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.

 

[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.