Ring spurred at origin?

[mattrgee]

Hi all,

DIYer here. My garage has a double socket fed by 4mm2 twin and earth connected to the same circuit breaker has the ring main for the sockets upstairs in the house. The MCB is a B32.

Is the feed in the garage considered a spur from the ring main or is it a separate radial circuit which happens to be on the same MCB? Ideally I'd like to add more sockets to the circuit in the garage (using 4mm2) but is this safe or allowed?

Thanks.

 

[Octopus]

It's a spur so no more sockets can be added ....

If you change the socket for a fused spur, then you can have as many sockets as you like, limited to 13 amps

These sockets must be protected by an rcd

 

[westward10]

It would be considered a spur and being 4.0 its method of installation would dictate whether it could carry 32A and be added to. Spurred points from ring final circuits are normally limited as to the number of points which can be served but the 4.0 clouds that a bit. It sounds like the garage socket has been a later addition and connected to the existing ring final circuit and if the existing circuit is wired using 2.5/2.5 conductors it is not ideal to have differing sizes at the same protective device, are there spare ways in your consumer unit.

 

[Pete999]

If the 4mm2 is on the same circuit breaker as the RFC then it is a Spur, as for adding more sockets to the 4mm2you would need to swap the double socket for a Fused spur unit and add sockets from that spur unit, remember the extra sockets will be limited to 13Amps governed by the fuse in the spur unit.
Another method would be to take the 4mm2 to a seperate CB (providing there is one) and form a 32 Amp Radial to your Garage (assuming it's an atatched Garage), the proviso being is that your Garage would need RCD protection, if the garage is a standalone then a different set of rules apply.

 

[westward10]

The question as to whether this 4.0 can take 32A is down to its installation method. The spur is somewhat unconventional as it stands.

 

[Octopus]

The question as to whether this 4.0 can take 32A is down to its installation method. The spur is somewhat unconventional as it stands.

it's the supply to a 2G socket so the max load is 20a

 

[mattrgee]

The question as to whether this 4.0 can take 32A is down to its installation method. The spur is somewhat unconventional as it stands.

The 4.0 is clipped along a roof joist in the garage, exposed to the air, no insulation etc. The consumer unit is actually in the garage, but there is no space for additional circuits.

We've only been in the house a few months so trying to understand what work has been done previously.

 

[westward10]

it's the supply to a 2G socket so the max load is 20a

I am considering whether it can be added to.

 

[westward10]

The 4.0 is clipped along a roof joist in the garage, exposed to the air, no insulation etc. The consumer unit is actually in the garage, but there is no space for additional circuits.

We've only been in the house a few months so trying to understand what work has been done previously.

Theoretically you could add to it but the best course is to connect to its own protective device but this is obviously not possible.

 

[Pete999]

I am considering whether it can be added to.

It could be if there is a Fused Spur Unit instead of the twin socket, the add some extra sockets, where is the problem with that?

 

[westward10]

The spur is 4.0 clipped direct so in theory if he uses the same size of cable and installation method as the existing he could add direct to it. Personally I would like to see it on its own circuit.

 

[Spoon]

Ideally I'd like to add more sockets to the circuit in the garage

What are you intending to plug into these sockets.
Is the 32A breaker protected by an RCD?

 

[mattrgee]

What are you intending to plug into these sockets.
Is the 32A breaker protected by an RCD?

Yes, protected by RCD. Sockets will be used for drill charging, Henry vacuum cleaner etc.

 

[Risteard]

I would consider it wholly unsatisfactory to have mixed sizes of cable connected in the DB like that. You're practically screaming to get poor connections.

 

[Pete999]

The spur is 4.0 clipped direct so in theory if he uses the same size of cable and installation method as the existing he could add direct to it. Personally I would like to see it on its own circuit.

