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

 

[Pete999]

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

Is the house going to be a Family home, with 9 of the bedrooms turned into a sort of "Bed Sit" scenario, will it become a HMO? if all of the rooms will have the same electrical installation then assess 1 and times it by 9.
However will the rooms be metered separately? how will or do you intend to supply the rooms with electricity? lots more things need to be considered, is there a design to work to? or is this a suck it and see type of thing. Best give your design to a decent contracting firm and let them sort out the supply size, although this will need careful consideration, by yourself and the contractor.

 

[plugsandsparks]

Best way is to find out what you have now and what loads you will have in the future.
ASHP KW input will be needed, kitchen appliances KW needed for each unit. The rooms dont sound particularly thirsty, does the ASHP and MHVR exist now ?

 

[Pemhughes]

Cheers for the replies so far.

It will be an HMO with all bills included, so no individual meters needed, thankfully. We will have a single smart meter and consumer unit, with each bedroom on their own loop. We also have a UPS for the LED lighting to the halls and stairs to the final fire escapes.

I have electrical plans drawn with regard to the amount and locations, so could create a table of total demand, as suggested.

Speaking to a friendly spark, he mentioned allowing roughly 2500kWh per bedroom having reviewed a floorplan pic, considering we have LED lighting and only a few sockets in each - hard to gauge, does that sound about right?

At this time as we need to work it out for the tender, I was considering appointing and paying an electrician direct to de-risk the connection size required; however, I thought I would tap into this considerable knowledge pool first!

 

[plugsandsparks]

Not from what you have listed, need a list of loads for whole property

 

[Wilko]

Hi - apologies if I have missed it, but can you advise what the existing supply capacity is please?

 

[Pemhughes]

Hi - apologies if I have missed it, but can you advise what the existing supply capacity is please?

Hi Wilko, unknown I will check the client information and see what we can find.
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Not from what you have listed, need a list of loads for whole property

I thought this may be the case, compiling what I can now.

 

[davesparks]

We also have a UPS for the LED lighting to the halls and stairs to the final fire escapes.

I have electrical plans drawn with regard to the amount and locations, so could create a table of total demand, as suggested.

Speaking to a friendly spark, he mentioned allowing roughly 2500kWh per bedroom having reviewed a floorplan pic, considering we have LED lighting and only a few sockets in each - hard to gauge, does that sound about right?

Why a UPS to supply the lighting? Unless this is designed as an emergency lighting system and compliant with the relevant BS located correctly, with fire proof cabling etc etc then it won't satisfy your emergency lighting requirements.

Can the electrical designer who drew the plans not provide the calculations too?

2.5kW (I assume you didn't mean kWh as that makes no sense) sounds like a lot of power for a bedroom to me, but I haven't seen the plans.

Your best bet would be to get the full electrical design carried out as a seperate job to the actual installation.

 

[Pemhughes]

Morning All,

To answer a few queries:

1. We drafted the electrical layouts (architect), it sounds as though appointing an electrician to undertake is the safest bet.
2. After a 1-hour on hold phone call with EON, we are told the existing supply is 3.372kWh;
3. UPS is required for emergency lighting only (HMO regulations)

Attempting putting the list of products together is like reading a foreign language with different figures electrical figures and values.

 

[Simon47]

2 makes no sense
3 is just wrong
Requirement for emergency lighting is for it to be independent of an external power supply - how that is arranged is a matter for the designer and the client between them to work out the requirements and trade offs. It can be a central battery system (almost certainly not a UPS), but as advised, that means all fire rated cabling and other stuff. Or it can be with self contained emergency light luminaires (ie local batteries) - in which case no special cabling is required. Or in some situations (I doubt yours is one of them) there are luminous (glow in the dark) sticker based systems*.
It really is a bit of "6 of one, half a dozen of the other" as both options have downsides. Regardless of which way you go, there will need to be an inspection, maintenance, and test regime in place - along with other stuff like the fire alarm.

* I have seen these in a few situations. Most notably on board ships where they typically have corridor lights on permanently and so the luminous material can be constantly "charged". These situations tend to have a requirement for continuous low-level (as in, near the floor) illumination, often with directional arrows to guide people to the exits.

 

[Pemhughes]

2 makes no sense
3 is just wrong
Requirement for emergency lighting is for it to be independent of an external power supply - how that is arranged is a matter for the designer and the client between them to work out the requirements and trade offs. It can be a central battery system (almost certainly not a UPS), but as advised, that means all fire rated cabling and other stuff. Or it can be with self contained emergency light luminaires (ie local batteries) - in which case no special cabling is required. Or in some situations (I doubt yours is one of them) there are luminous (glow in the dark) sticker based systems*.
It really is a bit of "6 of one, half a dozen of the other" as both options have downsides. Regardless of which way you go, there will need to be an inspection, maintenance, and test regime in place - along with other stuff like the fire alarm.

* I have seen these in a few situations. Most notably on board ships where they typically have corridor lights on permanently and so the luminous material can be constantly "charged". These situations tend to have a requirement for continuous low-level (as in, near the floor) illumination, often with directional arrows to guide people to the exits.

Thank you, Simon.

The UPS was requested by an attending HMO officer, which appears very much incorrect.

This, coupled with the wrong advice from Eon make it clear this is not an area I'm going to design or specify.

We will appoint a local electrician to undertake the work correctly and create the calculations for us.

Thank you all for your assistance.

Best Regards,
Pete

 

[Simon47]

Feel free to come back with an update on how you get on, or if you want any proposals "sanity checking".

 

[Pemhughes]

Simon, that would be excellent, thank you.

We have appointed a spark to undertake the calculations and design - he echoed the UPS statement.

Thank you for your input, exactly what we needed.

Best Regards,
Pete

 

[shaun1]

At this scale you may almost be requirng the services of an electrical design engineer, rather than just a local electrician. I would imadgine there are many electricans out there that are capable of designing this instalation, but there are also many out there that aren't, and some that think they fall in to the former catagory when they definitely fall in to the latter.

But there are pleanty of people on here that would advise further if you get something drawn up.

 

[Pemhughes]

Evening All,

We have received the calculated loads for the 9 bed HMO, which were advised as 68kW, 86kVA.

The utility provider has returned comments stating this is unusually high, giving the table attached as previous examples.

I wonder whether the issue is with the specification of each bedroom as having a 4.4 kW allowance, which may align more to a standard 1 bed flat, than an HMO bedroom?

Thoughts 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!
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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