SWA for 2 sockets

[ajs123]

Hi,
Need to run cable outside from consumer unit to put 2 sockets in kitchen (unit at front, kitchen at rear). 1 socket dedicated to integral fridge freezer, other 1 a double on worktop for kettle. Length is approx 60ft, would a 2.5mm cable be adequate? I'm running cable then electrician to do wiring?
Been advised need 10mm but that seems overkill for these sockets?
Thank you.

 

[ericmark]

2.5 mm² will have a volt drop limit of around 44 meters with a 16 amp MCB.
4 mm² will have a volt drop limit of around 73 meters with a 16 amp MCB.
6 mm² will have a volt drop limit of around 110 meters with a 16 amp MCB.
10 mm² will have a volt drop limit of around 186 meters with a 16 amp MCB.

Note I have used Correction factor Ct to calculate these values, would be less if Ct not used to calculate.

 

[chivers67]

How big is the Kettle is it some kind of industrial one!!!

 

[ajs123]

No, just standard kettle. The electrician said 10mm swa for the double oven, then another 10mm swa going the other way for the 2 sockets we need, fridge freezer on 1, then double socket above worktop for kettle and a spare. I thought 10mm was a bit excess after a little research but am here to be advised. Thinking of finding an internal route with normal cable. Thank you for your help

 

[flameport]

The electrician

You need a new one.

Someone that can select cable sizes appropriately for the load, and find a sensible route for the cables which doesn't involve going outside.

 

[ajs123]

I have found a route which will involve trunking but better than going outside. I'll do this bit myself then get an electrician to wire it up. Would 6mm be ok for a double oven, around 5.3kw on 32A fuse? What size would I need to run for the 2 sockets? Many thanks

 

[sparkwright]

I find it almost beyond belief that in order to install just two sockets in this kitchen you need to go all the way back to the consumer unit.

If there were already sockets in the kitchen, surely you would run the new sockets from the existing wiring.

If there were no existing sockets in the kitchen, surely you would then require more than just two sockets??

One possible solution to this crazy situation MAY, and I stress MAY, be to just run one hefty SWA from the consumer unit to the kitchen, and fit a small consumer unit in the kitchen capable of feeding a hob, ovens, sockets and anything else.

I take it you are doing all of this work yourself??

 

[Astra99]

4mm² T&E is rated to carry 32A provided the cable is not derated (installed through insulation, etc). 2.5mm² cable is rated at 27A (when not derated). Thus, either 4mm² or 6mm² would be suitable for your oven/hob which is rated at 5.3KW (around 24A) and a 20A (or even 25A if your dis board manufacturer makes them) radial in 2.5mm² would be suitable for your couple of sockets. However, you may wish to furure-proof the oven/hob installation by using 6mm² cable which will support up to 47A. Many oven/hob circuits are wired in 6mm² with 32A breakers at the dis board.

 

[EFLImpudence]

4mm² T&E is rated to carry 32A

37A

 

[ericmark]

Cable type and installation method means a set size of cable has a massive range of amps rating.

As well as the amp rating we also have if the loop impedance it low enough to ensure the magnetic part of the overload will work, and the permitted volt drop is not exceeded.

So with a B32 MCB for example the magnetic part needs 5 times the current to trip to the thermal part of the trip, plus 5% allowance for volt drop, so (230/(32 x 5)) x 95% = 1.365625Ω the supply also has some loop impedance typical 0.35Ω so around one ohm for the cable.

As electricians we tend to estimate what the impedance will be, and only actually calculate when we realise we are getting close to the limit. I find the calculations are a bit of a pain, and so made myself a program to calculate it for me, which means less likely to make an error.

The hope is when it comes to actually measure the loop impedance it is within limits. Although once installed and the installation certificate has been completed there is no requirement to code if the volt drop is exceeded when doing an EICR so in real terms there are only a few appliances where volt drop is important.

Fluorescent lights with wire wound ballast and refrigeration are very voltage dependent, but little else.

Even twin and earth comes as thermal setting and thermal plastic 90°C or 70°C and we tend to use installation methods 100 to 103 so a 4 mm² cable could be between 17.5 amp and 27 amp and moving to method C 37 amp.

But at the end of the day the person who signs the installation certificate has to decide what is used and how it is run, and I don't think if I came to do a job and the customer tried to tell me my job, I would not take it kindly, so you need to consider what to say to the electrician.

 

[ajs123]

Thank you, there are loads of sockets 1 end but none at the other where the new units are going. I was going to run cable from an existing plug as it isn't used (for the fridge plus spare double) but when the electrician started on about routing a 10mm swa outside I assumed he was right as he's qualified and I'm not, but not so sure now. Thanks for all your advice.

 

[securespark]

What size MCB or fuse is on the kitchen sockets?

What floor area does the circuit cover?