New elec supply power 6 bed student flat, 80A enough?

[bobbybo]

Am building a block of 6 flats, each with 6 bedrooms per flat, could use advice rom electric engineer or consultant or experienced spark if a 3phase 80A supply will be enough per flat?

the flats are HMO so for 6 beds we need to provide 2 hobs, and two ovens, one 8.5kw elec shower and other shower off white meter/night storage cylinder, is a Passivhaus insulation standard throughout with Triple glazing and MVHR heat extractor duct system which uses less power than low energy bulb, so heating demand should be next to nothing

Loadings per flat will be:

1no 8.5 kw electric shower.

1no 3kw unvented cylinder. night storage white meter

2no induction hobs appx 2.8 kw

2no electric ovens appx 2.5 kw

6no electric heaters appx 0.5 kw each - 3kw total

1no small heater in lounge are 1 kw (assumed, but might not be required)

1no heat recovery system, low power

6no rooms in each flat, low power usage.

[iphonedyou]

Can't help, but out of interest (and speaking as a QS) do you not have M&E consultants on board?

Genuine question!

[bobbybo]

I have a company doing the water installation which comes in same route as electrical who are knowledgeable, would like another opinion as their engineer is not long started, no gas in the flats just electric and water..

thanks for reply!

[bobbybo]

I have consultants just prefer a few opinions and discuss before move, can you stop posting if you have nothing positive to say

[iphonedyou]

bobbybo said:

I have consultants just prefer a few opinions and discuss before move, can you stop posting if you have nothing positive to say

So you DO have M&E consultants? OK.

Genuinely - ask them. They're insured to advise you, so you have fallback if they get it wrong, but they're also qualified and know your project so will invariably be correct.

[caziques]

I would be fitting a hot water heat pump - and forget the electric shower.

400-450 litre cylinder with say a 6kW heat pump (that draws 1.5kW). By far the cheapest way of providing hot water if there is no gas.

(I would also install water pipes in the slab if it has one - and use the same hot water heat pump to provide space heating).

(The cylinder will still need an element fitted to take the water to 60c at night).

[simonre7]

3phase 80A is 57kW of power so if it’s only serving the loads you have listed (21kW) plus 6 bedrooms i’d say it’s excessive. At a guess, you’d only draw about half of that with diversity.

[KevinCamaroSS]

Not sure why you would want 3-phase in each flat? I would look at 3-phase into the block then take two flats off each phase so that it is reasonably balanced.

[grumbas]

Assuming that's 80A single phase then it doesn't seem enough.

230V x 80A = 18.4KW

Your loads above come out around 20-21KW if all maxed out (unlikely and I believe the regs allow for this scenario?).

Personally I'd be installing 100A (which seems fairly standard) to give a bit of headroom/future proof. I can't imagine cost would be that different, slightly thicker cable but I'd imagine most of the installation cost comes from labour/groundworks etc?

Note - not at all qualified, so get proper (insured) advice as already stated!

[bobbybo]

thanks for all replies, slow in reply with joys of site management!

am awaiting reply from Consultant (Lloyds accredited), the 3 phase supply will be split and each flat recieve single phase, the initial budget design was 30a per flat, the Power company upped it to 50a in more detailed design quote as 6 bedroom flats with effectively two kitchens as per HMO regs, so drawing more power than standard units, my spark is flapping about fuses blowing and wanted 80a per flat , he has added everything together and assumed worst case scenario , but has not added diversa per flat & not a consultant, i think he has upped it too much to cover himself from problems in future but im not an expert..

is 50a per flat enough?, yes i know i need a consultant who i have instructed, but just like a few opinions and PH has some talented people, used to get great advice here for my TVR S2 and then for business stuff after that and has been fantastic, majority not 'internet randoms' as has been said!

cheers