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Hi All, Making some alterations in an existing flat and scratching my head about required supply to flat. It is all electric, 1 bed, 1 bathroom.
Electric shower 9.5kw
Instantaneous Water Heater 9.5Kw
Cooker Oven & Hob 6Kw
1 Ring main
3 Electric Heaters not E7 4.5Kw
Lights <600w

I have used OSG diversity allowances and still come to over 150A! I currently have a 60A fuse protecting a 16mm T&E submain, which I am concerned about hence the calculations, I know its unikely to draw 150A but wondered if anyone can give a bit of guidance on supply requirements.
I know shower and water heater will only be on for <20mins at a time but think what if one person showers while the other does washing up, makes tea and turns heating on!

I am also aware the submain run through the communal area should be RCD protected due to being buried <50mm. Not necessarily avoiding replacing submain but something to carry my 150A would be of epic proportions and require a DNO upgrade of incoming supply.
 
When you say E7 on separate supply, it was on the same 60A fuse though? Any chance you can convert the HW to tank with 3kW immersion?
 
There were 2 storage heaters which are not fed by the con unit in the flat, I assume they were wired back to the mains cupboard where the cutout, meters and isolators reside (basement) flat is 3rd floor.
Client has chosen the all electric setup, trying to work out what I should recommend they do.
 
Why was the E7 taken out. This would have kept the loading within parameters.
If there is no gas in the property this is what E7 is for.

Agree a 3kw immersion would help. Also reduce showers power to a 8KW.
Do heaters need to be 4.5kw?
Has a calculation been done to suggest this is what is needed for this size flat?
Will a 3 KW heater be better?
Even doing these things I doubt 60A main cut out would be adequate.
Go back to E7 and instal the new quantum E7 heaters that are really good.
 
The main issue is the shower and instantaneous water heater for which you cannot apply diversity to
.
Use a priority unit with the shower getting prority, then you will only need to allow for 9.5kW demand for both of these. You can likely make the rest work out then.

You can buy them here or make up your own with an enclosure, CT relay and contactors.

Priority & Non-Priority Shower Units | Electrical News | Meteor Electrical Ltd. - http://www.meteorelectrical.com/news/consumer-units/priority--nonpriority-shower-units/801526994
 
Thank you all, with diversity applied per OSG i was still getting 150a as all the main loads are heating elements.

I wasn’t aware of the priority units, so will take a look here. New SWA submain going in now.
 

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