Upgraded supply needed?

[Pemhughes]

Good Afternoon All,

I hope I have posted this in the right sub-forum.

In short, what would be the best way to work out if we need an upgraded KvA supply if we are creating a 9-bedroom shared home in an existing five-storey residential dwelling?

Each bedroom has a small snack station (with a small fridge only), en-suite (plumbed, NOT power-shower, but does have a shaver socket) and desk with 3 x USB double sockets per bedroom and a smart-TV wall mounted. They are kitted out like 1-bed apartments without the kitchen.

We also have a large shared kitchen/living/dining with 2 double ovens, 2 x gas hobs, 2 x washer/dryers, 2 x microwaves with 4 sockets for additional coffee makers, bread makers, slow cookers, etc as well as 2 TVs.

Plant wise, we have an MVHR unit and an air-source heat pump with backup immersion heater, just in case.

Typically we would ask the appointed spark for a calculation; however, we are out to tender for the contractors so do not have anyone appointed yet and we would like to book in the upgraded supply now if needed.

Any thoughts and advice most welcome.

Best Regards,
Pete

 

[Simon47]

Agreed - 4.4kW/room is nuts, assuming no electric heating. Looking back at your OP, it sounds like each room only needs a few hundred W.
I'm assuming the ASHP is providing heating ?

 

[Pemhughes]

Thank you Simon,

I am now a bit stuck, the electrical designer has noted c. 3kW per bedroom, reducing the overall load to 51kW c. 64kVA. for all 9 bedrooms plus common areas.
The supplier has noted this would typically power 45-50 standard homes (there are 3 x 9 bed HMOs)


Every HMO bedroom has the same electrical load/requirements, see the below typical layout.

The electrical requirements are:

• Small fridge-freezer - https://business.currys.co.uk/catalogue/item/B128685B
• Smart TV;
• c. 7 sockets for laptop/PC, hoover, fans, perhaps a toaster, etc;
• Shaver socket to the en-suite
• c. 2-3 LEDs to the bathroom
• c. 6-8 LED lights, per bedroom;

There are no other electrical provisions, no electrical radiators (all heating and hot water are via the ASHP, including the shower), no kitchens, etc.

Strikes me as still over provided, but then I am by far away not an expert.

What do you think would be a reasonable provision per bedroom for the above and below, with tolerance?

 

[davesparks]

3kW per room seems OK to my mind, possibly a little on the high side but not drastically.
However you can't just take 3kW and multiply it by 9 for 9 rooms, you need to apply diversity to this figure.
The electricity suppliers use diversity factors to arrive at the admd (after diversity maximum demand) figures in the table you posted earlier.

It's important to note that the admd is not the maximum capacity of the supply, it is more of an average considered over a large number of supplies.

 

[Simon47]

Small fridge-freezer - https://business.currys.co.uk/catalogue/item/B128685B

https://business.currys.co.uk/catalogue/item/B128685B
Average probably under 100W

Smart TV;

Allow up to 300W

c. 7 sockets for laptop/PC, hoover, fans, perhaps a toaster, etc;

Excluding the toaster, say 500W max

Shaver socket to the en-suite

Not worth counting

c. 2-3 LEDs to the bathroom
c. 6-8 LED lights, per bedroom;

If all on, maybe 100W - and the occupant will need dark glasses

So without considering diversity, that's around 1kW per room - say 2kW with the toaster. As Davesparks says, you then need to apply some diversity - will everyone fire up a hoover at the same time, will everyone have a toaster and fire them up at the same time ? Even if everyone has toast for breakfast, each toaster will only be running for a few minutes and unlikely to be at the same time.
TBH I have no idea how you'd work out the diversity for that sort of property, but in my mind I reckon you'd struggle to sustain over 10kW between the 9 rooms. Might peak over that for short periods (minutes), but definitely not sustain it.

 

[Pemhughes]

https://business.currys.co.uk/catalogue/item/B128685B
Average probably under 100W

Allow up to 300W

Excluding the toaster, say 500W max

Not worth counting

If all on, maybe 100W - and the occupant will need dark glasses

So without considering diversity, that's around 1kW per room - say 2kW with the toaster. As Davesparks says, you then need to apply some diversity - will everyone fire up a hoover at the same time, will everyone have a toaster and fire them up at the same time ? Even if everyone has toast for breakfast, each toaster will only be running for a few minutes and unlikely to be at the same time.
TBH I have no idea how you'd work out the diversity for that sort of property, but in my mind I reckon you'd struggle to sustain over 10kW between the 9 rooms. Might peak over that for short periods (minutes), but definitely not sustain it.

Excellent, thank you, Simon!
[automerge]1577997860[/automerge]

3kW per room seems OK to my mind, possibly a little on the high side but not drastically.
However you can't just take 3kW and multiply it by 9 for 9 rooms, you need to apply diversity to this figure.
The electricity suppliers use diversity factors to arrive at the admd (after diversity maximum demand) figures in the table you posted earlier.

It's important to note that the admd is not the maximum capacity of the supply, it is more of an average considered over a large number of supplies.

And thank you, too, Dave

 

[telectrix]

yeah 2kW /room is more than adequate for load calculations.