What size SWA for 3 flats

[Ldix32]

Hi all,

I’ve been given 3 flats to re wire and i was looking for advice on the correct size Swa to use.

There will be 3 meters installed by the DNO, 1 for each flat. My plan was to have switch fuses after the metres and then run Swa to the DB’s. The longest run for the furthest DB is around 20 meters, the other 2 runs being 10m and 15m. The flats are all electric and no gas in the properties. Fuseboards consist of : 6kw water heater. Hob, kitchen ring, flat ring, ring for panel heaters, lights & smokes.

Would a 16mm 3 core SWA be ok to run to the DB’s or would a 25mm be better. Also would I need to run a separate earth with the armoured or would using 1 of the cores as the cpc be fine?

Any advice is appreciated.

 

[James]

Have you done any calculations yet?
what is the expected load for each flat?

 

[Ldix32]

Have you done any calculations yet?
what is the expected load for each flat?

Hi James,
Only calcs I’ve done so far were online. Recommended a 16mm but id like a few more opinions from experts like yourselves! The flats aren’t massive it’s 1 2 bed and 2 1 bed flats

Loads in the flat are :

6kw water heater
6.5kw hob
2.2kw oven
Washing machine
Fridge
X3 panel heaters per flat - x2 1kw and x1 0.75kw
Electric towel rails in bathrooms
Then just 2 ring circuits, lighting circuit and a smoke alarm circuit.

 

[James]

Less than 3kw of room heating for the whole flat?
seems unreasonably low.

are you designing, installing or doing the whole lot?

 

[buzzlightyear]

25mm SWA It's better to over size then under size., but I'm not designeing it.

 

[Ldix32]

Have you done any calculations yet?
what is the expected load for each flat?

I’ve just done a load calc and it gave me 58 amps. Would I be right in saying a 16mm 3 core swa would be fine to supply the boards

Less than 3kw of room heating for the whole flat?
seems unreasonably low.

are you designing, installing or doing the whole lot?

i said this to the project manager. I’ve been given drawings and it’s all been designed by the architect. The job is very unorganised

 

[littlespark]

Is 6kW water heating going to be ok for a bath or shower? I can see 7 or 8kW electric showers being retrospectively added in the future.

What’s the price difference of 16 against 25mm? Could be worth oversizing for future proofing.
Hardly a massive difference over the entire job.

 

[Ldix32]

Is 6kW water heating going to be ok for a bath or shower? I can see 7 or 8kW electric showers being retrospectively added in the future.

What’s the price difference of 16 against 25mm? Could be worth oversizing for future proofing.
Hardly a massive difference over the entire job.

According to them it is! I was waiting to hear back on having electric showers in the flats today but I’ve been told there going to Be thermostatic ones. To be honest there’s not much difference in price, it’s about £1 odd extra a meter and I’d be getting 50 metres altogether so I may just go for 25mm and then won’t have to worry about any issues.

 

[Dustydazzler]

I would fit 25mm SWA , you probably could get away with 16mm but when starting from scratch and you have easy access to pull in your feeds you might was well go with the bigger cable. Gives you plenty spare capacity if the owners of the flats up scale the heaters for example

 

[baldelectrician]

Remember you are limited to the DNO fuse.

Are you asking for a 100 A single phase supply, any higher and they may prefer / inisist on 3 phase?

Make sure you don't end up with the blame if the design goes wrong, insist on them providing design specs

May be better using a 16mm 5 core armour- you could have 2 cores each doubled to provice 2 x 16mm single phase or 16mm 3 phase, neutral and earth

 

[Penguin]

Hi all,

I’ve been given 3 flats to re wire and i was looking for advice on the correct size Swa to use.

There will be 3 meters installed by the DNO, 1 for each flat. My plan was to have switch fuses after the metres and then run Swa to the DB’s. The longest run for the furthest DB is around 20 meters, the other 2 runs being 10m and 15m. The flats are all electric and no gas in the properties. Fuseboards consist of : 6kw water heater. Hob, kitchen ring, flat ring, ring for panel heaters, lights & smokes.

Would a 16mm 3 core SWA be ok to run to the DB’s or would a 25mm be better. Also would I need to run a separate earth with the armoured or would using 1 of the cores as the cpc be fine?

Any advice is appreciated.

PLEASE calculate your ADMD as it’s all coming from the DNO incoming head.

 

[Other_Tucker]

For the 20m length I make it £190 for 16mm and £250 for 25mm. Are you paying for it yourself? Seems like you know the right answer and are asking 'can I get away with a smaller one'. Your thinking about it time has cost more than the difference between the two if you add it up, and the worry

 

[Penguin]

Hi all,

I’ve been given 3 flats to re wire and i was looking for advice on the correct size Swa to use.

There will be 3 meters installed by the DNO, 1 for each flat. My plan was to have switch fuses after the metres and then run Swa to the DB’s. The longest run for the furthest DB is around 20 meters, the other 2 runs being 10m and 15m. The flats are all electric and no gas in the properties. Fuseboards consist of : 6kw water heater. Hob, kitchen ring, flat ring, ring for panel heaters, lights & smokes.

Would a 16mm 3 core SWA be ok to run to the DB’s or would a 25mm be better. Also would I need to run a separate earth with the armoured or would using 1 of the cores as the cpc be fine?

Any advice is appreciated.

Don’t be pressurised and palmed off with limited unorganised verbal answers from the Designers. GET it in writing what the Electrical loads are going to be, so you can Calu your ADMD..!!
Let’s be honest if it’s an electric shower it will most prob be 10.5kw.
Washing Mc
Tumble Dryer
Dish washer
Kettle
Toaster
Hair dryer
3x Kw oil rad heaters
Coffee mc
8kw water heater

(growing recreational plants in the spare bedroom)
Get their commitment in writing for Max Demand , then use the Guide, and Future use calls.
25mm 3cSWA and I’d also consider separate 16mm Earth run along side.

It’s an over kill but at least you’ll be able to sleep knowing you’ve made SAFE.