kva for a flat with all electric heating

[Gus Beare]

Hi everyone

I am tearing my hair out here. I have trying to get UK Power Networks to quote for new electrical supplies in a property development I am managing. The property is a conversion into four one bed flats.

I have been asked by UKPN to provide the After Diversity Max Demand in kVA for each unit. I have asked an electrician and he said 20kVA. I asked another and he said 24 kVA.

But UKPN said this:

"UK Power Networks would in general expect the (ADMD - after diversity maximum demand) for a gas heated flat/house to be between 1.5kVA and 3.0kVA and an electric heated flat/house to be between 5kVA & 10kVA unless abnormal high usage appliances are being installed."

These units will have electric wall heaters and will be very well insulated.
They will also each have 125l unvented cylinders for water heating. They will each have an oven/grill and washing machine.

I have asked UKPN how they arrived at this figure and they pointed me to their web site (which only confuses matters and fails to show how this is calculated):

UK Power Networks - What are Watts (W), Kilowatts (kW) and Kilovolt Amps (kVA)? - https://www.ukpowernetworks.co.uk/internet/en/help-and-advice/need-help/what-are-watts.html

But on their site it says this:

" If you’re unsure and don’t tell us what you need then we would assume 15kVA but it’s important you get this right. "

I cannot seem to get them to explain. Either they are clueless or I am clueless or both.

Can anyone help?

thanks
Gus

 

[DPG]

How is the supply split to each flat? What fuses are feeding them?

 

[Strima]

As has been stated before you will not have all appliances running at full load at the same time.

Once the heaters and oven are up to temperature they start cycling and the load drops right off.

Sockets and lighting I would expect to see no mare than 9 amps for an average 4 bed house. Yes this will spike when the kettle goes on etc but this is for a very short duration.

On a rough calculation you could more than likely get away with a 15kVA per flat.

However what sort of client are you aiming for? Young single professionals would have different usage and timings than a family with four kids...

 

[Gus Beare]

Thanks Strima, that's very helpful. As UKPN networks stated they suggest 5-10vVA ADMD for an electrically heated home. However, they are unable to tell me how they arrived at this estimation.

The four flats will be almost certainly be rented to young professionals. They will be out all day during the week but will likely have very similar energy usage patterns. i.e. They will want the heating on for a spell in the morning and evening. They will all be home around the same time and likely to put the oven on.

During the summer this will not be an issue at all. I just want to be covered for hard, cold spells during the winter.

However, I am coming around to the idea that 17.25kVA should be enough per flat. I just want to make sure I make the right decision now as getting it wrong now could be a nightmare later.

 

[Gus Beare]

UKPN came back to me and said they could supply 23kVA by routing from another source without additional cost so am going with that.
I got a quote from them and ma now looking to find someone to do the contestable stuff. UKPN are very slow and the quote seems a lot.

Can anyone recommend a contractor that can do this kind of stuff in South London?
thanks

 

[Peter1981]

I'm in exactly the same situation as you and the same area.

Did you manage to find someone to do your contestable work?
How long did UK power networks take to carry out their work?

Many thanks

Pete

 

[Thirst]

UKPN came back to me and said they could supply 23kVA by routing from another source without additional cost so am going with that.
I got a quote from them and ma now looking to find someone to do the contestable stuff. UKPN are very slow and the quote seems a lot.

Can anyone recommend a contractor that can do this kind of stuff in South London?
thanks

Hi Gus,

This thread has been very interesting. I am in a similar situation. I have a large house that is being converted to 4 x 1 bed flats for young professionals plus a landlord supply. That means 4 x dishwasher, washer/dryer, induction hob, electric oven etc. I also want the landlord supply to be enough to allow for an electric car charge point in the future. I also want to plan for the fact it's looking like gas boilers will be phased out in favor of electric within 10-15 years.

My spark came back and said each flat would have an 80Amp (AD) demand based on appliances and that 100Amp would be ideal given lighting, plugs etc So 23Kva.

5 x 23Kva = 115KVa

My next question is that Ryefield boards are designed to sit on a 100Amp supply (at least the ones I've looked at). A 115KVa supply would exceed this, no?

UK Power really need to do a dummys guide 101 on this.

Asking as a property owner/non-spark.

 

[davesparks]

Hi Gus,

This thread has been very interesting. I am in a similar situation. I have a large house that is being converted to 4 x 1 bed flats for young professionals plus a landlord supply. That means 4 x dishwasher, washer/dryer, induction hob, electric oven etc. I also want the landlord supply to be enough to allow for an electric car charge point in the future. I also want to plan for the fact it's looking like gas boilers will be phased out in favor of electric within 10-15 years.

My spark came back and said each flat would have an 80Amp (AD) demand based on appliances and that 100Amp would be ideal given lighting, plugs etc So 23Kva.

5 x 23Kva = 115KVa

My next question is that Ryefield boards are designed to sit on a 100Amp supply (at least the ones I've looked at). A 115KVa supply would exceed this, no?

UK Power really need to do a dummys guide 101 on this.

Asking as a property owner/non-spark.

Off the top of my head that seems like a very high demand for each flat.

Ryfield boards are normally designed to be supplied at a bit more than 100A, they usually have 100A rated outgoing ways.

Nobody is going to produce a dummies guide because it is a technical subject and involves well established scientific principles and calculations, without learning this and gaining experience working alongside those who are experienced at it you can't get it right.
There are too many variables and considerations to reduce it down to a simplified guide.

 

[peterinreading]

I have done several similar installations in an SSE area. In two cases I estimated that a 60 Amp supply would be adequate for each flat but SSE insisted on providing 100 Amp supplies.