Large house rewiring

[u587162]

I'm gutting out my new house as part of a 12 month project. My builder friend will ensure the plumbing and electrics are done by the proper people.

I just want to research and understand the best options here and would appreciate some expert input.

If there are 6 bedroom and numerous other rooms / bathrooms in the house, is it normal to expect to have separate fuse boxes or should I have one giant one that covers every room on every level of the house?

It is still ok for example, to have one cable direct from the main fuse box in the garage to serve another fuse box in the loft which then splits to serve e.g. 3 bedrooms and 1 bathroom with the appropriate RCDs and safety gizmos? I guess ultimately I am asking if it is is ok / normal to "daisy chain" fuse boxes?

I'm looking to do this properly, what high end fuse boards are there at the moment and what are they capable of doing other than the normal task?

 

[ban-all-sheds]

My builder friend will ensure the plumbing and electrics are done by the proper people.

Make sure he does. Friend or no, there are a significant number of builders who do not employ/retain/use "proper" electricians. Or who withold electrical certificates as part of an unrelated dispute. If I were you I'd consider asking my friend to just put you in touch with electrician(s) with whom you deal directly, "rather than me putting you to any trouble, old friend".

If there are 6 bedroom and numerous other rooms / bathrooms in the house, is it normal to expect to have separate fuse boxes or should I have one giant one that covers every room on every level of the house?

No and no.

i.e. it is unlikely that you would need to have multiple CUs if the house is being rewired from scratch, and it wouldn't be normal. But you don't have to have just one large one - if you have a good reason to want multiple ones, then have them.

It is still ok for example, to have one cable direct from the main fuse box in the garage to serve another fuse box in the loft which then splits to serve e.g. 3 bedrooms and 1 bathroom with the appropriate RCDs and safety gizmos? I guess ultimately I am asking if it is is ok / normal to "daisy chain" fuse boxes?

It's never really been OK, in that that's not the best way to do it. If you want multiple CUs then the best way is to have each supplied directly from the meter, via switchfuses, rather than from one of the ways in the "main" CU.

Would a loft be a sensible, convenient place for a CU? Why would that be preferable to having those rooms supplied by the CU in the garage?

what high end fuse boards are there at the moment and what are they capable of doing other than the normal task?

People will have their favourites, but the usual suspects will include Merlin-Gerin, Hager, Siemens etc - basically the makes that tend to be commonly used in commercial environments, not the cheap flimsy stuff built down to a price and sold in the sheds, or as fully-loaded special offers in wholesalers.

As for capabilities - what do you want them to do "other than the normal task" ?

 

[PrenticeBoyofDerry]

It is really up to you, but all services will be distributed from either a main CU or the supply at the service after the main fuse. Normally in a domestic you would expect a single phase supply and be restricted be a 100A fuse.
The first thing you should be looking at, is the number of circuits that would be required to meet your requirements.
Such as:
Lighting upstairs
Lighting downstairs
Outside lighting
Socket upstairs
Socket downstairs
Kitchen sockets
Cooking appliance circuit
Utility circuit
Garage/outhouses/external power circuit
CH and DHW circuit
Shower circuits
Smoke alarms
Intruder alarm
Fridge socket

 

[ericmark]

I remember my son doing a large house was originally a mill and we talked at length about how to split the house into circuits. In the main a consumer unit has a maximum size of 100A and we were uncertain as to if this was big enough. So our method was to use a 160A switched fuse box with three fuses each feeding a consumer unit. Our thoughts were if the supply was not big enough we could easy split into phases or use a larger supply.

However once occupied we found the 100A supply was ample and there was not need for over the 100A supply. Unless using the supply for heating it really does not matter how large the house is it's how many people living in the house which dictates how much power is used.

Some items like washing machine it does not matter if 1 person or 10 people still only one washing machine.

As with industrial premises you often have an option on what power is used, gas, oil, electric or other and selecting to use gas to heat water for showers will reduce the demand for electric in the house.

So with some common sense a 100A is enough what is the problem is volt drop. A single ring final will likely have too large of a volt drop so the designer has to consider how to wire the house. Be it radials, or lollipop circuits or sub-mains that's his job and what he is paid to do. He may for example decide splitting side to side rather than upper and lower is a better option.

But down to basic point the designer has to sign the installation certificate as the person who has designed the installation and although he may look at other examples the buck stops with him. He has to sign that he has designed so that is exactly what he must do.

Where it all goes wrong is where designed for a single family does not matter how big and then multi-families move in as that would likely mean multi-cookers, and multi-washing machines etc.

We split an installation into circuits to:-
(i) avoid hazards and minimize inconvenience in the event of a fault
(ii) facilitate safe inspection, testing and maintenance
(iii) take account of danger that may arise from the failure of a single circuit such as a lighting circuit
(iv) reduce the possibility of unwanted tripping of RCDs due to excessive protective conductor currents produced by equipment in normal operation
(v) mitigate the effects of electromagnetic interferences (EMI)
(vi) prevent the indirect energizing of a circuit intended to be isolated.
It does not only mean multi MCB but also Multi RCDs and what becomes a problem is consumer units are designed to only have either 2 RCDs or RCBOs which work out expensive. So using Multi consumer units allows you to use more RCDs but there is also the question of what is permitted.

In domestic we use type tested distribution units although fitting a fused switch may work it raises the question is it permitted? As does using any other commercial distribution unit. One can argue until the cows come home but as I said to start with who ever signs the paperwork has to decide what he thinks is reasonable.

 

[OwainDIYer]

6 bedrooms isn't really a large house.

You wouldn't want fuse boxes (consumer units) hidden away in the loft. Usually you would have one CU for the whole house, but if the cable layouts are such that it's better to have a submain (to reduce voltage drop on long circuit cables) then typically one CU at each end of the house would be done e.g. "east" and "west".

Things you might want in consumer units:

doorbell transformer
outside lights timeswitch or photocell relay
timer / contactor for electric heating if used
solar panel feed-in metering