Discuss Electrical supply to flat and block of flats in the Electrical Wiring, Theories and Regulations area at ElectriciansForums.net

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Hi all,

I am hoping for some guidance on the maximum dead calculations or a studio flatand also the block in general.

Background is I am working one a single studio flat in a block of 16, thelandlord is gradually going to redevelop the whole block and add an additionaltwo stories making a total of 24 flats. Building is standard 60’s block andbrick.


Electric is the only utility apart from water enteringthe building so all heating, cooking and water heating is going to be electric.

Incoming supply is 3 phase TNS – haven’t heard back fromWPD what the supply into the block is rated for as yet.

Each flat is served a service cupboard on that floor (notsure on the phase split as 4 floors currently) through a 60A DNO cutout andthen a 60A KMF protecting the tails which run for approx 8M at a guess(somewhere in the fabric of the building and pop out of the wall above frontdoor).

Given the whole flat is going to be electric I havecontacted WPD for an estimate as to what the building incoming will support asin my opinion from looking at Appendix A in the OSG a 60A supply won’t cut itwith the following fixed loads.

9.5kwelectric shower - 40A – According table A2 stays as 40A
3kwinstant water heater – 12.5A – stays at 12.5A
4kwelectric radiator -16.67A – diversity from A2 gives 12A
6kwelectric hob – 25A – diversity gives 14.5
2kwsingle oven - 8.33A – No diversity as under 10A so 8.33A

In addition,there will be a cold fill washing machine, cold fill dishwasher and all of the other electrical items such as kettle etc to take intoaccount but even without those my calculator makes the calculated demand 87.33A

No it isn’t exactly a large flat but there are familiesliving in some of them (two adults and a small child) although I think thelandlords target market is single occupancy.

So my question is, in the real world does the calculatednumber stack up or should I be looking at a different way of calculating things– before I did the calcs I was thinking along the lines of an 80A supply butthat number is implying a 100A supply is needed which to me seems somewhatcrazy given it’s a 35sqm flat!

Also how do I look at diversity between the flats? I knowthis is the job of WPD but it would be good to understand where they might becoming from when trying to work out overall supply into building.

If I have missed anything glaringly obvious please shoutas this is my first experience of self-contained flats and I am pretty sure Imust have missed something!!

Many thanks

Paul

 
9.5kwelectric shower - 40A – According table A2 stays as 40A =40A mcb
3kwinstant water heater – 12.5A – stays at 12.5A =16A mcb
4kwelectric radiator -16.67A – diversity from A2 gives 12A =16A mcb
6kwelectric hob – 25A – diversity gives 14.5 =16A mcb
2kwsingle oven - 8.33A – No diversity as under 10A so 8.33A =10A mcb + 10A mcb (lights) + 32A mcb (ring)

So: 40+16+16+16+10+10+32 = 140
Rule of thumb: 140 X 0.4 = 56A ( max demand with diversity per flat), so on 60A supply seems ok....


What is the supply to block of flats, cable size, type etc...
 
Last edited:
I am surprised no one on here has ever bunged on all their high powered electrical appliances and taken an actual measurement.
I just have a 9.5kw shower. Oven and CH are gas.
 
9.5kwelectric shower - 40A – According table A2 stays as 40A =40A mcb
3kwinstant water heater – 12.5A – stays at 12.5A =16A mcb
4kwelectric radiator -16.67A – diversity from A2 gives 12A =20A mcb
6kwelectric hob – 25A – diversity gives 14.5 =25A mcb
2kwsingle oven - 8.33A – No diversity as under 10A so 8.33A =10A mcb + 10A mcb (lights) + 32A mcb (ring)

So: 40+16+16+16+10+10+32 = 140
Rule of thumb: 140 X 0.4 = 56A ( max demand with diversity per flat), so on 60A supply seems ok....


What is the supply to block of flats, cable size, type etc...

Corrected, I missed that you applied diversity already, ok, so it will add extra 15A, so (140+15) X 0.4=62A (just about)
 
Last edited:
I am surprised no one on here has ever bunged on all their high powered electrical appliances and taken an actual measurement.
I just have a 9.5kw shower. Oven and CH are gas.

I have been meaning to do it for ages, but my power logger has been unavailable due to a long running dispute with a customer who's intake it is currently attached to, and has been for 18 months now.
 
I am surprised no one on here has ever bunged on all their high powered electrical appliances and taken an actual measurement.
I just have a 9.5kw shower. Oven and CH are gas.

I did put a clamp on a 9.5kW shower on an EICR once due to the cable sizing being borderline and wanting to get an exact current draw to confirm it.
The shower on full power mode drew a little over 38A as you would expect, but then after about a minute it dropped to half that as an internal thermal doodah (technical term) switched it down to only one element.

If I remember I will put a clamp on the supply to the 9.5kW shower at my parents house and see how that behaves.
 

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