cable size calculations

[davedwr1978]

Can somebody please help me, what is the formula for calculating cable size, just a query not for anything in particular thankyou.

 

[Marvo]

Just refer to the tables in your OSG book.

 

[davedwr1978]

Ok, is this how it's normally done if an electrician needed to find a correct cable for a circuit at a curtain length

 

[camerabloke]

curtain length?

 

[Marvo]

Yep, that's how it's done. The same cable has varying maximum allowable load depending on how it's run (clipped surface, in conduit, buried underground etc etc) as well as how long the cable run is.

 

[Guitarist]

curtain length?

My wife always deals with curtains.

 

[amlu]

Voltage Drop Calculator

 

[SirKit Breaker]

Can somebody please help me, what is the formula for calculating cable size, just a query not for anything in particular thankyou.

If it is the protective bonding conductor size, then the formula is S= Sq root of (I squared * t) divided by k.

I appreciate that this is a DIY forum, and you are thinking "What the ell is all that about", but that is the answer to your question. And to find all the figures to go into the equation is a four day affair, we call it the 17th Edition Wiring Regs Course.

Calculating any other type of cable is also a long winded carry on, you need to know all the variables to do it correctly, and apply allsorts of correction/derating factors etc etc. Sorry to be so vague, but that is how it is, i am not trying to be clever with my answers, just honest.

To make life easier, we work a lot to standardisation, so 1.0mm cable will handle 10amps, 1.5 16a, 2.5 22a, those figures are off the top of my head, but it just an example, and again other factors need to be taken into account.

Cheers..............Howard