Turning off a ring main

[happypig]

I'm refitting a room to use as an office and I'd like to be able to turn a lot of stuff off with a single wall switch rather than scrabble around under the desk.

I'm going to put the office on a separate circuit breaker in the consumer unit and once the cable gets to the office I will split the supply with one side going directly to switched sockets and the other going via a wall switch to unswitched sockets.

Is this feasible, and what sort of wall switch would I need ?

(also, anyone know of a USB hub that can be mounted in a standard size back box ? )

 

[JohnD]

use a radial.

 

[ColJack]

you'd need a 45A switch if you're not fusing the ring down.. but at which point it becomes a spur and you can't take more than 1 double socket from a spur unless it's fused down..

you might get away with it if you use 4mm cable to spur off the ring, but then why bother making it a ring, just make it a 20A radial straight back to the board.. that way a 20A switch can be used and it's just a branch off the radial..

20A is plenty for a small home office, most things only taking an amp or so to run..

as for a usb hub that fits a backbox, why? i dare say you could modify one of the smaller ones to fit into a double backbox but it would still need to be powered if it's that type.

oh and since this invilves new circuits, it's notifiable under part P of the building regulations..

 

[JohnD]

short answer or long answer

 

[happypig]

when you say radial do you mean run cable from fusebox to office switch and from there :

1. go socket to socket to socket and back to switch

or

2. go to each socket separately (switch to socket A, switch to socket B, switch to socket C etc)

Can I run two cables from the same breaker in the fusebox, one feeding a normal ring and the other feeding the radial or do I need two separate breakers ?

And I realise it's part P; fortunately I have a friend who will inspect and connect for me and issue me a chitty.

As for USB hub in a backbox, just to be tidy and have as few cables and boxes on the desk.

 

[JohnD]

1) but you don't return the radial to the switch. it is not a ring.

3) no.

 

[ColJack]

radial. 1 cable into the room, then to each socket in turn. no need to go back to the first socket..

you can treat the switch as one of the sockets and "branch" off from there to the controlled sockets.

1 radial should be fine unless you intend to put heaters and kettles in there with you..

and no you can't put 2 cables form the breaker to the radial and to a ring..

you can however put 2 cables from the breaker to 2 sepertate radials as this just counts as a "branch" at the breaker.

it might be a better idea to do that anyway as you'll need to use high integrity earthing and connecting the earths together at th end of the radials is an acceptible way of providing this..

( do a topic search on high integrity earthing )

I use the term "branch" because some people still debate whether a radial can have spurs..

if you have a friend who will do the part P for you . it might be best to involve him in the design of the circuit as he'll be the one risking his neck on your workmanship..
even if you're doing it all yourself, get him to tell you what to put where, what size cable and so on..

 

[happypig]

Not planning on Heaters/ kettles or anything but I will have

switched :
1 x PC
1 x Laptop
2/3 external HDD
1 set speakers
1 DAB radio
1 KVM switch
1 Portable TV
1 Printer
1 Desk Lamp
1/2 USB hubs

Permenantly on :
1 Router
1 Telephone (mains powered call router on it)
1 Laptop
1 phone charger
Possibly others

So I need at least 13 switchable sockets as well as 6 permenantly live sockets.
(It's still better than commuting though..)

So to clarify, I run cable from fusebox to junction box and split it there, taking
1.permanant live to three double sockets
and
2. to switch, from there to seven double sockets.

 

[happypig]

if you have a friend who will do the part P for you . it might be best to involve him in the design of the circuit as he'll be the one risking his neck on your workmanship..
even if you're doing it all yourself, get him to tell you what to put where, what size cable and so on..

that's probably the best idea I've heard, dunno why I didn't think of it myself

cheers

 

[ColJack]

no need to use a JB ( and preferable not to since it's just another connection that needs to be checked )

cable into the room, to the switch, from the live side of the switch to the 3 uncontrolled doubles, then from the switched side of the switch, to the controlled 7 doubles..

although, what you describe could probably just be done with 3x 5 or 6 way extension leads that you plug in to the sockets above the desk.. ( and might be best since you can get the surge protected ones that have insurance with them.. )

you won't need heaters with all that electronics equipment..

 

[industryspark]

noticed you mentioned phone charger as permenetally on, just a note on this, i dont know if you intend to leave it plugged in and continoulsy switched on but if you do i wouldnt.....

i have a cousin in the fire brigade and he's been to quite a few fires started apparently by phone chargers left plugged in. not sure how much of a worry factor this should be considered but best not left plugged in and switched on imo.

 

[ban-all-sheds]

Can't for the life of me imagine why you'd want a phone charger switched on apart from when you were charging the phone....

I'd suggest that a small UPS would be useful for the comms gear, and anything else you'd like to avoid losing in a power outage.

Sockets in dado trunking will be a lot more convenient than ones under the desk.

Talking of desks - if you don't want to spend the money for a proper one an excellent alternative is Spur uprights every 500-600mm and a length of kitchen worktop on deep brackets. Ideal then for shelving above the desk too.

As for USB hub in a backbox, just to be tidy and have as few cables and boxes on the desk.

Let us know here if you find such a thing - I despair of the desire seemingly shared by every hub manufacturer in the world to make their products smaller and smaller - as you say you end up with stuff all over the desk, and the damn thing never stays in one place because it resists movement much less well than the cables.

I want one designed to screw to the wall....

 

[Click-Sure]

OP @ BAS,

I had the same issue with featherweight USB hubs.

The solution, a four port USB 2 controller card into a spare PCI slot in the back of my pc, costs a little more, but well worth it. That is if you have enough spare PCI slots. (not applicable to laptops, allthough PMCIA versions may exist)

 

[ban-all-sheds]

Plenty of spare slots.

No easy access to the back of the PC.

But it's not my deskside PC where I need a hub - how well does your system replace a hub used by another computer, e.g. a laptop with printers, keyboard, mouse, external HDD.....?

 

[regsmyth]

noticed you mentioned phone charger as permenetally on, just a note on this, i dont know if you intend to leave it plugged in and continoulsy switched on but if you do i wouldnt.....

i have a cousin in the fire brigade and he's been to quite a few fires started apparently by phone chargers left plugged in. not sure how much of a worry factor this should be considered but best not left plugged in and switched on imo.

So when are they going to tell the public not to leave their chargers plugged in? Mine is plugged in to an unswitched multiple extension under my bed, and probably kept nice and warm with a thick layer of that special underbed dust. Every few days I grope around, fish out the cable and stick it in (this isnt a euphamism).
Is it just me?