Have I got a big problem!?

[Webby]

Hi,
i'm currently working on a project where 10 flats are being built on one side of an old silk mill. We are having a new cable put in and the origin upgraded etc. This type of work has to be done by NERS registered electricians so an outside company recommended by the DNO came yesterday and asked for what each flat will be using current wise so they can do a cable calc for the supply, which is the following.
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?

 

[Intoelectrics]

Is the incoming supply going to be 3 phase? if so the loads will be split over each phase so roughly 3.5 flats per phase.
Also you state that there is going to be 2 x RFC per flat?

 

[snowhead]

Boiler 9kw 50am breaker, ring 32a, ring 32a, oven 6.2kw 32a, heating 20a, lights 6a

If you're using those figures as is, then;

I wouldn't want to pay the electric bill for any of those flats.
And I wouldn't want to be inside any of them with all the excess heat from those appliances running flat out 24/7.

I'm sure the NERS guys are sitting down somewhere chuckling to themselves.

 

[Webby]

Is the incoming supply going to be 3 phase? if so the loads will be split over each phase so roughly 3.5 flats per phase.
Also you state that there is going to be 2 x RFC per flat?

incoming is 3phase and yes 2 x RFC per flat

 

[MDJ]

Boiler 9kw? Really do you mean shower

 

[MDJ]

I doubt you will pull 15 amps off the 2 rings

 

[MDJ]

Standard set up IME a 3 phase 160 amp supply is adequate, no problem

 

[MDJ]

Is the incoming supply going to be 3 phase? if so the loads will be split over each phase so roughly 3.5 flats per phase.
Also you state that there is going to be 2 x RFC per flat?

There can be 6 rings, irrelevent

 

[MDJ]

There is only so much that can be plugged in, a basic flat next to nothing

 

[Spoon]

Boiler 9kw 50am breaker, ring 32a, ring 32a, oven 6.2kw 32a, heating 20a, lights 6a

Out of curiosity, who specified this equipment?

 

[Webby]

Boiler 9kw? Really do you mean shower

No, its an electric boiler

 

[Webby]

Out of curiosity, who specified this equipment?

When you say equipment what do you mean?

 

[Spoon]

When you say equipment what do you mean?

Sorry, I should have been more clear.

Boiler 9kw 50am breaker, ring 32a, ring 32a, oven 6.2kw 32a, heating 20a, lights 6a

Who specified that the flats should have the above?

 

[Webby]

Sorry, I should have been more clear.



Who specified that the flats should have the above?

its an old mill and they didnt want to, or couldnt put gas in so the plumbers themselves will have supplied the boiler, like the kitchen fitters the oven/hob etc..

 

[Spoon]

its an old mill and they didnt want to, or couldnt put gas in so the plumbers themselves will have supplied the boiler, like the kitchen fitters the oven/hob etc..

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

 

[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!