installing new hob

[electrician4u]

I have a customer who wants me to put in a Seimens hob. The rating is 10.8kW. he currently has a 32A supply installed from an old Wylex box-the type that takes fuses and Mcb's.this box is fed from a Bill distribution board on a 40A mcb.Can anyone suggest a make to replace the Bill MCB rated 63A?I've worked out the full load current to be 47A. According to the regs, I gather I only have to assume 10A+30% which means 21A. What if it's on full load, though? I don't want to connect to the existing 32A breaker if it's going to be tripping.Any advice please?

 

[telectrix]

10800/230 = 46.95a.

46..95 - 10 = 36.95

36.95/3 = 12.31

10a + 12.31 = 22.31a

 

[Richard Burns]

10800/230 = 46.95

46.95-10=36.95

36.95 * 0.3 =11.09


10 + 11.09 = 21

 

[GLENNSPARK]

i may have misread the diversity rule. i thought you deducted the 10A from the total then added 30% but even 30% of 47+10 is still only 24A-not a big difference, but still nobody's answered my question about what happens if the hob is on full power?
also, the mcb, although they fit on a DIN rail, are not standard cos they've no cover over the bottom terminal like most modern ones do. i've looked at the Eaton site already. it seems these are obsolete and i'm not paying £20 quid on e-bay for some 2nd hand ****.

Probably a BS3871 ....discontinued but that doesn`t mean you have to condemn it now replaced with BS60898 so just one of these if you need to up it......

 

[Jimmyb]

I always thought the new ceramic hob you couldnt apply diversity, i did clamp one once and it was pulling 40amp for 5mins so just thought it would stay like that untill the hob was turned down

 

[telectrix]

10800/230 = 46.95

46.95-10=36.95

36.95 * 0.3 =11.09


10 + 11.09 = 21

i,m old school. i use 33%.

 

[Richard Burns]

Gives a safer result so no worries there

 

[kenny7askew]

your sums are spot on so is mr burns advice,good for you.

 

[Silly Sausage]

I've worked out the full load current to be 47A. What if it's on full load, though? I don't want to connect to the existing 32A breaker if it's going to be tripping.Any advice please?

Also, if you look at the Time/Current curves for 60898 breakers, a 32A wouldn't trip for about 18 minutes on that constant load, and your cable (depending on its csa) might start getting a bit warm.

 

[ackbarthestar]

i,m old school. i use 33%.

I do love these calculations ....
What about an older cooker rated for 240V with a design current of 230V?

 

[ezzzekiel]

What kind of advice is "don't matter". If that's all you've got to offer, "don't bother".
Did I ask anyone about cable size? forget about that. It's big enough. Can anyone else answer the question I asked?

how about you learn what you are doing yourself then before you start charging customers for work then jump onto a internet forum to work out how to do it

with a chip like that i wouldnt bother giving you directions

 

[electrician4u]

think you've been on this site too long, weaselkeel.as far as i can see, you haven't offered me any advise, unlike some other, more helpful guys.
i've been an electrician for 26 years but i'm not so pig headed that i wouldn't ask for advise or confirmation on things if i need it.
chip? kettle, black?

 

[electrician4u]

in relation to the calculations on diversity, the OSG actually states for cooking appliances 10A+30% full load current so you don't deduct the 10 from 47 first

It's 10 + (30/100x47)=24.1A

The complicated part seems to be working out the full potential load for the kitchen when they've got a water heater, microwave, kettle, toaster, 8 lights,fridge, freezer,dishwasher,washing machine,hob,oven and fan! At the moment this is all fed off a 40A supply from a distribution board to a fuse box which brings me back to my original point of having to try to upgrade to a 63A.

 

[Richard Burns]

The diversity calculation is for the final circuit i.e everything in the kitchen, in this case. The current demand for the hob only is where the 10A is taken off first.
For the kitchen you have the final circuit:
The microwave, toaster, hob and oven on 10 + 30% diversity. (20A ish although your hob is power hungry)
The washing machine, kettle, dishwasher and water heater on no diversity (30A ish)
The lights on 66% diversity (nothing significant)
The fridge and freezer as total demand (nothing significant)

Have you tried using a conventional 63A MCB in place of the 40A Bill one? if they fit OK then no problem have a look at the way they fit to the busbar and see if you have an MCB with the same dimensions fixing method to connect to the busbar (and fit the cover).

 

[ezzzekiel]

If after 26 years as an electrician you require advise on installing a cooker circuit then with luck in another 26 you may be ready to move onto a two way light

 

[Octopus]

If after 26 years as an electrician you require advise on installing a cooker circuit then with luck in another 26 you may be ready to move onto a two way light

Meow!!!!!!!!!!!!!!!!!