Converting residential home to flats - newbie

[paulgranger]

Hi All,

Any advice on my newbie question is appreciated. I'm looking to convert a disused residential home to 12 bedsit type rooms. Each will have an electric shower, electric oven/hob, small fridge plus the usual electrical appliances. There is also a communal area with washers and driers as well as communal corridors and areas with lighting, heating, electric access doors etc.

The building already is split into two halves each with a 3 phase supply, both from 1 meter. Looking in the meter cupboard it looks like 3 x 100 amps so a 300 amp supply?

I'm just in the development/budgeting phase of this project and trying to scope what i need. I have little knowledge around electrics and appreciate I'll need to get in some expert help but wanted to gather some info first. I'm aware than getting the supply to the property increased may well be quite costly and might make the project non-viable.

How do I work out how much electricity supply im likely to need for the building once converted. Do i go room by room and add up the likely amps in total for each room (allowing for the fact that not all appliances will be used at once). Would it be correct to look at this in amps?
Does the existing 3 phase supply make any real difference to this?
I'm assuming i'll need to speak to uk power networks for a quote to increase supply but how much would i tell them i'd need? Should I get a sparky in to go through it with me at this stage or is it something i can do a rough calculation for myself? Couldn't find the info i was looking for online.

Currently the plan is for one supply paid for by the landlord with the tenants paying all inclusive of bills in their rent. Consideration is being given to individually metering the rooms/flats.

If/when i do speak with uk power networks are there any tips on how to deal with them or any things to look out for.

Thanks in advance
Paul

 

[davesparks]

The best thing to do is have a gas boiler to heat hot water storage tank(s)

You are right that a 100A 3 phase supply is effectively the same as 3x 100A single phase supplies (for the purposes of a domestic installation) so you have theoretically got 300A available, UKPN will describe this as a 70KVA supply.

Have you got planning permission for this project yet?

 

[paulgranger]

Thanks for the response davesparks

Yes planning permission has been granted and now working through the building regs and how best to work the utilities. I just couldn't quite fathom whether i have enough supply already to do what i want. Whether i need to get an increased supply from UKPN or on balance of cost:benefit change my plans.

I was thinking about keeping the existing gas boiler system from the existing Residential/Nursing Home and supply the water to the taps and central heating to each flat in this way. Were you suggesting it'd be best to use this for the showers rather than electric showers?

Inside the building are 2 fuse boxes, one at each end of the building, both stating they are 3 phase.
In the meter cupboard outside there are 3x fuses(?) each stating 100Amps. Does this mean i have 3x100amp meaning 300amp supply or 3 x100amp x 3 phase meaning 900amp supply?

Excuse my ignorance just trying to get the correct next steps in place. I had some conflicting information from a 'handyman' about what i have/need and i know hes not an expert. I didnt want to approach UKPN without more info as I assume they'd turn me back.
Perhaps need to just get a good electrician to come have a look and chat me through it?

Thanks again
Paul

The best thing to do is have a gas boiler to heat hot water storage tank(s)

You are right that a 100A 3 phase supply is effectively the same as 3x 100A single phase supplies (for the purposes of a domestic installation) so you have theoretically got 300A available, UKPN will describe this as a 70KVA supply.

Have you got planning permission for this project yet?

 

[NDG Elecs]

As DS says, gas and water tanks for the showers would massively cut the overall demand which may in turn make the existing supply sufficient. Upgrading the supply will have three zeroes at the end of whatever price they decided to pluck out of the air! Whatever you decide it will cost an arm and a leg to do the wiring. Having the electricity bills included in the rent will make it cheaper from your perspective as twelve individual meters, sub mains and CUs would cost a lot more. But saying that you still need to ensure an individual bedsit is not completely plunged into darkness in the event of nuisance tripping occurring.

To be honest I would struggle in designing the installation adequately, and I would suggest getting an electrician that has previous experience of this.

You will also need a proper fire alarm system throughout the property. And emergency lighting too. Building Control will likely be very stringent on the requirements, and rightly so, given the nature of the accommodation. Get them onside early on, and ask for them to put in writing what they expect as a minimum.

3x100 amp =300. The three phases are 100amp each.


Good luck, you might need it!

 

[paulgranger]

Thanks for the quick reply. Really helpful!

It looks like what you say is the way to go although I do wonder if the existing supply will be enough even if no electric showers as each flat will have its own elfin kitchen.
Should I just add up the amps for each thing including the communal/security stuff and make sure its not too far over 300amps? (think i'll get a reputable sparky into this)

Some work has already gone on re security, fire and lighting ideas but going to wrap it all up with one electrician if I can.
Building regs have been good so far as the architect has a good relationship with them previously.

Cheers for the advice
P

ps- any suggestions for an electrician covering the peterborough area would be most welcome! :smile5:

As DS says, gas and water tanks for the showers would massively cut the overall demand which may in turn make the existing supply sufficient. Upgrading the supply will have three zeroes at the end of whatever price they decided to pluck out of the air! Whatever you decide it will cost an arm and a leg to do the wiring. Having the electricity bills included in the rent will make it cheaper from your perspective as twelve individual meters, sub mains and CUs would cost a lot more. But saying that you still need to ensure an individual bedsit is not completely plunged into darkness in the event of nuisance tripping occurring.

To be honest I would struggle in designing the installation adequately, and I would suggest getting an electrician that has previous experience of this.

You will also need a proper fire alarm system throughout the property. And emergency lighting too. Building Control will likely be very stringent on the requirements, and rightly so, given the nature of the accommodation. Get them onside early on, and ask for them to put in writing what they expect as a minimum.

3x100 amp =300. The three phases are 100amp each.


Good luck, you might need it!

 

[davesparks]

There are various calculations that can be done to assess the maximum demand of an installation.
Ideally you will need the power ratings of the cooking appliances for this. If you don't have the details then as a rule of thumb a single oven is ~2.4KW and a 4 ring hob ~7KW

 

[paulgranger]

There are various calculations that can be done to assess the maximum demand of an installation.
Ideally you will need the power ratings of the cooking appliances for this. If you don't have the details then as a rule of thumb a single oven is ~2.4KW and a 4 ring hob ~7KW

Cheers for this. The language you've used has helped me google some resources to look at. I clearly wasnt in the know with which search terms to use!

thanks
paul

 

[davesparks]

Cheers for this. The language you've used has helped me google some resources to look at. I clearly wasnt in the know with which search terms to use!

thanks
paul

Just remember that you can't really trust the random crap you find online, there's a hell of a lot of wrong information out there!
You really need to employ someone who knows what they are doing to design the installation

 

[Andy78]

Just remember that you can't really trust the random crap you find online, there's a hell of a lot of wrong information out there!
You really need to employ someone who knows what they are doing to design the installation

This is the best advice you are likely to get given the myriad factors involve with this project.
A maximum demand needs to be calculated and assessed by a professional electrician with previous experience of project design in the first instance.
The design of the flats, their appliances, and their methods of heating will be critical to this, so the flat design needs to be thought out between you first.
With the demand you can then assess the adequacy of the supply and any supply upgrades needed. If upgrades are needed then they need to be quoted for and weighed up against other options for viability.
The design and planning of the electrical installation of the flats can then be finalised and the project can progress.