some help on cable selection

learningspark · May 30, 2011

hi all, only few months into training but keen to learn more....

i know that we use 230v for the physics but so a 9.8kw shower is:-

9800/230 = 43amp's

so what i need to know is how do we decide what size cable we use here, is it the volt drop calculation, length of run etc?

also howdens have a habit of not supplying feed cable for say a electric oven.....so a 2.2kw oven is 9.5amps.....what size flex would i put on this? would it have to be heat proof?

so my question is what size cable would i use on appliances like this?

the answer i am looking for is something like this :-

1-10amp = X
11-20amp = X
21-30amp = X

etc.........

also say if i was running a outdoor security light outside.....would i have to use SWA? i have been told flex clipped direct to brickwork is fine? someone has even said the cable used for the fire alarms!...........

i dont know alot so was looking for some very simple answers!!

thankyou

Sparky Ninja · May 30, 2011

Have you got a copy of BS7671?

p11jor · May 30, 2011

Hi there yes I have, also the OSG if that's any quicker to find it?

Sparky Ninja · May 30, 2011

With cable calculations refer to appendix 4.

Calculate the design current (Ib)
Select the protective device (In)
Collect any relevant correction factors necessary to work out the tabulated current carrying capacity (Ca, Ci, Cg, Cc etc)
Calculate It
Select Iz
Assess selected Iz for voltage drop with the adjacent tables (mv/A/M) value.

If vd is within tolerance then off you go.

Sintra · May 30, 2011

OP could you explain why you are logged in with 2 user names. By the way I have already checked the ip addresses.

p11jor · May 30, 2011

You mean my brother!?

mattmoo1974 · May 30, 2011

Sintra is a spy catcher!!!!!!!!!!!!!!
They call him Bond James O'Bond!!

mickys86 · May 30, 2011

I must admit. "learning spark" does seem very suspect. If he is genuine (brother as well lol) then fair Play for wanting to learn

learningspark · May 30, 2011

To clear this up before he goes mad, he's a spark, I have asked him for some advice on stuff before I start collage, he told me to go on this forum, we have a computor in this house that is used by all our family and I am also using his iPad as I went downstairs for tea which Is why he would of been signed in