How much kVA do I need?

[sam851]

I'm hoping somebody can help me.

Im converting a 4bedroom flat to 3 x 1bedroom flats.

I am having a new 3 phase supply installed for 3 the flats. UK Power Networks have asked me how much kVA will I be needing in total.

Each flat will have its own gas supply with the heating & hot water supplied from the boiler. The cookers will be all/mostly gas.

I understand the capacity for a 3 phase is about 70kVA, however the DNO has said that there is limited amount of space available on the network and if the full 70kVA is required they may need to pass my application to another department to price and install, which is considerably more expensive.

My question is how much kVA would I actually need for the 3 1 bedrooms flats?

 

[bill01803]

Speak to your designer/electrician

 

[brianmoooore]

A 'standard' supply for a large house in the UK is 15kVA, which should give you some idea.

 

[Rockingit]

TBH, you almost certainly don't need to convert the incomer anyway. You've no electric heating, no power showers (I assume) so the only thing that's left are some small white goods, lighting and I.T. None of which will touch a 100A / 15kVA main service. What you may need to install is a NBO system - find a decent electrician.

 

[catdog1121]

A three phase supply would be fine, even if all phases were only 60A, although more likely 100A.. Maybe go bigger though to give room for EV charging and heat pumps in the future?

 

[sam851]

TBH, you almost certainly don't need to convert the incomer anyway. You've no electric heating, no power showers (I assume) so the only thing that's left are some small white goods, lighting and I.T. None of which will touch a 100A / 15kVA main service. What you may need to install is a NBO system - find a decent electrician.

The existing electricity supply for the flat is currently coming from the ground floor shop which has a 3 phase supply head.

The flats (on first and second floor) will have their own communal entrance which will be completely independent of the ground floor shop. Which is why I want to install a new 3 phase supply for the flats in the communal entrance. I want the flats to have their own meters where they are billed directly by the energy supplier.

 

[sam851]

A three phase supply would be fine, even if all phases were only 60A, although more likely 100A.. Maybe go bigger though to give room for EV charging and heat pumps in the future?

So what kVA figure should I give to UKPN?

 

[Petej999]

I'm hoping somebody can help me.

Im converting a 4bedroom flat to 3 x 1bedroom flats.

I am having a new 3 phase supply installed for 3 the flats. UK Power Networks have asked me how much kVA will I be needing in total.

Each flat will have its own gas supply with the heating & hot water supplied from the boiler. The cookers will be all/mostly gas.

I understand the capacity for a 3 phase is about 70kVA, however the DNO has said that there is limited amount of space available on the network and if the full 70kVA is required they may need to pass my application to another department to price and install, which isHow long is a piece of string? considerably more expensive.

My question is how much kVA would I actually need for the 3 1 bedrooms flats? how long is a piece of string?

 

[Rockingit]

So what kVA figure should I give to UKPN?

10kVA per dwelling.

 

[pc1966]

So what kVA figure should I give to UKPN?

3 * 60A is just over 41kVA and for a flat should be fine unless they are apt to use a high power shower while running a big cooker!

 

[Rockingit]

3 * 60A is just over 41kVA and for a flat should be fine unless they are apt to use a high power shower while running a big cooker!

Neither of which appear here. As I first said, if ever there was an example of overthinking something..... 100A incomer, 3 red links, 3 meters, 3 KMF's @60A and walk away....

 

[pc1966]

Neither of which appear here. As I first said, if ever there was an example of overthinking something..... 100A incomer, 3 red links, 3 meters, 3 KMF's @60A and walk away....

I think the OP is being asked by the DNO for a new supply! I suspect to detach the billing from converted flats from the shop's supply.

I agree with you, 60A per flat is fine and the existing shop supply is probably fine to have them fed via meters and fused-switches.

 

[Rockingit]

I think the OP is being asked by the DNO for a new supply! I suspect to detach the billing from converted flats from the shop's supply.

I agree with you, 60A per flat is fine and the existing shop supply is probably fine to have them fed via meters and fused-switches.

Doubtless to make a sale and that reason only.... Multiple MPans can be sourced from the same supply

 

[pc1966]

10kVA per dwelling.

Would they do a 40A supply, or are they going to do 60A and trust you don't abuse it?

I think in France they are quite assertive about limiting your power to what tariff you pay for, but never had to discuss that policy here.

 

[Rockingit]

Would they do a 40A supply, or are they going to do 60A and trust you don't abuse it?

I think in France they are quite assertive about limiting your power to what tariff you pay for, but never had to discuss that policy here.

More a case of just being realistic to avoid an overcharge, I can't see them actually putting in under 80A to be fair. But operating at 60A just makes everything so much easier - 16mm tails etc etc

 

[pc1966]

More a case of just being realistic to avoid an overcharge, I can't see them actually putting in under 80A to be fair. But operating at 60A just makes everything so much easier - 16mm tails etc etc

True, also you would get selectivity between a 100A DNO fuse and your 60A local one.

 

[sam851]

Thanks for replies. So i'm looking at saying somewhere 30-40kva to the UKPN.

Its actually my idea for the new 3 phase supply to the flats. I just want the ground floor shop and the flats to be as independent as possible to minimise future management of tenants of the shops and the flats.

Also would about a 3-4kva allowance be a reasonable amount for the communal entrance for the flats? There would be lighting (internal and external), a Grade A fire alarm system with control panel, some emergency lighting and a single socket.

The idea would be to fit a 4 way Ryefield board over the new 3 phase supply head so that I can split the power and connect 4 meters. From what I've found out this is he most correct way to do the split.

I may sell the units individually in the future, so I just want the flats to be correctly split.

 

[timhoward]

Just a comment that the form is horrendous and I have to think carefully and hard filling it out - get a sparks to look over the form before you hit send!

 

[Rockingit]

Thanks for replies. So i'm looking at saying somewhere 30-40kva to the UKPN.

Its actually my idea for the new 3 phase supply to the flats. I just want the ground floor shop and the flats to be as independent as possible to minimise future management of tenants of the shops and the flats.

Also would about a 3-4kva allowance be a reasonable amount for the communal entrance for the flats? There would be lighting (internal and external), a Grade A fire alarm system with control panel, some emergency lighting and a single socket.

The idea would be to fit a 4 way Ryefield board over the new 3 phase supply head so that I can split the power and connect 4 meters. From what I've found out this is he most correct way to do the split.

I may sell the units individually in the future, so I just want the flats to be correctly split.

You DEFINITELY need an experienced contractor to look after this for you, this is significantly beyond DIY research.

 

[sam851]

The work will definitely be done by a qualified electrician. But as I am in the planning stages I just want to get my head around how the major parts works. The entire conversion will be given to a building contractor to do, who will probably sub contract out the electrical work. I will be responsible for getting the new supply installed to save on costs, so as of now I don't have an electrician yet who I can call to get the answers.

The plan is to tell UKPN I need 40kVA on the new 3 phase supply. They install the new 3 phase supply with the cut out head. The fuses will either be 3 x 60A , 3 x 80A or 3 x 100A depending what UKPN decide to install. The electrician would then install a 3 phase 4 way Ryefield board straight above the cut out head. This will feed into the 4 meters, with an Isolator switch after each meter. The communal consumer unit will be in the same location. The consumer units for the flats will be inside each flat.

Can the cable thickness of the incoming 3 phase supply vary ? or is it a standard thickness?

Am I missing something in the above set up?