Big job, many circuits.

[Patch]

Evening chaps. Long time reader first time poster right here, big fans of your work and all and I'm hoping to call upon your collective experience and might with a rather large job I seem to have "lucked" my way into.


The property is a grade 2-star listed building in the fair county of Rutland. In total there are about 22 rooms (subject to the whim of the owners), 5/6 bedrooms, 3 bathrooms (2 e-suite), drawing room, study, lounge, kitchen, dining room blah, blah, blah the list goes on.
The main house was last refurbished (read: bodged) in the late 50's and has fallen into a state of disrepair in recent years. The job started at the start of April and I'm now finding that we're ready to start carcassing. I've been given no wiring specifications, I've had to push for a lighting design so I'm doing most of it off my own back. Of course, I've never tackled anything on this scale


My main problems are:
** The list of final circuits has spiralled to somewhere in the region of 20. Mostly lighting. Five are interior (two upstairs, three down), one for exterior security a second for exterior decorative. Power has similarly be split into five circuits (again, two up, three down) alongside which are round pin 5 amp sockets (for lamps) of the same arrangement and finally a dedicated fridge/freezer and cooker feed (reported to run off a 13 amp plug, but I figure only just). Oh, and an immersion back-up if the bio-mass boiler fails. Questions? Good.
Is this excessive? On one hand it makes good sense, on the other... well, 20 is a lot!
Most of the fixed lighting will be ELV in various forms (LED, halos, CFTs) with one or two decorative pendant fittings. Without knowing exactly what's going where, is there a better way of guestimating other than the old "assume 100 watt per fitting" rule of thumb? At the moment that suggests 10 amp breakers which when it comes down to it, will probably be way OTT.
I'd like some clarification for the 5 amp round pin sockets. My instinct would be to set them up as a ring main on a 6/10 amp breaker with 1.5mm T+E. Is this correct?
Is having enough ways as simple as running two CCU's and feeding them off henley blocks?




**The house will be heated with hot-water over (yes, over) floor heating. This means that anything under floorboards will be inaccessible once the heating is in place. It has been suggested to me that a gap around the walls could be sufficient to run cables and leave them accessible in a worst case scenarios. 6mm thickness of ply provides the FFL. Is that sufficient mechanical protection (bearing in mind there'll also be a skirting on top of it)?


** Even with diversity, I'm looking at a maximum demand of around 150 amps. Do I just need to get the distributor to upgrade the supply?


Right, pub o'clock! Thanks in advance for any insights! I'm sure I'll come upon more stumbling blocks.

 

[IQ Electrical]

Right Sir, you just pop to the pub Sir, when do you want the design done by?

Running all the way Sir......

Welcome to the forum!

 

[Octopus]

Welcome.

IMHO you need to get a local "mate" with years of experience to do this with you!

 

[sparks_114]

Right Sir, you just pop to the pub Sir, when do you want the design done by?

Running all the way Sir......

Welcome to the forum!

LOL, good old IQ, always on top.

 

[alli]

Depending on building layout, you may find it easier to have 2-3 or more consumer units at different parts of the house, which means you only have to run one larger cable to that point rather than running all the cables back to one point, which may end up being a cheaper alternative. This will also mean that any future alterations can be done to a local board rather than lifting the floor with the heating system.

I would also give some consideration to the cables running alongside the underfloor heating, What will the ambient temperature be? When calculating conductor size will the CSA need to be increased to a size that is expensive to install? Could an alternative cable run be employed?

If the cable route will be under the floor that will become sealed, could you run a large conduit/ducting which will allow future installation of cables?

On the estate I work on we have a large 6 bedroom house with a three phase dist board that feeds 7 sub boards, One each for North, East, South and west sides of the building one dedicated for the kitchen, one for the scullery/laundry room, one for the boiler room. This is a very expensive way to do it!! but works very well.

 

[cadspark]

20 circuits on a house that size is not excessive. I put 10 into a one bedroom house recently.

2 split load ccu's with dual rcd is a good option split like you say with henley blocks. Ideally you will have an isolator before the split which the DNO should be able to fit for you.

If there are no electric showers or heating then the supply should be adequate as most appliances will be low draw items. Might be worth asking DNO what size incomer is and request an upgrade to 100 amps if it is not already assuming the supply cable can take it.

I would wire the 5 amp round pin sockets as a radial. Whenever i've fitted them they have been designed to come on with a standard wall mounted light switch.

 

[SirKit Breaker]

Patch,

Well done landing the nice big job and i hope it goes well for you.

I agree with murdoch, this is one job where a bit more help knowledge and experience won't go a miss. Not saying you aren't up to it, but is a big job for one man. I know i would want some help if it were me doing it.

Cheers..........Howard

 

[Dunc]

20 circuits for a property of that scale is not excessive. I'm working on a property at Burley on the Hill (not far from you ) that for some unknown reason has 3 lighting circuits feeding one bathroom! This appears to be the norm throughout the house so the main consumer unit is a 48 way single phase job. That is the definition of excessive!

As for the your install have you thought about running a couple of submains to additional consumer units better located to reduce the lengths of your final circuits. I did this on a recent rewire in Werrington (5 bed, 19th century, grade 2 listed house) where i had 3 consumer units. One in the garage which fed everything local to it and two more in the understairs cupboard which was nice and central for everything else including a decent route straight up to the first and second floors.

Out of curiosity which village are you working in? I'm from that neck of the woods (Stamford) and have done work in Riddlington, Burley and Oakham fairly recently.

 

[Patch]

Thanks for the replies. I would accept that a little more experience wouldn't got amiss here, but it really was too good an opportunity to turn down. I do have experienced hands to call on, but they're back home and far too busy themselves, the internet is far closer.

A submain or two are definitely something I'll think about. That is what was done before but I'd assumed it was more to do with the house being separated in to distinct apartments.

If I don't go to the pub, I don't eat. I'm not from round here, there's no one to cook dinner! (Not to mention it's 7-8pm before we finish.)

 

[MarkieSparkie]

Hi, welcome to the forum.

 

[Patch]

Question about submains. When allowing for diversity, should it be applied to the whole house, or on a per-board basis as it were?

Dunc, we're in Braunston.

 

[sparks_114]

Question about submains. When allowing for diversity, should it be applied to the whole house, or on a per-board basis as it were?

Dunc, we're in Braunston.

Whole house/per service head.

 

[Sparky Ninja]

Do I just need to get the distributor to upgrade the supply?

You tell us? You've not really mentioned it.