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# Help regarding three-phase upgrade for flat conversion

Discuss Help regarding three-phase upgrade for flat conversion in the Commercial Electrical Advice area at ElectriciansForums.net

#### Vedb

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Hello all,

I am about to receive planning permission for 6 one bed flats conversion from an existing family home. The current single phase 100A supply will not be sufficient so I have applied for a 3-phase upgrade.

My question is on maximum electrical load per flat.

I have done a similar project in the past where the 69kVA was sufficient for 6 flats. This house is double the size however the electrical demand is the same. SP Networks are asking what the load would be per flat (all identical) and how much I would like for the LL supply.

Am I wrong to assume 11.5kVA is enough for each one bedroom flat?

The landlord supply will have just four or five lights and some sockets. The flats will all be electrically heated with 2 x 2kW panel heaters, electric towel rail and 9.5kW powershower. They will have ovens, 4-ring hobs and extractor fans, washing machines and fridge/freezers. There will also be a 15L undersink water heater which will supply hot water to the sink and basin in each flat. That's it.

It works well in the other project with no issues on the 69kVA supply. Would I need to consider anything else or are my assumptions incorrect?

James

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#### buzzlightyear

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It would be adviasble to get a spark in to calculate the loading out for you .

#### Spoon

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I have done a similar project in the past where the 69kVA was sufficient for 6 flats. This house is double the size however the electrical demand is the same.

#### Vedb

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Whereas the last project was completed by my electrical engineer. This one, I am doing the calcs myself and so need to provide the network with my numbers. I need to know if it is just as simple as dividing the 69kWA by 6 and have a value for the LL supply etc. How would I go about doing this the correct way ?

#### Spoon

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How would I go about doing this the correct way ?
Whereas the last project was completed by my electrical engineer.
I know you probably want to same money by doing it yourself but if you want it doing the correct way, please see above.

#### Vedb

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Yes, I am aware that getting a professional would be preferable. However, as it sounded fairly straight forward based on having much of the information already, I wanted to know if money needed to be spent on it.

Is there a calculator or online tool that someone can recommend which will churn out values based on input?

#### buzzlightyear

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Yes, I am aware that getting a professional would be preferable. However, as it sounded fairly straight forward based on having much of the information already, I wanted to know if money needed to be spent on it.

Is there a calculator or online tool that someone can recommend which will churn out values based on input
yes us .

#### ipf

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Crack on with it...…..you can always get someone qualified to sort it out when it goes tits up....
Or...….spend to save.

#### PEG

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Hi bud,i do not know the value of 6 London flats,but there should be enough in it,to confirm your loading calcs,using your electrical engineer. He will require the exact figures,for the additional equipment,and,i would imagine,a preliminary drawing,to iron out any surprises,like boosters,fire gear,sewerage pumping,and eight other things i can think of,which i have seen "pop-up" in past projects.

I may be able to give you a jolly analogy,which may assist in understanding any acerbic comments,i feel you may be fielding

#### Vedb

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Thank you all for your responses. While it does seem to me that there is a DIY way to work these things out, I think I will just get a local spark to give me the required details.

Thanks anyway,

James

#### James

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Am I wrong to assume 11.5kVA is enough for each one bedroom flat?

The landlord supply will have just four or five lights and some sockets. The flats will all be electrically heated with 2 x 2kW panel heaters, electric towel rail and 9.5kW powershower. They will have ovens, 4-ring hobs and extractor fans, washing machines and fridge/freezers. There will also be a 15L undersink water heater which will supply hot water to the sink and basin in each flat. That's it.
winter morning,
4kw room heating
0.5kw towel rail
9.5kw shower
3kw kettle
adds up to 17kw, without accounting for anything else. I think 11.5Kw might be a little on the light side.

#### Matthewd29

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Good idea James, will all due respect this had to be correct or you have a big mess on your hands and a lot of money spent, trial and error DIY won't cut it here

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