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Power supply to commercial property 3 phase

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

  1. mattysupra

    mattysupra

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    Hi everyone, what is the smallest supply that would be supplied to a commercial property?
    Basically a marina but want to add caravans, so trying to get an idea if we would have enough power supplied to the actual site in first place.

    Power is provided by 3 phase and we are the only property connected to the 3 power lines suspended on the poles coming in.

    Just wondering if there would be a minimum amount supplied by the grid ? as in 100kw? 200kw etc before our CU ?
     
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  3. JohnW2

    JohnW2

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    I think that really is a fairly extreme case of a 'length of a piece of string' question :)

    Only you, maybe in consultation with others, can decide/estimate your current and possible future power requirements ...
    Your DNO/supplier will provide you with as small or as large or small a supply as you want/need (for an appropriate price). I live in an (albeit quite large) domestic house, and have a 3 x 60A (just over 40 kW) 3-phase supply. A car factory would undoubtedly have a larger supply (and would pay a fair bit more for it to be installed!) :)

    Kind Regards, John
     
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  4. mattysupra

    mattysupra

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    Thanks, im more trying to establish if there is a minimum amount of power we would have. As in, what is the smallest supply the grid would of installed. Or could it really be anything like a 30 amp supply max down the 3 phase cables coming into the building? Maybe i should be asking, is there a minimum size cable the grid would use to get the supply to the outside of the property?
     
  5. JohnW2

    JohnW2

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    Well, yes, but even supplies to domestic properties nearly always are (and have cable suitable for) at least 60A - so, in reality, I imagine that 3 x 60A (like my house, as I said, about 40 kW) is probably, in practice, the smallest they would ever install. However, subsequent 'upgrading' could well cost a lot more than having a larger supply initially, so it would be as well to try to predict your possible/probable requirements in the foreseeable future (and then probably add on a bit, 'for good measure'!).

    Kind Regards, John
     
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  6. mattysupra

    mattysupra

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    Hi, yes im doing both lol. I think i know what i need - 820 amps worked out as single phase 240v. I dont know what that would be as 3 phase? would it be divide by 3? . So that is worked out on every plug giving its maximum rated power. So diversity law i think its called comes in?

    Anyway, i have another post about that bit.

    How can i find out what the max is the grid can supply? can it be worked out on cable size? the cables are approx 15mm wide, no idea what the core size is or how you normally measure. Or is it determined by the transformer that is on the pole that the wires come out of into our building ?
     
  7. flameport

    flameport

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    In most cases 3x100A, or 69kVA.

    Ask the DNO.

    Those are certainly factors if the existing equipment is to continue in service, but all of that can be replaced so what's there now isn't particularly relevant to anything.

    What matters is how much capacity is actually needed for the installation. The new supply is then installed according to that.
    You don't design an installation based on some ropey old supply that just happens to be there now.
     
  8. mattysupra

    mattysupra

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    I hear you, for me at present, i need to attend a committee meeting where i am bringing to the table that i want to have more caravans. I know i will be hit with "we don't have enough power" which will most likely be the case. However, i hope we do have enough power for the first stage and if we do, i get it passed, we take the revenue for 2-3 years and then we can afford to increase once again along with a bigger power supply into the property. But i need to increase the revenue coming in first. If our power supply at present isn't big enough for the first stage, we are basically stuck, i cant expand and make the additional money to pay for a better supply in the future.
    So, if i can work out if it is possible, great, if not, i don't think the first stage will get passed by the committee
     
  9. mattysupra

    mattysupra

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    This is presuming that we would have to pay for the upgrade from the DNO and that they wont supply a bigger supply to the property FOC if we require it? Im presuming we have to pay them for a bigger supply installed?
     
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  11. JohnW2

    JohnW2

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    Fair enough - so you surely first need to ascertain (from your DNO) the capacity of your present supply, don't you?

    Kind Regards, John
     
  12. mattysupra

    mattysupra

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    Thanks, so get hold of them and they should be able to tell me. Would they need a site visit or will it be on record?
     
  13. flameport

    flameport

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    There is always a cost to have a larger capacity supply installed.

    If that requires network reinforcement (such as larger transformer), then that has to be paid for as well.
    Transformers are expensive.
     
  14. JohnW2

    JohnW2

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    They certainly should be able to.
    I guess that depends upon how good their 'records' are. A site visit could be necessary, but I doubt (albeit maybe wrongly!) they would charge for that.

    Kind Regards, John
     
  15. 333rocky333

    333rocky333

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    Would not the existing cut out installed give a slight indication of what may be available, I have seen 100A, 200A and 400A written on cut outs and in most cases they all apeared to have supply cables capable of that, regardless of the fuse size within
     
  16. JohnW2

    JohnW2

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    Indeed. I don't think the OP has yet really given us much information about what the existing supply actually 'is'.

    Kind Regards, john
     
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