished yet and it maybe only 2 flats. Do you have the same opinion as Antony regards the 25mm SWA, or would you go with 16mm if maximum demand permits?

Note I only posted regarding installation method, not cable size.

 

[davesparks]

I I am thinking that best method would to be put sub-mains for each flat with 100amp isolator and install 25mm SWA to each CU, taking SWA at CU end into metal box then bringing cores into the CU.


Is there a more cost effective method to this, it is a PME supply..

What are you basing this thinking on? Guesswork or calculations?

If by ‘more cost effective’ you mean ‘what is the cheapest way I can do this’ then I reckon a bit of T&E lashed in would be pretty cheap and last long enough for the cheque to clear.

 

[robo83]

Very helpful