Have I got a big problem!?

[davesparks]

Boiler 9kw 50am breaker, ring 32a, ring 32a, oven 6.2kw 32a, heating 20a, lights 6a
This is then multiplied by 10 for the ten flats. Looking at diversity tables theres a strong possibility diversity cant be applied unless we could use column 2, heating & power - If not the cable size is going to be ridiculous as it needs to be in trunking, ratings go down etc.. What are peoples thoughts?

Why do you say there's a strong possibility diversity can't be applied? Over 10 dwellings diversity can definately be applied!
Your loadings seem very odd to me, it's almost as if you've counted the ratings of circuit breakers instead of actually calculating Ib.

If you've got a 9kW boiler why do you need another 20A circuit for heating?

 

[Bobster]

I think you need a better electrical contractor.

Although diversity for a block of flats isn't exactly beginner stuff, the information you have provided (I presume has been provided by you by the contractor you've employed) is pretty duff.

 

[Webby]

Why do you say there's a strong possibility diversity can't be applied? Over 10 dwellings diversity can definately be applied!
Your loadings seem very odd to me, it's almost as if you've counted the ratings of circuit breakers instead of actually calculating Ib.

If you've got a 9kW boiler why do you need another 20A circuit for heating?

they are breaker ratings and the 20a for heating is just a radial going to a potterton economy 7 controller for controlling the boiler. I wondered if there was a diversity figure you could apply to there being 10 flats, its not something i have seen as yet though, thanks for the reply

 

[Webby]

I think you need a better electrical contractor.

Although diversity for a block of flats isn't exactly beginner stuff, the information you have provided (I presume has been provided by you by the contractor you've employed) is pretty duff.

According to you it is...

 

[Webby]

Ok, so the boiler & oven/hob are already fitted?

yes already fitted thanks for your replies!

 

[Bobster]

According to you it is...

An to you, they are providing good advice and calculations?

Reason for you starting the thread then?

 

[davesparks]

they are breaker ratings and the 20a for heating is just a radial going to a potterton economy 7 controller for controlling the boiler. I wondered if there was a diversity figure you could apply to there being 10 flats, its not something i have seen as yet though, thanks for the reply

Then you need to use the design current, not the mcb ratings, the reason for this is hopefully obvious.
This 20A heating circuit is a good example, it has a 20A mcb but the only thing connected to it is a timeswitch which will use a fraction of an amp. Over 10 flats that's 200A if you add up the mcb ratings, or maybe 2A if you add up the actual load.

 

[Webby]

Its ok, i have sorted it, thanks for mostly everyones helpful replies

 

[MDJ]

I doubt the flats will pull 45 amps on average on a good day

 

[Intoelectrics]

There can be 6 rings, irrelevent

Never said it was,

I was just curious... i.e I assumed one for the general sockets throughout the flat and one for the kitchen? Is it a bedsit type flat...etc? I was hinting at the design spec of the install.

 

[Spoon]

Its ok, i have sorted it, thanks for mostly everyones helpful replies

Glad you got it sorted mate.
Next time it would be better to chat to an electrician and you can go through the design and what is needed together, rather than just bypassing them.
Every day a learning day...

 

[naylorpd]

Oven and hob for 6.8kw seems a bit light. Whilst modern ovens can just about run on a 13A plug (say 3kw), a typical 4 ring induction hob will be rated up to about 7kW.

 

[davesparks]

Oven and hob for 6.8kw seems a bit light. Whilst modern ovens can just about run on a 13A plug (say 3kw), a typical 4 ring induction hob will be rated up to about 7kW.

You need to apply diversity to the load.