markthespark

id stick a 10mm in and bang it on a 40amp breaker shud do the trick

Cirrus

Yeah, I have pulled in 10mm and ordered a 45A RCBO

Shakey

Cirrus and Grae

think you may be missing the point gents.

Firstly why would cooking the sunday dinner make any difference.? So even if its an electric hob, main oven goes on, gets up to temp, cycles on and off, some time later rings go on the boil the spuds THIS IS CALLED DIVERSITY. 61A max would be oven, grill, fan everthing, and most ovens wont let you!!! (they have this thing called a sector switch on the front!)

And Cirrus, I assume you are familiar with ring mains. So lets say you've got a small ring with 10 doubles on it. That's 26A per outlet, so that's 260A max for the ring - but you are happy to reccomend that to a customer on 2.5 mm cable???? even connected as ring thats only 54A!!! But we dont pull 260A do we? and why not? DIVERSITY

sort of knocks your 61A max into a cocked hat, dont it!!!!

Note to forum members: look up diversity in the dictionary!!! Or even BS7671!!!!

And no, i generally wouldnt use 2.5 for a cooker, because it doesnt allow for changing the appliance to a larger one later, and is cutting it 'to the wire', but it doesnt mean i would blindly throw in 6 or 10mm either

And yes you CAN get 25A Type B 60898's. Trouble is, not many people use them (or know the exist!)

And this whole thread has proved my point. Gentleman, if we also blindly throw 6mm into a cooker, 10mm into a shower and only ever use 6, 20, 32 or 40 A MCB's we get to the point where we lose the skill to actually work these things out when we need to - as proved here.

Now and again just sit down and do a calc on that circuit, before you just become, effectively, electrical labourers

i get annoyed when i see this trade dummed down to the point where anyone could size up a circuit just by reading a leaflet from B&Q or Wickes

Rant over with

And well done to Easyfox for stating a simple diversity equation that should be common knowledge

Grae79

are you working to the 17th edition then cirrus?

and as for that Shakey...possibly the most patronising reply i've read yet....well done u!

Shakey

Sorry Grae

didnt mean to patronise, i'm in crap mood because her car just failed the mot. need new discs and pads. Threw the money to the guy to get it done 'cause i just dont have the time. Then sat there for an hour and a half waiting to get it done. Then realised i could have done it myself in that time anyway, and saved myself a wodge.

And now she's onto me to clean the cooker......which is probably on 2.5mm cable

Cirrus

Well that told me! I agreew ith you on one point Shakey - it is too easy to simply get sucked in as an electrical labourer on these council rewires as all the thinking has been done for you. That is why I liked commercial and Ind work so much as it made me think. Still, rewires pay well.

Grae - I am working to 16th until June when 17th officially comes in I guess. Why?

EasyFox

Why thank you
I did have to re-read the first posts, thought it was a wind up .....or am I just sad being able to remember the diversity calc/equation

Have just read the other posts & feel a bit of a numpty because I also did the cable calcs but not knowing what the ocpd was didnt post the calcs.
Anyway I binned the idea of using 2.5mm purely on the grounds of...well I dont know why.. so a lesson learnt there, nice one shakey just goes to proove dont just do it because thats the way its always been done

So I was left with 6mm or 4mm (didnt bother with 10mm why waste money) & because I'm in business to make a profit I went for 4mm .

Well that was all hypathetical but enjoy working such things out...keeps the old grey matter ticking over, as Shakey said we can all just put 10mm or 6mm in as thats how its been done & just passed down to the next generation of sparks, & the art of working such things out is slowly being lost to your average house basher.

Thinking back to an old college lecturer he always said
"Using diversity sometimes means smaller conductors, smaller protective devices, smaller switch gear but always a bigger proffit"

Cirrus

Seems the trade is changing and not necessarily for the best

Grae79

just curious...cos you said were putting it on RCBO.

Cirrus

The council have insisted in this case because there are no spare ways in the new board on the rcd side so they want it on non-rcd but with an rcbo in place.