Single socket circuit.

[Mjsanders]

Hey all.

We've just moved house and I want to put in a new circuit in just to service a computer server and network attached storage (NAS), luckily there's a spare circuit on the distro board (new RCD type).

A couple of questions.

1) If it's only going to have one socket, does it need to be a ring?

2) Under the current regs, can I do this - connect to the RCD on the board. I'm happy doing it (lots of install experience in TV studios) but not qualified.

Many thanks.

Michael

 

[mbga9pgf]

can you legally do it - No.

Can you do it - no. Not by connecting to the RCD. You need an MCB between the RCD and Cable

 

[Mjsanders]

Mmm interesting..

Apologies I got my mcb and Rcds terminology wrong.

Not all the circuits go via the RCD. Only some of the sockets go via the RCD. The rest are just MCBs on the board.

There is a spare MCD on the board with nothing connected to it.

Oh well - time find a friendly spark!

 

[PrenticeBoyofDerry]

1) If it's only going to have one socket, does it need to be a ring?

No it can be a radial circuit

2) Under the current regs, can I do this - connect to the RCD on the board. I'm happy doing it (lots of install experience in TV studios) but not qualified.

I assume this is a domestic installation?
You can't directly connect it to the RCD but you can via a MCB that does have at least 30mA RCD protection (as socket outlets require RCD protection).
In law you can do this yourself, but as it is a new circuit it will need to be notified to building controls prior to installation, which usually comes with a substantial fee, that would make it a more logically move, financially and safety wise, to get a self cert electrician to do the install.

 

[ericmark]

Since you seem to want a dedicated supply I would assume it's so it does not trip when the rest trip?

The main reason for any sockets to trip is for the RCD rather than MCB to open so to do want you want either you would need an RCBO which is a RCD and MCB combined which in turn is supplied before the main RCD or needs to use special cable normally Ali-tube which does not require RCD protection and the socket has to be marked for server only.

Either way it would need a consumer unit designed to have some circuits not through the main RCD and work on consumer units is notifiable so just not worth doing as DIY.

Likely both better and cheaper to use an UPS which is a device with a battery which will keep things running for so long with a power cut. This would not need notifying so you could do it yourself.

As to rings and radials you can have either but normally when supplying one item we would use a radial system. Common is a B16 or B20 MCB supplying them rather than the B32 often used with a ring. With one socket a B16 would be ample.

But first question is why you want a dedicated circuit?

 

[SimonH2]

IMO the question is still too vague to be sure. But, as far the regs go, I think one could argue that if there's an MCB in the board then a circuit exists - so adding a socket to it would be adding to an exiting circuit and so not notifiable (unless in one of the special location/special installations that are restricted). Since one could assume the computer etc (probably) aren't going to be in a bathroom or kitchen then then I see no problem there.

Next we need to know what rating the spare MCB is, and which side of the board it's on - RCD protected or not. Perhaps the OP could add this information.

If the MCB is on the non-protected side, then I believe a radial off that would be allowed as long as all the restrictions on cable routing are observed. IIRC (and I'm sure someone will correct me !) it's OK if the cable is surface mounted (so visible), buried more than 50mm deep, or protected by earthed metal conduit. The outlet on the end would need to be RCD protected.

Cable size, and what can be on the end of it, would depend on routing and rating of MCB.

 

[ban-all-sheds]

can you legally do it - No.

Wrong.

 

[plugwash]

1) If it's only going to have one socket, does it need to be a ring?

Radial circuits are just fine as long as the cable is appropriately sized to the overcurrent protection.

2) Under the current regs, can I do this - connect to the RCD on the board. I'm happy doing it (lots of install experience in TV studios) but not qualified.

a RCD only provides protection against faults to earth, to provide protection against overcurrents (both overloads and short circuits) you need a MCB. A RCBO combines both functions.

All circuits absoloutely MUST have overcurrent protection. Socket outlets "for general use" require RCD protection as do most concealed cables*

In my experiance RCDs are far more prone to unwanted tripping than MCBs so having a dedicated MCB for your computer stuff while sharing an existing RCD seems kinda pointless.

* exceptions include cables burried more than 50mm deep, cables enclosed in earthed steel conduit, special cable types that include an earthed metal layer such as MICC and flexishields and cables in an installation that is under the supervision of a skilled or instructed person.