Improve a bodged garage supply.

[SparkusMaximus]

Hi all,

My mother in law has a gagarage converted into an annex, a lot of bodging has taken place all before I knew them.

Inside the flat conversion we have a 9.5 kw shower on a 32a, a ring on a 32, light circuit on a 6a and a water heater on a 16a,

Now the SWA supplying this is 6mm protected by a 32a mcb on the rcd protected side of the CU.

I said I would sort it out for them as when they have the shower it will trip sometimes as they use a plug in heater.

I want to obviously change the cable, but working out my MD its looking like I need a 16mm this will be a nightmare so can 10mm be justified?

CC of 10mm swa ref method C is only 58a table 3 (three core as I need to transport the earth)

Do I need 16mm or will 10mm sufice.

Thanks guys I really appreciate your help as I want to be able to work things out the BRB way.

 

[Guest 004]

look up cable clacs, there is a thread going

 

[malcolmsanford]

So your thinknig is that you will need a 60amp supply to feed thse 4 circuits .................... I would say that 40 amps would be more than efficient, if you don't think it is then you could get a 50amp, but remember entirely houses run quite happily on just 60amps.

 

[Guest 004]

Just done a quick calc on Amtech, it is coming back at 35mm, that 9.5 Kw is the problem, plus another 13Amp heater

 

[telectrix]

10mm XLPE SWA has a ccc of 81A ref. method C , clipped or buried. will be adequate for your needs, ( ref. AEI Cable Finder , online )

 

[SparkusMaximus]

Well thats what I am thinking logically, but when I do the MD it comes out at about 90a, I know they will not pull that but and a 10mm will be an improvement but, shower will be 41a although its on a 32a mcb which never trips only the the mcb in the house goes for the whole lot.

and I don't think I can put it on a 63 as the ccc is only 58 for a 3 core swa ref c or have I got that wrong?

 

[SparkusMaximus]

Thanks telectric I did see the XLPE thread but thought that value was only burried, didn't realise it was for ref c too.

 

[telectrix]

as i said 10mm XLPE on a 63A be fine.

 

[Guest 004]

Volt drop!!

 

[SparkusMaximus]

TBH I have not done any volt drop calcs yet run will be about 15m

 

[Guest 004]

View attachment Garage Supply.pdf

Print out from Amtech, with 3% VD, you will need a 25mm, for a 50 Amp supply
2% gave a 35mm

Shower has no diversity allowed 41 Amps @ 9.5Kw
and you have a 3 kw heater as well

 

[Guest 004]

so you 80 meters to the DB, and 15m to the shower?

 

[SparkusMaximus]

SWA supplying the annex from the main CU is about 15m.

 

[Guest 004]

ouf, dont know where I got 80 metres from, BRB with a calc for 15m

 

[Guest 004]

10mm for 15 m