A spur equates to One double or single socket
A One fused or unfused spur unit
A One fusedspur feeding a Fixed appliance.
The only way you can add more than one socket is on a 4mm2 32 or 30 Amp radial circuit if adding more than one the the cable used must be the same as the circuit is wired in 4mm2, this is the same for a 20Radial circuit wired in 2.5mm2
As the circuit in question is a Ring FC adding more than one unfused socket is not allowed

 

[telectrix]

if the CU is in the garage anyway, why not split the tails with \Henley blocks and fit a "garage board". RCD + 2/3 MCBs. then a fault in the garage will not saffect the house CU andyou would have a spare way/s. a 4mm 32A radial for sockets, 6A MCB for lights.....

 

[mattrgee]

Thanks.

Based on what's been said, is the following an acceptable way forward?

>Replace the existing twin socket with a fused spur unit, fused at 13 amps.
>Add additional sockets from the fused spur unit fed by 2.5.

 

[westward10]

This is somewhat unconventional and is clearly ad hoc, yes it should be on its own circuit as I have also suggested but the limitations of what can be added to this spur is clouded by the cable size, 4.0. Appendix 15 which is informative does not demonstrate the use of 4.0 cables/conductors.

 

[westward10]

This is somewhat unconventional and is clearly ad hoc, yes it should be on its own circuit as I have also suggested but the limitations of what can be added to this spur is clouded by the cable size, 4.0. Appendix 15 which is informative does not demonstrate the use of 4.0 cables/conductors.

 

[Octopus]

Thanks.

Based on what's been said, is the following an acceptable way forward?

>Replace the existing twin socket with a fused spur unit, fused at 13 amps.
>Add additional sockets from the fused spur unit fed by 2.5.

Yes .... And it's going to need to be tested

 

[Andy78]

Sounds like a problem waiting to happen. I'd get an electrician in to do this for you properly.

 

[Spoon]

Sounds like a problem waiting to happen. I'd get an electrician in to do this for you properly.

what??? and spend money???? are you mad??

 

[Pete999]

This is somewhat unconventional and is clearly ad hoc, yes it should be on its own circuit as I have also suggested but the limitations of what can be added to this spur is clouded by the cable size, 4.0. Appendix 15 which is informative does not demonstrate the use of 4.0 cables/conductors.

Yes it does on a 32 or 30Amp Radial circuit
Wired in 4mm2
2oAmp Radial wired in 2.5mm2

 

[Pete E]

if the CU is in the garage anyway, why not split the tails with \Henley blocks and fit a "garage board". RCD + 2/3 MCBs. then a fault in the garage will not saffect the house CU andyou would have a spare way/s. a 4mm 32A radial for sockets, 6A MCB for lights.....

I assume that need to be notifiable under Part P?

 

[westward10]

Yes it does on a 32 or 30Amp Radial circuit
Wired in 4mm2
2oAmp Radial wired in 2.5mm2

I am talking ring final circuits. But yes you could consider this a 4.0 radial so I see no need for a fcu but circuit separation should be employed.

 

[Spoon]

I assume that need to be notifiable under Part P?

Yes mate.

 

[mattrgee]

Thanks all.

Tempted to leave it as is for the time being and not add any additional sockets. There's a bathroom renovation on the cards soon where there is an electric shower running from a dedicated circuit. Once that has been decommissioned I'll ask he electrician to create a dedicated circuit for the garage sockets.

 

[Pete E]

Yes mate.

View attachment 41350

I thought so...I think when work becomes notifiable, its probably cheaper and certainly less hassle to get a suitably qualified Spark in...

 

[westward10]

Adding/altering this existing circuit would not be notifiable.

 

[Pete E]

Adding/altering this existing circuit would not be notifiable.

I was referring to the option of fitting an additional CU for the garage etc that was mentioned earlier in the thread..

 

[westward10]

Okay with you now.

 

[Devonchris]

The more I read this thread the more confusing it becomes.

As far as I see it,

There is nothing wrong with a spur on a Rfc taken from the CU.
Its in the OSG 7.2.2 para 4.

The spur would normally be in 2.5mm2, but the fact that it's in 4mm2 is not a problem. (Might be a big garage, VD and all that)

If the socket is replaced with a FCU then there's no limit on how many sockets can be connected to the load side, as long as your happy with the 13 amp limitation.

As this is not a new circuit then it does not require Part P notification.

