QUERY ON LARGE HOUSE ELECTRICS

[jon26]

I am completely gutting a large property which will need mostly new electrics (i am not an electrician) but I am curious as to how the electrics will be put in.

Basically there is a main house 5 bed detached property with a link to a small annexxe guest area. 3-phase enters the house and currently the main distribution board is in the main house. This position of distribution will most likely remain, however, will the electrics for the annexxe area be best taken from this point or is it possible/normal to run a sub-main to a small distribution board nearer to the annexxe just to control that area (it is probably about 25m away)?

Thought I'd ask the experts...

 

[sparkyspike]

You can fit a sub main (eg 63A switchfuse unit) by your existing fusebox and then run suitable cable to a fusebox in the annexe. Whether you use a separate phase incomer or the same phase as the rest of the house depends on things such as your max load, availabilty of 3 phase etc.

 

[ban-all-sheds]

Perfectly possible, and IMHO ought to be the "normal" solution that anybody considers.

Are you project managing the refurb, and getting in contractors to do the work, or doing some of it yourself, or handing the whole lot over to a builder?

 

[plugwash]

I would definately suggest running a submain so that RCD protection for the annex can be in the annex and to allow the annex supply to be metered or even moved onto a completely seperate supply if desired in the future.

 

[hairyben]

Perfectly possible, and IMHO ought to be the "normal" solution that anybody considers.

While the distances involved can lend themselves to it, one has to weigh it against the probablity that a large, luxury house will contain someone who won't know or care where his extra fuseboards are, so there's a good arguement in terms of "usability" to centralise everything where it can be easily located...

 

[jon26]

Perfectly possible, and IMHO ought to be the "normal" solution that anybody considers.

Are you project managing the refurb, and getting in contractors to do the work, or doing some of it yourself, or handing the whole lot over to a builder?

What does IMHO mean? I assume the 'normal' solution would mean to take the supply for the annexe from the distribution board in the main house although it is some distance away??

The sub-main seems the most logical way forward, with a sep. board in the annexe, I have also found out that a 3-phase supply is also require to the annexe for some equipment in the garage below, would this effect the decision?

I will be getting contractors to carry out the work.

 

[ban-all-sheds]

What does IMHO mean?

In My Humble Opinion

I assume the 'normal' solution would mean to take the supply for the annexe from the distribution board in the main house although it is some distance away??

I would hope it was to split the tails and go through a switchfuse to supply a DB in the annexe.

The sub-main seems the most logical way forward, with a sep. board in the annexe, I have also found out that a 3-phase supply is also require to the annexe for some equipment in the garage below, would this effect the decision?

It would mean that unless the main board is a TP one you won't be able to come off that, and now you'll need a TP switchfuse.

I will be getting contractors to carry out the work.

Make sure they are real ones, not just Domestic Installers...

 

[jon26]

Can the 3-phase sub-main be run internally through the main house?

 

[RF Lighting]

Probably.

You really want to be asking your electrician these questions, as he can see the job, and we can't.

 

[Spark123]

Do you need a 3 phase sub main or will a single phase one be adequate?

 

[RF Lighting]

I have also found out that a 3-phase supply is also require to the annexe for some equipment in the garage below

 

[ban-all-sheds]

How much are 1P -> 3P convertors?

Depending on the load might it be cheaper to use one of those than to run 3 phases to the annex?

 

[jon26]

Just found out there is an armoured cable rising up near the annexe that was put in some time ago. It isn't feeding any DB's its just coming out of the ground with a few wires coming out of the end.

Is this likely to be a single-phase cable, would there be another cable with it if it was 3-phase?
I know its a bit tricky as you havent seen it, but I just wanted a better idea before I get a sparky in.

 

[ban-all-sheds]

Is this likely to be a single-phase cable,

How many cores does it have?

And what size is it, and whence does it originate?