calculating power requirements for a new build house

[Galfredus]

Hello All.

I'm new, but I've searched for an answer to this and can't quite find it. I'm building a new house and need to get en electrical connection. EDF energy wants to know projected power requirements in the form of Kilo-Volt Amps, which I understand are broadly comparable to Kilowatts (identical for light bulbs, slightly different for "reactive" loads).

I can work out the theoretical maximum load (kettle on every socket), but that never ever happens. So what sort of figure are they looking for. Does it have to be accurate or will ball-park do?

One issue is that I am considering electrical storage heating, but might not. So should I just go with a three-phase connection and be done with it, or will that be stupidly expensive if not needed?

Thanks for your help!

G

 

[ericmark]

Most houses run on a 100A or smaller incoming fuse.
Kettle in every socket will not work as whole final ring likely to be protected by a 32 amp device.
I can not see why any house would need three phase.

but your question is like asking length of piece of string.

It does not matter how big the house is normally it will still have one washing machine etc.

Only electric heating is likely to take a house over the standard 60 to 100 amp supply.

It is all laid out in detail in the guide to 16th Edition and I expect same in guide to 17th Edition.

 

[Steve]

If its a new built house, future proof it.

Heating system - get an electric heat pump fitted. They are cheaper than storage heating, much more efficient. And require less maintenance than gas oil or coal. There are companies that specialise in these. But the good ones require a 3ph supply. These are more efficient.

On 3phase, you can have three electric showers without worrying about it, or a hot tub, kiln, particle accellerator etc.

 

[Galfredus]

It is all laid out in detail in the guide to 16th Edition and I expect same in guide to 17th Edition.

Thanks Eric. May I ask the 17th edition of what?

G

 

[Galfredus]

Heating system - get an electric heat pump fitted. They are cheaper than storage heating, much more efficient.

Thanks, yes I looked into heat pumps. Cheaper to run yes, even taking account of not using economy 7 overnight, but it seems A LOT more expensive to buy and install. It looks like all the grants available have not encouraged proper competition between makers. I understand they are much cheaper in Canada where they have been common for years.

I'm actually looking at a solid fuel stove, but it'll be a five bed house and I want back-up. I was toying with the idea of installing a GEC style Nightstor system on LPHW. My mum has one and it's been faultless for 20 years and very cheap to run. Otherwise it's oil or lpg.

 

[Steve]

Consider the cost to install gas central heating, the boiler, rads, pipework, controls, the gas supply itself, labour. It'll run into several thousand pounds.

For a GSHP, the initial outlay will save you money in the long term. Less servicing, no safety worries, and since this is a new build, it can be absorbed well into the overall budget.

Just a suggestion!



Though you may want a gas supply too for cooking.

 

[Taylortwocities]

Thanks Eric. May I ask the 17th edition of what?

G

BS7671

BS7671

• Taylortwocities
• 13 Feb 2009
• 1

 

[Galfredus]

Thanks Eric. May I ask the 17th edition of what?

G

BS7671

BS7671

• Taylortwocities
• 13 Feb 2009
• 1

Where do I get a copy? It doesn't look like the sort of thing the local library will be stocking....

 

[Taylortwocities]

Any electrical wholesaler,
also Amazon do it at a reasonable price.

I am a bit concerned that you are building a house (and doing the electrics?) yourself without even knowing about Wiring Regulations.

If DIY is your plan then I suggest you forget that for the electrics and find a registered electrician who will do the work - and help you deal with the Frenchie Poos.

 

[flameport]

For the original question, a 100A single phase supply should be suitable - even with electric heating. As this is a new build, it will have huge amounts of loft, wall and floor insulation, so the heating requirements will be much less than for an older property.

You presumably won't be installing any electric showers - there is no reason at all to fit these in a new property.

If they are asking for a kva figure, 15 or 17 is probably what you want.

 

[Galfredus]

Any electrical wholesaler,
also Amazon do it at a reasonable price.

I am a bit concerned that you are building a house (and doing the electrics?) yourself without even knowing about Wiring Regulations.

Don't worry - I have no intention of doing any wiring at all. But I do need to get the electrical supply lined up in advance - hence my need to have an idea of what my useage might be.

 

[Galfredus]

If they are asking for a kva figure, 15 or 17 is probably what you want.

I hope to avoid electric showers. The only other non-obvious appliance I can foresee using is an arc welder, but only one that will go in a normal 13 amp socket.

You are right about the insulation, but the problem with a storage heater (if I go down that road) is that it charges at full belt regardless of how much insulation I have, so peak useage will be the same regardless. Though I doubt I'll be welding in the middle of the night....

I'll also have an electric oven, but not electric hob, I'll use calor for that (no mains).

so 15-17 still sounds about right?

 

[flameport]

Storage heaters can be adjusted to vary the input power, the idea being that the heaters are adjusted in the evening depending on how cold it will be on the following day.

A properly insulated building will need smaller heaters which will use less power than larger ones.

Storage heaters should be avoided though, as they are a poor solution compared to most other types of heating.

 

[ericmark]

The 17th edition is published by the IET and BSI but I did not say 17th Edition but On-Site Guide (BS 7671:2008 Wiring Regulations, 17th Edition) which is a lot cheaper £20 and a lot more helpful for what you want. The guide is also published by the Union Unite THE ELECTRICIANS GUIDE TO GOOD ELECTRICAL PRACTICE which is cheaper.

I do wonder why people go to book shops to buy these I have always gone direct which is cheapest option if your a member.

There are of course many other guides the Electrical Safety Council do Best Practice Guides and there is also the Wiki section on this.

But if you say why you have considered 3 phase then maybe we can give a more informed answer.

 

[Galfredus]

Storage heaters should be avoided though, as they are a poor solution compared to most other types of heating.

Yes, I hope logs will do most of my heating! The only other options for me are oil or LPG, both of which need tanks in the (very small) garden.

I'm not talking about separate storage heaters, but a single unit heating a LPHW system via a heat exchanger. The only reason I need backup is because there will be periods when I'm not around. Having a fixed rate on economy 7 gives a certain peace of mind over a tank that will probably need filling at exactly the wrong time (price wise).

If I'm talking rubbish please do let me know!

G