Applying for a new supply

Dunc · Apr 2, 2012

Just in the process of applying for a new supply from the electricity board which is a completely new one for me. Just got to the part about required KVA and that's where I'm stumbling. We're applying for a 3P supply for a domestic property. Currently I've worked out the maximum demand at 215A without the garden supplies (including a swimming pool) or the gym (25A 3P sunbed, 32A 1P steam room and 2x 16A 1P aircon units) so I'm certain that a 100A 3P supply is what we'll be needing. Based on the following calculation:

(100A x 415V x 1.732)/1000=71.878KVA

would it be safe to assume that putting down a 72KVA supply on the form would be a sensible idea. Also on the tick sheet about loads that would create harmonic distortion would it be safe to assume that I can neglect telling the supplier about the heat pumps as they will all be soft start units and shouldn't create any issues.

Thanks in advance.

Knobhead · Apr 3, 2012

The soft starts will add to the harmonics, so I think you should include them.

Guitarist · Apr 3, 2012

I think if you talk to the network supplier in your area they will be far better placed to help you than us. You could even get someone out to discuss it face to face. They will also tell you what they expect from your end.

WPD Lad · Apr 3, 2012

Where are you based?

Statutory voltage is 400 and not 415, jot down 70kVA, you won't get near it unless you've got a big family that could possibly use everything at once!

Stick to 70 or less and you'll get a whole current meter which has a cheaper standing charge

SirKit Breaker · Apr 3, 2012

I used to request 23kVA when i was speccing up single phase domestic. This got you a 100a cutout fuse.
Your maths seem Ok and 70 is about right in my opinion. You will never achieve maximum demand, or if you do it will be very very rare.

Cheers............Howard

Dunc · Apr 3, 2012

Thanks guys. I did notice that I'd used the wrong voltage for my calculation, you'd have thought I'd know that having had to calculate to 400V and 230V for some time now. I've applied for a 70kVA supply but now the customer is querying if it's necessary. Unfortunately they don't understand the term 'maximum demand' or what it implies so they think that because they don't have huge electricity bills they can't be using that much electricity. I've also got the headache of balancing the phases which is neigh on impossible on a domestic install. Anyone heard of the supplier fitting two separate single phase supplies to a property. The house would sit comfortably on one and the gym, garden and pool would be fine on the other so long as a suitably small sun bed could be found.