Can anyone help?

What size mcb's do I need for the following

3 x Ring Mains
1 x Kitchen
3 x Lighting
1 x shower

TIA

Matt

"Matt"  wrote in message
news:422acd26$0$64728$ed2e19e4@ptn-nntp-reader04.plus.net...

> Can anyone help?
>
> What size mcb's do I need for the following


It depends, but the following might be usefull:



> 3 x Ring Mains


Usually ring mains are 32Amp, so 3 of these...



> 1 x Kitchen


What for: Microwave, small oven, coffe / tee maker, kettle?. For this I
would use a ring protected by a 32Amp.

What about the hob, electric / gas, for an electric hob a 40Amp might do...

I would also put another 6Amp non rcd protected cirquit for the fridge /
freezer, nothing worse that comming home from holiday to a thawn out fridge
/ freezer just because the immersion heater tripped the main RCD..



> 3 x Lighting


These would be 6Amp, three of these.



> 1 x shower


Depends of the power of the unit, 40Amp would give 9.6kW, 45Amp would give
10.8kW and 50 would give 12.0kW, Mine is a 8.5kW unit so uses a 40Amp...


What about the immersion heater, a 16Amp mcb would be suitable for a 3kW
unit.

And I would also put in a couple of 6Amp mcb's for the heating controller /
boiler and for the alarm...



/Morten

The most important consideration when deciding on mcb size is not the type 
of circuit you are protecting but the size of the cables conductors. For 
example if somebody had wired a ring main stupidly with 1mm cable, you would 
not be safe if you used a 32A mcb as the current carrying capacity of the 
cable would be exceeded before the breaker tripped which could cause a fire 
in some circumstances.

"Morten"  wrote in message
news:422aeb22$0$8748$db0fefd9@news.zen.co.uk...

>
> I would also put another 6Amp non rcd protected cirquit for the fridge /
> freezer, nothing worse that comming home from holiday to a thawn out
fridge
> / freezer just because the immersion heater tripped the main RCD..


You would need a 20 amp radial for the fridge. There is a large start up
current on fridge and freezers.


> > 1 x shower
>
> Depends of the power of the unit, 40Amp would give 9.6kW, 45Amp would give
> 10.8kW and 50 would give 12.0kW, Mine is a 8.5kW unit so uses a 40Amp...
>

It depends upon the cable's size, length and route.

Adam

> It depends, but the following might be usefull:
>
>
>> 3 x Ring Mains
>
> Usually ring mains are 32Amp, so 3 of these...
>
>
>> 1 x Kitchen
>
> What for: Microwave, small oven, coffe / tee maker, kettle?. For this I
> would use a ring protected by a 32Amp.


Have you been in my kitchen? Exactly that!!

>
> What about the hob, electric / gas, for an electric hob a 40Amp might 
> do...


Gas hob electric oven

>
> I would also put another 6Amp non rcd protected cirquit for the fridge /
> freezer, nothing worse that comming home from holiday to a thawn out 
> fridge
> / freezer just because the immersion heater tripped the main RCD..


No immersion, I'm on a combi

>
>
>> 3 x Lighting
>
> These would be 6Amp, three of these.
>
>
>> 1 x shower
>
> Depends of the power of the unit, 40Amp would give 9.6kW, 45Amp would give
> 10.8kW and 50 would give 12.0kW, Mine is a 8.5kW unit so uses a 40Amp...


Thanks, haven't bought the shower yet so I'll bear that in mind


>
> What about the immersion heater, a 16Amp mcb would be suitable for a 3kW
> unit.


No immersion

>
> And I would also put in a couple of 6Amp mcb's for the heating controller 
> /
> boiler and for the alarm...


Cheers

"Clodhopper"  wrote in message 
news:d0evd6$c8t$1@news7.svr.pol.co.uk...

> The most important consideration when deciding on mcb size is not the type 
> of circuit you are protecting but the size of the cables conductors. For 
> example if somebody had wired a ring main stupidly with 1mm cable, you 
> would not be safe if you used a 32A mcb as the current carrying capacity 
> of the cable would be exceeded before the breaker tripped which could 
> cause a fire in some circumstances.


So lets assume standard sizes are to be used.

"Matt"  wrote in message 
news:422b3451$0$23945$ed2e19e4@ptn-nntp-reader04.plus.net...

>
> "Clodhopper"  wrote in message 
> news:d0evd6$c8t$1@news7.svr.pol.co.uk...
>> The most important consideration when deciding on mcb size is not the 
>> type of circuit you are protecting but the size of the cables conductors. 
>> For example if somebody had wired a ring main stupidly with 1mm cable, 
>> you would not be safe if you used a 32A mcb as the current carrying 
>> capacity of the cable would be exceeded before the breaker tripped which 
>> could cause a fire in some circumstances.
>
> So lets assume standard sizes are to be used.
>

If you are sure conventional sizes are used then the answers given by others 
in this thread are correct. Never assume anything though.

> The most important consideration when deciding on mcb size is not the type
> of circuit you are protecting but the size of the cables conductors. For 
> example if somebody had wired a ring main stupidly with 1mm cable, you 
> would not be safe if you used a 32A mcb as the current carrying capacity 
> of the cable would be exceeded before the breaker tripped which could 
> cause a fire in some circumstances.


You may not think it's actually possible that somebody would be stupid 
enough to do this, but I've seen it done. Well, not 1mm but 1.5mm. We found 
this out on a recent rewire, and it's a great shame I didn't have the camera 
with me. So although MOST people would wire the kitchen in standard cable 
sizes, it's deffinitely not something that can be assumed!

David
www.dodgy-diy.net

"Bob Watkinson"  wrote in message 
news:d0fdut$7tu$1@news6.svr.pol.co.uk...

>
> "Matt"  wrote in message 
> news:422b3451$0$23945$ed2e19e4@ptn-nntp-reader04.plus.net...
>>
>> "Clodhopper"  wrote in message 
>> news:d0evd6$c8t$1@news7.svr.pol.co.uk...
>>> The most important consideration when deciding on mcb size is not the 
>>> type of circuit you are protecting but the size of the cables 
>>> conductors. For example if somebody had wired a ring main stupidly with 
>>> 1mm cable, you would not be safe if you used a 32A mcb as the current 
>>> carrying capacity of the cable would be exceeded before the breaker 
>>> tripped which could cause a fire in some circumstances.
>>
>> So lets assume standard sizes are to be used.
>>
> If you are sure conventional sizes are used then the answers given by 
> others in this thread are correct. Never assume anything though.


I'm absolutely positive, as the house was gutted about two years ago and 
rewired by a (qualified) friend. We are now having an extension built and 
adding a few circuits so need to upgrade the consumer unit.