Sockets on non-ring circuit & changing circuit purpose

[killercowuk]

Hi all,

I have been renovating an old flat from around 1890 (in Scotland). We recently had the consumer unit upgraded to an RCD protected one and fortunately all existing wiring appeared in good shape (redone around 1980s we believe). At the same time we removed an old water heater and tank which was already disconnected and unused - so wasting space.

I am currently looking to reuse the water heater circuit for the sockets in a room to become my office. I've got some computers and a server which I run 24x7 that I would ideally like to have on a circuit seperate from the lights and ring main.

So 2 concerns came to mind with this and hoping that they can be dispelled by some ever helpful folks on these forums:

First of all, is there any issue (according to all BS regulations etc.) with all the sockets in this room NOT being on a ring circuit and instead be connected on the water heater connection as a radial circuit?

Secondly, is changing the purpose of the circuit (from water heater to office sockets) of any issue from a Building Control/Planning permission point of view (in Scotland)?

Thanks in advance.

 

[EFLImpudence]

First of all, is there any issue (according to all BS regulations etc.) with all the sockets in this room NOT being on a ring circuit and instead be connected on the water heater connection as a radial circuit?

No.

Secondly, is changing the purpose of the circuit (from water heater to office sockets) of any issue from a Building Control/Planning permission point of view (in Scotland)?

No, just label the consumer unit appropriately.

Also, if the CU has room you may like to connect the circuit to its own RCBO.

 

[killercowuk]

Great, thanks for the quick reply. Much appreciated.

Also, if the CU has room you may like to connect the circuit to its own RCBO.

Excellent recommendation! Hadn't even considered. Thanks again!

 

[JohnW2]

First of all, is there any issue (according to all BS regulations etc.) with all the sockets in this room NOT being on a ring circuit and instead be connected on the water heater connection as a radial circuit?

As you've been told, that's fine so long as the rating of the MCB ('breaker') protecting the circuit is not too high to protect the cable concerned. In practice, that usually means that the MCB would have to be a maximum of 20A (possibly 25A if you could find one) if the cable is 2.5mm², or 16A if it is 1.5mm² cable - and the total current you could draw from all the sockets would obvioulsy be limited to the rating of the MCB.

Kind Regards, John.

 

[EFLImpudence]

Yes, I was assuming/presuming it would still be the 16A MCB of the immersion circuit.

 

[JohnW2]

Yes, I was assuming/presuming it would still be the 16A MCB of the immersion circuit.

True - but you did also suggest the possibility of changing the current protective device to a new RCBO (of unspecified rating)

Kind Regards, John

 

[EFLImpudence]

That is true, I did but thought further advice may be sought about that.

 

[killercowuk]

Hi guys,

Just to clarify, yes its currently a 16A rcd protected circuit wired using 2.5mm2 cabling. Will be looking into sourcing a 20A MCB to go with new RCBO.

But thanks for checking up on it John

 

[JohnW2]

Just to clarify, yes its currently a 16A rcd protected circuit wired using 2.5mm2 cabling. Will be looking into sourcing a 20A RCBO. But thanks for checking up on it John

Before you rush out to get an RCBO, you need to make sure that your CU can accommodate it. To be able to accommodate an RCBO, your CU needs to have provision for installing a device which is not protected by any of the RCDs - and by no means all modern CUs have that facility (at least, without appreciable 'modification').

If you discover that an RCBO is not really an option, then you could at least upgrade the 16A MCB to a 20A MCB.

Kind Regards, John

 

[EFLImpudence]

sourcing a 20A MCB to go with new RCBO.

An RCBO is a combined MCB and RCD.

 

[JohnW2]

sourcing a 20A MCB to go with new RCBO.

An RCBO is a combined MCB and RCD.

... that quote from killercowuk was obviously after it had been edited. You'll see the pre-edit version in my response above, and that just referred to sourcing a 20A RCBO. However, as I indicated, despite the well-intentioned suggestion, the OP's CU may not be able to accommodate (easily or at all) an RCBO.

Kind Regards, John

 

[killercowuk]

Hi John and EFL,

Thanks for follow up. Sorry yes for some reason I had the impression the RCBO would be a direct replacement for an RCB (ie. could be swapped in - potentially across more than one circuit). Following further research I understand they do both jobs on individual circuits (which makes more sense!).

Regarding my CU - I had a friend who is a spark (but unfortunately hard-pressed for time at present) to carry out the upgrade and still have the packaging.

Screfix sells the same model, fyi:
http://www.screwfix.com/p/bg-6-way-high-integrity-dual-rcd-consumer-unit-6-mcbs/59209

Its supports up to 6 circuits and came with 2 RCDs which have currently been assigned to:

RCD1: Lights, Ring Main and Water Heater.
RCD2: Cooker, Shower and one unused MCB.

Packaging says it supports "up to 4 unprotected circuits" and I recall there being the bus bar that could be cut to whatever lengths/sections required.

Do you think this CU would be flexible enough to support an RCBO?

My thoughts are with the unused 16A MCB removed this could give the extra space for RCBO.

I would probably wait until I could get the professional back out but good to know your thoughts.

 

[JohnW2]

Screfix sells the same model, fyi:
http://www.screwfix.com/p/bg-6-way-high-integrity-dual-rcd-consumer-unit-6-mcbs/59209
Its supports up to 6 circuits and came with 2 RCDs which have currently been assigned to:
RCD1: Lights, Ring Main and Water Heater.
RCD2: Cooker, Shower and one unused MCB.
Packaging says it supports "up to 4 unprotected circuits" and I recall there being the bus bar that could be cut to whatever lengths/sections required.
Do you think this CU would be flexible enough to support an RCBO? My thoughts are with the unused 16A MCB removed this could give the extra space for RCBO.

Yes, that sort of CU could accommodate an RCBO - but, as you imply, that would probably need a bit of reconfiguration of the busbars etc.

I have to ask whether it's really worth the effort. I know that EFLI's suggestion about the RCBO was well intentioned, but I'm not really sure there's a lot of point. Far simpler to just change the water heater's 16A MCB for a 20A one (or even not bother to do that, if 16A would be enough for your new sockets) - which is a straightforward job.

Kind Regards, John

 

[killercowuk]

Yes, that sort of CU could accommodate an RCBO - but, as you imply, that would probably need a bit of reconfiguration of the busbars etc.

Great, thanks for confirming.

I have to ask whether it's really worth the effort. I know that EFLI's suggestion about the RCBO was well intentioned, but I'm not really sure there's a lot of point. Far simpler to just change the water heater's 16A MCB for a 20A one (or even not bother to do that, if 16A would be enough for your new sockets) - which is a straightforward job.

It seems like a bit of work - agreed - however I do appreciate EFLI's suggestion as the equipment (server and computers) being protected may(?) justify it. I do IT work from home and have a server and computers with valuable (sentimental and business) data on them (yes - I have off-site backups). If there are steps I can reasonably take to minimise risk to this room from external sources (be they from within or external to the property) then this may be worth a couple of pints for my spark and a £30 rcbo?

 

[EFLImpudence]

I do appreciate EFLI's suggestion as the equipment (server and computers) being protected may(?)

It's not their protection which may be the prime intention or requirement.

It is the fact that a lamp popping may cause the RCCB to trip taking out half the house and your equipment.

As new sockets must be RCD protected (unless you contend they are for a specific purpose which may be difficult to justify and ensure) an independent RCBO for that circuit only would be beneficial.