New Supply!

[hoppy]

Hi,

House I am working on s having a new sp & n supply installed. As a result the new incomer will be approx. 15 meters away, so I need to run a sub main.
Main fuse is 100A so was thinking of putting an 80 amp sub main with 25mm 3 core swa. But got me thinking Is this over kill ad would a 60A sub main with 16mm 3 core swa suffice.
Usual loads of shower 9kw, cooker, micro oven and elec hob, utility room. Normal lighting and socket layout.
Calcs for diversity over 60A, but experience says 60A should be ok.

Customer is running a tight budget as usual!

What do you guy think, 16mm 60A sub main or 25mm 80A?

 

[dingledong]

Why Re they fitting their head 15 metres away and that seems a big house

 

[hoppy]

New supply due to fault on existing, relocation of main head due to new extension being in way, and 15 meters is around part of the house!

 

[Baker1988]

if the calcs are saying put over 60A in then i would just put the 80amp in with 25mm, but that might just be me

 

[atm84]

Work out the max demand including diversity also allowing for 30% spare capacity. See what you come out with.

 

[Octopus]

Is there much difference between 16mm and 25mm SWA? £2.50 per meter maybe - so for a difference of about £40.00 I'd recommend the 25mm

If they can afford a big extension, then about £40.00 isn't even a drop in the ocean!

 

[Spoon]

I'm with Murdock on this one. For what its worth, go with the 80A.

 

[telectrix]

If ref. method C, then 16mm on 80A is best of both worlds.

 

[D Skelton]

Errrr????

16mm is good for 80A.

FFS!

 

[Engineer54]

Errrr????

16mm is good for 80A.

FFS!

You got there first!! ...lol!!

Depending on the installation reference methord used, a 16mm SWA cable can be good for well over 100A!!

 

[HappyHippyDad]

You got there first!! ...lol!!

Depending on the installation reference methord used, a 16mm SWA cable can be good for well over 100A!!

Could you expand a bit please E54? 97A is the highest CCC I can find for 2 core 16A SWA ref method E - in free air.

Plus the chap says he is using 3 core so ref method E shows 83A.

 

[Engineer54]

In my manufactures cable data, it rates the CCC at 110A. Another reason why i rarely if ever use the cable CCC in BS7671...

 

[Simonslimline]

Could you expand a bit please E54? 97A is the highest CCC I can find for 2 core 16A SWA ref method E - in free air.

Plus the chap says he is using 3 core so ref method E shows 83A.

Table 4E4A (page 348)

Only line & neutral carry current so no need to include the earth core. So 1 two core cable single phase AC reference method E 115Amps CCC. Thats thermosetting at 90C though.

probably irrelevant anyway as the connected equipment wont be rated for 90c

Could be wrong however?

 

[HappyHippyDad]

In my manufactures cable data, it rates the CCC at 110A. Another reason why i rarely if ever use the cable CCC in BS7671...

Thanks..

 

[Andy78]

Could you expand a bit please E54? 97A is the highest CCC I can find for 2 core 16A SWA ref method E - in free air.

Plus the chap says he is using 3 core so ref method E shows 83A.

As Simon says ^
You were using table 4D4A .... this is for PVC/PVC/SWA
Table 4E4A is for XLPE/PVC/SWA ..... The vast majority of (decent sized) SWA cable nowadays is XLPE

 

[Engineer54]

As Simon says ^
You were using table 4D4A .... this is for PVC/PVC/SWA
Table 4E4A is for XLPE/PVC/SWA ..... The vast majority of (decent sized) SWA cable nowadays is XLPE

Think you'll find that PVC/SWA/PVC is mainly special order now in the UK. Though i expect some wholesalers will still keep it in stock until such times as it's not being purchased in sufficient quantities to keep it a viable stock item....

Oh, and i did state the 70C CCC rating i gave above. The table gives both. It'll be as rare as hens teeth to be working on an system that warrants and complies to a 90C installation etc....