Diversity law i think its called? how do you work out or estimate power required?

Discussion in 'Electrics UK' started by mattysupra, 23 Jan 2021.

  1. mattysupra

    mattysupra

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    I think its called diversity law? What would an estimate be of how many amps / kw etc we would require for the following please?


    Clubhouse = 100 amps

    15 caravans @ 16 amps (16 amp blue 240v plugs) = 240 amps

    30 boats @ 16 amps (16 amp blue 240v plugs) = 480 amps

    Total MAX = 820 amps = 197 KW single phase ?? (i think that's correct)

    In reality only 50% of boats and caravans will be in use at one time. They all wont be pulling full power at once either, is there a guide of what support of supply power we would need?

    thanks
     
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  3. SUNRAY

    SUNRAY

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    Heck I'm out of date. Camping site sockets used to be 5A or 6A.
     
  4. flameport

    flameport

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    Correct but only if all of those outlets are at their absolute maximum at the same time (they won't be), and if the nominal voltage was 240, (it isn't).

    3x100A / 69kVA will probably do for the whole lot, which is approximately 1.5kVA average per caravan/boat.
    The 16A outlets won't be individually rated for 16A either, 10A would be more usual.

    However all depends on what these boats and caravans are. Substantial differences between Sunseekers / Winnebagos and the rusting contraptions that spend most of their time blocking the front windows of the owners house with occasional outings along narrow country lanes at 6mph.

    Clubhouse depends massively on what's in it, and specifically whether any heating/cooking items are electric or gas. In any case, exceptionally doubtful it will be anywhere near 100A.
     
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  5. JohnW2

    JohnW2

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    It's correct if you assume 240V. We normally calculate on the basis of the UK 'nominal' voltage of 230V, in which case its around 187 kVA
    If you're fairly sure of that, it halves your calculated 'maximum possible demand' for a start.
    That's a very 'industry-specific' question - you would probably have to look around the caravan/boat community to find ideas, guidelines or rules of thumb. As an 'outsider', I would try to even hazard much of a guess - but even the 50% of boats in caravans in use at one time will obviously not using 'full power all the time', so a realistic figure would certainly be appreciably less than the calculated 'maximum possible'.

    Kind Regards, John
     
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  6. SUNRAY

    SUNRAY

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    100A 3 phase is probably all you'll ever be allowed without an expensive installation cost and as Flameport says sounds like it will suffice.

    Let's put some sort of proportion in this.

    The average consumption of my house over a year is around 4000KVA or about 10KVA per day averaging that over 10 hours is 1KVA or about 4A.
    Being realistic, this includes an electric shower, washing machine, tumble dryer, dishwasher, electric cooker and I know modern campers/boats are better equipped than when I camped in yesteryear but I find it hard to believe they will exceed my 4 bed house.
    Let's say you have 30 units at that 4A and your 720A calculation is only 120A. All of a sudden 2x 100A phases for hookups is looking much healthier.
     
    Last edited: 24 Jan 2021
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  7. mattysupra

    mattysupra

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    LOL, ye mix of sunseekers and rust buckets. The caravans are all modern and carvans, not motor homes.

    At present the caravans all have a 16 amp supply which in reality is more than they need, but they are the newer part with electric upgrade last year (only have 5 caravans at present)

    The moorings are on old electrics, no idea how old as before i was around, but all have 16 amp socket but some feed by a 10amp mcb, others 16 amp mcb, some sharing a 16mcb etc. But as the newer boats arrive, the more power they want. My next stage is to get 32amp connections installed. But as said on another post, i have to do this in stages. I know that when we get to 32amp supplies i will need the DNO to upgrade incoming supply. Its all about what i can do with what we have at the moment and get the place earning some money to pay for future upgrades.
     
  8. mattysupra

    mattysupra

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    Biggest issue with boats is the heating. My personal boat has 2x 32amp connectors i have to plug in. 1 for heating, 1 for the actual boat. As you will know, its the surge of power at the start, once up to temp etc, then fine. My boat i tried to run on a 16 amp convertor, the heating pops the breaker straight away, has to be in a 32 amp socket. But once up to temp, it will then run on a 16 amp supply. Also, most boats no longer have gas, so cooker, microwave, oven etc is electric.
    As most boats get used at weekend, people turn up and turn on -
    Water heater - 3kw
    Heating - 3kw (mine has 9kw AC unit)
    Kettle - 3kw

    so most can ask for 9kw easy. However, most know this isn't possible so they turn one thing off and turn another on. But like i say, once all up to temp, the power is low, its the surge at the start for 15 minutes or so.
     
    Last edited: 24 Jan 2021
  9. SUNRAY

    SUNRAY

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    All understood, I used to live near a touring caravan park of about 40 pitches, this was around 1980 and the sockets MCB's were rated 5A, total supply was 100A and included shower/toilet block with electric showers and hand driers and a shop/office with fridges/freezers.
    I'd get a call most weeks in the summer but virtually all related to driving off without unplugging.
    I currently assist at a scout camp site but the electrics are in no way designed for the sort of usage of yours, in fact 2 pillars on 32A supplies with 4x 16A MCBS/sockets each and of the rare occasions they are used it tends to be a cable feeding 4 or more units.
     
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  11. JohnW2

    JohnW2

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    If people switch on loads which cause their local breaker to trip, that's obviously their problem - and, as you suggest, they have to practise 'usage management' to address that.

    However, the kettle will only be on for a very short time and the water heater will presumably only draw 3kw continuously for a relatively short period of time until the water is 'up to temp' (and the same may well be to some extent true of the heating, particularly in warmer weather). Considering that, and also the fact that people will presumably not all not turn up and switch all those things on simultaneously, it wouldn't surprise me if, even during that 'turning up period' the demand averaged over all the boats was less than half of what you fear.

    Kind Regards, John
     
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  12. Simon35

    Simon35

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    Pedant alert.....kVAh or kWh.....
     
  13. Harry Bloomfield

    Harry Bloomfield

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    A 16amp MCB is the normal rating now. I have a 3Kw heater, blown air fan, 750w immersion, fridge freezer, battery charging, 21 lamps, water pump, sat system and TV. Some have microwaves and electric kettle.

    During a summer weekend, all pitches are normally filled.
     
  14. raykf

    raykf

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    The DNO calcs. for new supplies to UK domestic housing:

    UK Power Networks would in general expect the (ADMD - after diversity
    maximum demand) for a gas heated flat/house to be between 1.5kVA and
    3.0kVA and an electric heated flat/house to be between 5kVA & 10kVA
    unless abnormal high usage appliances are being installed.
     
  15. SUNRAY

    SUNRAY

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    My apologies and I'm totally surprised that I got this wrong. KVAh but of course the more usual domestic term KWh.
     
  16. JohnW2

    JohnW2

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    Indeed - but, as you say, those figures relate to domestic houses, whose consumptions will generally be a lot greater than the boats/caravans which interest the OP.

    Even if one ignores the fact that many/most of the caravans and boats will probably have some 'electric heating' and goes with the 3.0 kVA figure, that much each for the OP's 45 boats+caravans would multiply up to a frighteningly (and expensively, and unnecessarily) high total!

    Kind Regards, John
     
  17. JohnW2

    JohnW2

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    True - but although it's probably not true of the OP, "KA" "VA" probably means nothing to most of the people who ask questions in this forum, and an even higher proportion of the 'general public' - and, for the purpose of the discussion the difference between kW kWh and kVAh is of no consequence.

    Kind Regards, John
    Edit: typos corrected. Apologies!
     
    Last edited: 25 Jan 2021
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