Service Position Relocation

[silentboarder69]

Hi,
we've contacted the leccy regards relocating the service position. They've sent a form back, and I'm stuck on one question.
They've asked how many kVA I require. The service supplies three/four flats, so I replied 110 kVA and single phase supply. They replied saying the max you could have is 72 kVA, and confirm that I want a three phase supply.
So, I just wanted to confirm is I wanted a three phase supply! Would this be the norm for three/four flats? All two beds, maybe one three bed, central London.

Thanks in advance for your help!

 

[topquark]

That's way OTT, what have you calculated the load for each flat and common areas (lifts maybe requiring three phase) as?

 

[silentboarder69]

100A per flat? No lifts.
Maybe I used their formula incorrectly, I don't have it to hand, it's on another computer.

 

[topquark]

100A per flat? No lifts.
Maybe I used their formula incorrectly, I don't have it to hand, it's on another computer.

Are these two bed flats, even 100A per flat sounds a lot. I would have guessed that you'd be well within 60A per flat, but I would be guessing.

 

[topquark]

If it's really 100A per flat and there's four flats then the supply would be: 400A x 230V / 1000 = 92kVA

They'd have to be pretty big flats to warrant that sort of a supply though.

I would think that 240A x 230V / 1000 = 55.2kVA would be adequate, but without knowing the total demand per flat I couldn't say with any degree of confidence attached to it.

 

[silentboarder69]

Thanks, and if we opted for the 72kVA, we'd have a three phase supply right?

 

[topquark]

Thanks, and if we opted for the 72kVA, we'd have a three phase supply right?

The capacity requested is normally per phase, check the forms. You should confirm with your supplier.

 

[silentboarder69]

The formula supplied by the elec company is 4A=1kW 1kW=1.1kVA
So if each of the flats is 60A, means 60kW, which is 66kVA (if I'd been looking for 100A, 110kVA).

So, I need 66kVA. The next question is single or three phase. Each flat will only require single phase, but is a three phase supply needed for the building to supply the three flats?

 

[topquark]

Are you getting one supply in and having landlord meters for each flat or are you asking the DNO to supply a separate meter per flat? The latter would probably be prohibitively expensive I suspect.

Not sure I understand their maths, but if that's what they say to use (it's for their capacity planning). So by your reckoning 66kVA per flat.

If you've only three flats (not four) then three phase may be ok as you've probably got little common area to cater for, so one phase per flat would do. BTW You used to have to label locations where it was possible to touch across phases, but that may have changed recently I recall, you'll need to check the regs.

Give some thought to available space where the supply is coming in, do you have room for the equipment for the method of supply your considering asking for. Also cable routes to the flats (and type of cable).

 

[silentboarder69]

DNO?

Each flat has a meter already, which don't necessarily need replacing. The existing cable for each flat is protected by a 60A fuse. Essentially, the service cable comes into the clients flat, and there are four 60A fuses. Then one meter (for my client's flat), and three cables running up through the building to each individual's flat, where presumeably they have a meter. There are no meters in the communal areas.

I think 60x4=240A
4A=1kW
240/4=60kW
1kW=1.1kVA
60x1.1=66kVA

So, 66kVA for the building?

 

[topquark]

DNO?

Each flat has a meter already, which don't necessarily need replacing. The existing cable for each flat is protected by a 60A fuse. Essentially, the service cable comes into the clients flat, and there are four 60A fuses. Then one meter (for my client's flat), and three cables running up through the building to each individual's flat, where presumeably they have a meter. There are no meters in the communal areas.

I think 60x4=240A
4A=1kW
240/4=60kW
1kW=1.1kVA
60x1.1=66kVA

So, 66kVA for the building?

DNO = distribution network operator.

For the building is more like it, I thought from the figures you presented you were suggesting that per flat

So are there 3 flats or 4?

 

[silentboarder69]

OK, I think I just understood what you meant when you said they normally state how much you need per phase, and the 72kVA.
So, I've requested 4x100A, which was 110kVA, and a single phase supply.
The leccy guys have said 'It's a max of 72kVA. I presume you need three phase'.
Which would be true, as you'd have three phase with 36kVA per phase, up to a maximum of 72kVA per phase.
If I stick with 66kVA, I only require the single phase supply, as long as each flat sticks to 60A, which shouldn't be a problem as they're not big flats.
So, I should request 66kVA and single phase supply, no new meters as everything existing can be kept.

Does that make sense?!

 

[silentboarder69]

Four flats, but I'm only working in one, but the services enter this flat, and the wall to which it is mounted is falling down and requires a rebuild. Hence taking the opportunity to relocate it in a position accesable by all properties.