30A induction hob and 30A oven

[sparkysean]

Hi guys I'm installing 2 new circuits for a 30A hob and 30A cooker. I'm drilling holes through joists and clipping direct, the cable run is around 25m each, i'm going to use 4.0mm? We all agree this is ok?

 

[telectrix]

fairly long run. have you calculated your volt drop?

 

[sparkysean]

No I have not to be fair there actually around 15 i'll do the math now

 

[KEVINDOE]

Hi Sean,
If It was me doing it , i think i would be using 6mm t+e on that run.

 

[telectrix]

7.8v at 30A for 20m ( 4mm cable.) but for the slight extra cost why not use 6mm.

 

[sparkysean]

thanks Jemma I would in an ideal world use a 6.0mm cable but seeing as they're seems to be people out there who will just do the work without even considering part p or any electrical safety it's forcing me to scrimp and save where I can, therefore only using 4.0mm instead of 6.0mm where it's allowed has become part of winning work i'm afraid.

but anyway here's my math:

it's 3000w so I = P/U IS

3000W/230 = 13.034a

and using mv/A/m (which for 4.0mm2 is 11) i get

11x13x25/1000 = 3.575v

the cable run is actually inly about 16m in real length i'm just adding it up rather than down, the volt drop there indiactes this can be installed legally to part p and NICEIC standards, is this correct guys?? my math and interpretation??

 

[sparkysean]

oh an sorry im also getting conflicting information about maximum volt drop allowed. I was under the impression it was 10% either side of 230v (this is what i was taught at college around 5 years ago) but i've also seen the old 10% above 4%below rule, if anybody is sure could you please clear this up for me??

 

[sparkysean]

@ telectrix how did you get 7.8v, how did you find current?

 

[KEVINDOE]

This is always the case, and always will be, theres always someone that will do it cheap , dont drop the quality of your work or you will be one of them mate.

Jem

 

[sparkysean]

Well i'm not am I, i'm ensuring it's legal am I not?

 

[KEVINDOE]

Yes , is there any insulation anywhere on route that you might have to take into account sean, just a thought ? last post wasent ment to offend by the way.

 

[sparkysean]

Nah it's an empty void beneath the floor.

cheers

 

[Deleted member 26818]

Allowable VD has never been 10% as far as I can remember.
Used to be that the supply was allowed to be 10% plus or minus of 240V. But that is now plus 10 % and minus 6% of 230V.
Allowable VD is 5% of 230V for power as far as I can remember.
Why not run a single circuit to supply both items?

 

[sparkysean]

Well it's an induction hob and oven what dyou have in mind??

 

[telectrix]

@ telectrix how did you get 7.8v, how did you find current?

you said in your op it was 30A, not 3kw, so i used 30A. max. volt drop allowd is 5% or 11.5v so you will be ok with 4mm.