Do I need a fused spur

[brianw3706]

Hi,
Found this forum courtesy of Google.
The wife wants a tumble drier, but she's decided there's not enough room in the house so it will have to go in the garage.
The garage is supplied from the house by what I assume is a spur,
(can only see one cable coming into the garage).
The cable goes into a consumer unit with two outlets,
one for lighting and one for power.
I currently have one double socket on the power spur,
which I use for power tools etc, but would like to add another for the drier,
so I don't have to keep swapping plugs, and if necessary
use power tools while the drier is running.
I've read a number of posts on this forum about the number of sockets one can have on a spur, and the answer seems to be only one, unless the spur is protected by a fuse box with a 13A fuse.
My question is, as the power spur is protected by a fuse in the consumer unit, do I still need the 13A fuse protection as well.
I think the answer is yes, if the fuse in the consumer unit greater that 13A,
but I would appreciate confirmation of this.
Also I know the regs about how much can be done DIY and what requires a qualified electrician have changed in recent years; as a DIYer can I add the fused spur box and the extra socket, or do I have to get someone qualified to do it for me.
Thanks in advance for your help.
Brian.

 

[EFLImpudence]

If the garage IS supplied by a spur then the 13A protection should be before ALL of the garage sockets AND lights; obviously limiting the total load to 13A.

There is no point having the CU in the garage.


Best find out for certain from where the supply is taken.

 

[PrenticeBoyofDerry]

You need to investigate further and confirm the configuration of the circuit, new socket outlets will require RCD protection, if this is not at the consumer unit protecting the new socket, then either fitting a RCBO at the board or a 13A RCD/FCU composite or Socket outlet with composite RCD.
If any cable is buried then this will also need RCD protection, so the first two options should be considered.

 

[oldbutnotdead]

Currently you can do the work yourself in that location with no requirement to notify Building Control but you must do the work to the required standard. Very handy guide to Part P on the Planning Portal http://www.planningportal.gov.uk/uploads/br/electrical_safety.pdf

RCD is always a good idea in a garage if the supply doesn't have one already

 

[PrenticeBoyofDerry]

RCD is always a good idea in a garage if the supply doesn't have one already

Not just a good idea, but with the introduction of any newly buried cable within the walls less than 50mm, without mechanical protection (metallic capping is not mechanical protection, something like metal conduit or ali tube cable would be) it is a requirement as it is for any newly installed socket outlet!

 

[oldbutnotdead]

RCD is always a good idea in a garage if the supply doesn't have one already

Not just a good idea, but with the introduction of any newly buried cable within the walls less than 50mm, without mechanical protection (metallic capping is not mechanical protection, something like metal conduit or ali tube cable would be) it is a requirement as it is for any newly installed socket outlet!

Indeed it is. If the OP's garage is anything like mine though he'll be clipping to the surface so the requirement won't apply there. But you're quite correct about the requirement for any new socket. Where's the 'hat off' icon when you need it? (I wouldn't dream of putting a new socket in a domestic environment without RCD protection- had to have a quick flick through the book to find the Requirement for it though)

 

[brianw3706]

Thanks for the responses guys; very useful.

 

[PrenticeBoyofDerry]

But you're quite correct about the requirement for any new socket. Where's the 'hat off' icon when you need it?

 

[AndyPRK]

Does the garage CU have an RCD in it?

Does it have a 16a MCB in it for sockets?

 

[PrenticeBoyofDerry]

Think I have already covered the RCD subject, although it has not yet been confirmed either way!

You need to investigate further and confirm the configuration of the circuit, new socket outlets will require RCD protection, if this is not at the consumer unit protecting the new socket, then either fitting a RCBO at the board or a 13A RCD/FCU composite or Socket outlet with composite RCD.

 

[AndyPRK]

I was just asking some simple questions to understand the situation

 

[ericmark]

When I was an apprentice a spur had fuse at destination and a radial had fuse at origin but that has all changed and we now have fused spur which I always called a radial and an un-fused spur.

With an un-fused spur the overload protection is at the destination so limited to one device only and 3 meters of cable this should not include the garage as you describe but people have been known to break the rules. Where the MCB or fuse does not match the cable size as for example a B32 MCB feeding a ring (2 x 2.5mm²) but a spur coming off that with single 2.5mm² cable the B32 MCB is too big for the cable so protection is from the 13A fuse in the final socket or FCU.

With a fused spur or radial the overload protection is at the origin it may be a FCU with 13A fuse or a MCB matched to cable size for example a B20 MCB or less feeding a 2.5mm² cable and as long as the volt drop limits and loop impedance limits are not exceeded you can add as many sockets as you like as any overload will take out the protection device at origin ensuring it fails safe. I would expect this to be the case with your garage.

There is now a requirement for RCD protection but using surface cable and a RCD socket this requirement would be met.

Where the problem arises is the appendix 15 where it states:- REGULATION 433.1.5 will be meet if (iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit. In the main a tumble drier is over 2 kW and over the weight for portable so classed as fixed, so should be on it's own dedicated radial circuit.

So with an item taking over 2 kW for an extended time you need to do a risk assessment. What is being looked at is the risk of this tripping the power and as a result not complying with one of the very basic regulations:- 314.1 Every installation shall be divided into circuits, as necessary, to:
(i) avoid hazards and minimize inconvenience in the event of a fault

The garage is supplied from the house by what I assume is a spur,

I hope you now realise this is the problem. Assuming is not good enough, you must find out how your garage is supplied which should be easy enough you only have to turn on lights in garage and then turn off breakers one at a time until you find which is feeding the garage and then find out what else it feeds.

Once you know this then return to this thread and say what you have found. Clearly assessing the risk is down to you but given the facts we can assist. Once you know MCB size and if it also feeds other items and also if there is any FCU then can start looking at the risk.

To this point I have assumed fed by 2.5mm² cable but as said should not assume. Using thicker cable it may be OK to feed multi-sockets from a 32A MCB. But to list all exceptions would take pages so best option is for you first to find as many facts as you can.

 

[PrenticeBoyofDerry]

Where the problem arises is the appendix 15 where it states:- REGULATION 433.1.5 will be meet if (iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit. In the main a tumble drier is over 2 kW and over the weight for portable so classed as fixed, so should be on it's own dedicated radial circuit.

But it is neither a cooker, oven or hob! And normally come with a factory fitted plug, so would assume the manufacture has done the calculations for the protective device !

Using thicker cable it may be OK to feed multi-sockets from a 32A MCB.

On a ring final circuit this would not comply to the requirements laid down by BS761. for a RFC and spurring from them.

 

[xr4x4]

With an un-fused spur the overload protection is at the destination so limited to one device only and 3 meters of cable this should not include the garage

Ok question...

If you need to run a spur off a ring final, to a fcu for example, if the 2.5 cable is longer than 3 meters the fcu needs to be at the beginning of the cable and not at the end?

Did I read that right?

 

[EFLImpudence]

If you need to run a spur off a ring final, to a fcu for example, if the 2.5 cable is longer than 3 meters the fcu needs to be at the beginning of the cable and not at the end?

Did I read that right?

Yes, but -

the FCU could still be within 3 metres but then I suppose the 2.5 wouldn't be more than 3 metres but two pieces.

Then again, if you put the FCU at the beginning it doesn't have to be 2.5mm²

Then again, again there's always 433.3.1(ii) but don't tell anyone without test equipment on a DIY forum.