Two story extension

[amlu]

without seeing the job. my first thought would be split the tails, 16mm SWA to 2nd CU, then treat extension as a separate set of finals. run the shower from the C/H boiler, then that's 40A that you can forget. fit a 80A KMF for the 2nd CU, ans a 100A isolatoer before your henleys, so there's single point isolation for the whole property.

^^^that, its under £200 in materials if you shop around. not a massive sum and will make your job easier. plus people living in the extension wont have to knock on others door if something trips etc...

 

[djelectric]

without seeing the job. my first thought would be split the tails, 16mm SWA to 2nd CU, then treat extension as a separate set of finals. run the shower from the C/H boiler, then that's 40A that you can forget. fit a 80A KMF for the 2nd CU, ans a 100A isolatoer before your henleys, so there's single point isolation for the whole property.

This is what I initially planned to do, but was worried about diversity.. Using common sense and looking around her house I am very confident that she never uses anything near the calculated sums I've come to.. (Re-calculated again today using the OSG, got around 50A which is fine because the extension will have the exact same circuits excluding the immersion.).

The lady lives on her own, has central heating, immersion is never used, there aren't any major power consuming items in the house other than the typical oven and immersion. Existing installation is up to scratch and was tested 2 years ago. No paperwork present though just going by the sticker on the CU.

So Murdoch, you reckon it's ok to just add all CBs and multiply by .25? Even though the OSG states otherwise.. I suppose it is only a guide.. And does leave me with a more realistic number..

I didn't get round to visiting today, have been calculating using pictures of the place.

 

[telectrix]

stick a clamp meter on one of the tails. switch on everything you can. a quid gets you 10 if it's over 40A ( shower excluded)

 

[Octopus]

This is what I initially planned to do, but was worried about diversity.. Using common sense and looking around her house I am very confident that she never uses anything near the calculated sums I've come to.. (Re-calculated again today using the OSG, got around 50A which is fine because the extension will have the exact same circuits excluding the immersion.).

The lady lives on her own, has central heating, immersion is never used, there aren't any major power consuming items in the house other than the typical oven and immersion. Existing installation is up to scratch and was tested 2 years ago. No paperwork present though just going by the sticker on the CU.

So Murdoch, you reckon it's ok to just add all CBs and multiply by .25? Even though the OSG states otherwise.. I suppose it is only a guide.. And does leave me with a more realistic number..

I didn't get round to visiting today, have been calculating using pictures of the place.

I think the OSG thinks that all houses have a maximum of 6 way CU's! - so the guidance is way out of date IMHO.

 

[djelectric]

stick a clamp meter on one of the tails. switch on everything you can. a quid gets you 10 if it's over 40A ( shower excluded)

Sounds like a plan, will give it a go. Thanks

 

[amlu]

connecting to the existing circuits means messing up at old ladies` house, lifting hundred years old carpets and wardrobes to get into the cables, plenty of power cuts etc. not worth bothering.

 

[bigspark17]

Run a submain into extension and wire all new extension circuits to there, dont over complicate! Is all bonding in place, and are there smoke alarms in house are 2 more important questions that spring to mind?

 

[Midwest]

This is what I initially planned to do, but was worried about diversity.. Using common sense and looking around her house I am very confident that she never uses anything near the calculated sums I've come to.. (Re-calculated again today using the OSG, got around 50A which is fine because the extension will have the exact same circuits excluding the immersion.).

The lady lives on her own, has central heating, immersion is never used, there aren't any major power consuming items in the house other than the typical oven and immersion. Existing installation is up to scratch and was tested 2 years ago. No paperwork present though just going by the sticker on the CU.

So Murdoch, you reckon it's ok to just add all CBs and multiply by .25? Even though the OSG states otherwise.. I suppose it is only a guide.. And does leave me with a more realistic number..

I didn't get round to visiting today, have been calculating using pictures of the place.

Have a look at this vid, to give you a bit of a guide; https://www.youtube.com/watch?v=Wq0uODypaGI

 

[djelectric]

Thanks mate, already watched this this morning.. Very helpful bloke.

Situation looks good, going to fit a second CU in extension, can go ahead and sort an estimate now. Thanks for the help everyone, hugely appreciated!

 

[Octopus]

Thanks mate, already watched this this morning.. Very helpful bloke.

Situation looks good, going to fit a second CU in extension, can go ahead and sort an estimate now. Thanks for the help everyone, hugely appreciated!

I would go with a small rcbo board.

 

[7029 dave]

I would go with a small rcbo board.

So would I.

 

[Guest77]

.

 

[djelectric]

Sorry to come across thick, but I don't get the joke MDJ.

Bigspark, thanks for the advice, wasn't trying to over complicate, just wanted to make sure it's done correctly. I'm a newcomer to this particular situation so I'm paying extra attention to details that I'm not so familiar with. Yes water and gas bonding in place and adequate. Tails also been upgraded and suppliers earth also adequate. All new stuff.

 

[Amp David]

Separate consumer unit in extension every time. If its got its own front door then electrically i'd treat it as a separate dwelling.