Design Current

[timo]

When working out design current i know its P/V = Ib but how do you work this out for sockets?

Is a ring main just 32A

But what about a Radiel that feeds say 4 sockets, 1 spur that feeds 3 light points?

Many Thanks in advance

Timo

 

[Doomed]

you use your design current to work out your fuse rating and then cable size.
In the wiring you are talking of there are set assumptions, hence 2.5mm ring main on 32A breaker.

Please elaborate on your query, are you doing a theoretical calculation?

 

[timo]

Cable calcs really. btw sorry im a newbie so still learning allot.

Okay i know you need to work out design current before you can chose the cable size and protective device. (along with factors such as insulation etc)

I can work a shower raidel out easy enough.
example

9Kw Shower =

Ib = p/v

9000/240 = 37.5A

Design current 37.5Amps and then a suitable cable to carry that current and then a suitable MCB to protect.

But im a little unsure how you would work out the design current on a socket raidel.

If you had a raidel with 3 or 4 sockets on it with 1 fuse spur feeding 3 100watt lights how do you work out total design current on that raidel.

 

[Doomed]

Unless you know what is being plugged into the sockets you can't, hence the generalization 2.5mm 32A ring, 2.5mm 16A radial etc.

All you can do is work out the 3 x 100w lamps.

Unless as it is a theoretical college question where they want you to assume a max load per socket of 13A

 

[timo]

so really it would be 16A as the design current.

Is this what you would use on your paperwork that you give the customer along with diagrams etc when you show your workings (cals) for each circuit

 

[Romans99]

Sorry to sound like a **** but these are frighteningly basic questions to be asking.

Are you just starting an apprenticeship?

 

[timo]

Hey we all start some where, be nice to go into somthing and know everything without having to learn it

So was i right with my last reply?

 

[ian.settle1]

Cable calcs really. btw sorry im a newbie so still learning allot.

Okay i know you need to work out design current before you can chose the cable size and protective device. (along with factors such as insulation etc)

I can work a shower raidel out easy enough.
example

9Kw Shower =

Ib = p/v

9000/240 = 37.5A

Design current 37.5Amps and then a suitable cable to carry that current and then a suitable MCB to protect.

But im a little unsure how you would work out the design current on a socket raidel.

If you had a raidel with 3 or 4 sockets on it with 1 fuse spur feeding 3 100watt lights how do you work out total design current on that raidel.

As we now work to a harmonised voltage you should be using 230 in the above calculation and not 240
therefore

Ib= 9000/230=39.13A

 

[old dog]

Sorry to sound like a **** but these are frighteningly basic questions to be asking.

Are you just starting an apprenticeship?

Cable calcs really. btw sorry im a newbie so still learning allot.
he stated his experiance

 

[timo]

Cable calcs really. btw sorry im a newbie so still learning allot.
he stated his experiance

Thank you.