 

[Midwest]

I think most have an issue with the termination of 1 x 4mm & 2 x 2.5mm conductors in a singular mcb, and the possibility of the connection not being tight enough?

 

[Devonchris]

Fine, I can see that point. But isn't that down to whoever is doing the installation and not what is allowed and what isn't?

 

[mattrgee]

The spur would normally be in 2.5mm2, but the fact that it's in 4mm2 is not a problem. (Might be a big garage, VD and all that)

Is this because it's on a B32 MCB?

 

[Pete999]

Is this because it's on a B32 MCB?

It's a spur from a 2.5mm2 RFC albeit from the CU, no problem with that, why 4.0mm2 was used is a mystery, it makes no difference to what you can and can't add, a spur is a spur, one twin or single socket only fed directly from the RFC without a FCU involved. Nothing to do with the B32 Amp CB rules is rules is rules.

 

[westward10]

Where is this rule for a 4.0 spur.

 

[Pete999]

Where is this rule for a 4.0 spur.

Where is this rule for a 4.0 spur.

Not one as far as I am aware, Westy. I was just wondering why a 4.omm2 was used, just makes life dificult for the installer.

 

[westward10]

It is an ad hoc addition, no spare ways so whack it on the ring.

 

[Devonchris]

As pete said, there isn't a rule, but there's nothing preventing it. Cable sizing in the guides are the "minimum " requirements.

We don't know the cable size in the RFC that the spur is connected to. The op has never declared that. The whole thing could be in 4mm2. It's pure speculation on our part that's its 2.5mm2 because that's the norm.

 

[mattrgee]

We don't know the cable size in the RFC that the spur is connected to. The op has never declared that. The whole thing could be in 4mm2. It's pure speculation on our part that's its 2.5mm2 because that's the norm.

Will check.

 

[Pete999]

As pete said, there isn't a rule, but there's nothing preventing it. Cable sizing in the guides are the "minimum " requirements.

We don't know the cable size in the RFC that the spur is connected to. The op has never declared that. The whole thing could be in 4mm2. It's pure speculation on our part that's its 2.5mm2 because that's the norm.

And the fact that the OP has mentioned 4.0mm2 on several occasions, but yes the assumption is/was that it is a RFC wired in 2.5mm2 cable. Thanks for pointing that out.

 

[MDJ]

The question as to whether this 4.0 can take 32A is down to its installation method. The spur is somewhat unconventional as it stands.

? sorry can you clarify

 

[Wilko]

Just interested - how long is this 4mm spur cable?

 

[Wilko]

? sorry can you clarify

Hi - I took it as referring to ccc of 4mm - when clipped direct for example it exceeds 32A, but not if in conduit etc.

 

[Spoon]

Just interested - how long is this 4mm spur cable?

Considering the 4mm is connected at one end at the CU (located in the garage) and to a socket at the other end (also located in the garage) I'm presuming it's not that long, unless the garage is massive and the route is silly.

 

[MDJ]

Duel post, no idea why, apologies

 

[MDJ]

Ah okay thanks for the reply, I did wonder, that explains your post
It will be fine though

 

[Midwest]

Is this because it's on a B32 MCB?

Considering the 4mm is connected at one end at the CU (located in the garage) and to a socket at the other end (also located in the garage) I'm presuming it's not that long, unless the garage is massive and the route is silly.

Perhaps its the same guy, who had the bathroom in his bedroom the other day; or was it a bedroom in his bathroom?

 

[Risteard]

I wouldn't agree that the 4mm^2 part of the circuit needs to be considered as an unfused spur from the ring final circuit at all.

In my view it is clearly a hybrid ring/radial final circuit and in no way is it one of the standard circuits.

Assuming that the 4mm^2 cable is afforded overload protection by the 32A circuit breaker then it isn't unsafe to add sockets to the radial part of the hybrid circuit.

Presumably it was done because spare ways were not available or whatever. As I stated before my concern with the arrangement is solely the fact that there is unlikely to be an adequate connection/clamping of all the circuit conductors when they are of varying cross-sectional areas, and for this reason I would consider the arrangement to be wholly unsatisfactory.