sanity check - adding sockets to garage

[adlad84]

Hi
I'm looking to add a couple of sockets to a garage which will be used as an occasional study area / workshop. Just want to hear opinions over the proposed design and if it will be ok?

The garage is protected by an rcd and connects to a 32A mcb in the main cu in the house. There is a 10mm twin + 4mm earth cable that goes from the cu in the house (buried underground to separate garage) to an old style wylex fuse box with replaceable wire fuses. The cable looks new (however i have a feeling the advice will be to replace the fuse box?).

The new wiring i would like to put in, 1 circuit (with 30 amp fuse on the garage fb) will feed a computer, monitors, and an 1500W radiator. 2.5mm T+E will be dropped down from ceiling to sockets in a stud wall with insulation, with the cable pinned to the stud.

The wiring with 16 amp fuse will just feed a kettle and possibly the odd power tool, again behind plasterboard and insulation and dropped down from ceiling height.

Currently, each socket is in radial fashion from the fb with x2 2.5mm T+E cables. Since there are x2 cables I thought adding in sockets and retaining to x2 2.5mm T+E cables into the FB will keep it as close as possible to current design without the need for a sparky to replace the FB?

Hope to hear opinions, whether good or bad? Many thanks

 

[EFLImpudence]

There isn't much point having two 30A fuses (nor a separate 15A one really).
You may as well connect all your sockets to one.

Use 4mm² T&E and connect the sockets in whichever configuration suits the locations.

 

[adlad84]

thanks. If i said i'd already 1st fixed some of the 2.5mm T+E (i know i've done things back to front) will the proposed design be ok?

 

[EFLImpudence]

thanks. If i said i'd already 1st fixed some of the 2.5mm T+E (i know i've done things back to front) will the proposed design be ok?

Yes.

 

[winston1]

You don’t need a ring on the 16amp circuit. Just wire it as a radial.

 

[winston1]

Looking at this again your two 30 amp fuses are a waste of time. Whether on overload or fault the 32 amp house MCB will trip before the local 30 amp fuse ruptures. MCBs are much faster. Just get rid of the local fuse box and connect all the sockets on one ring starting and ending where the SWA enters. This is known as a lollipop circuit. Run your lights from a switched FCU with a 5 amp fuse from the same ring. The switch can double as your light switch.

 

[SUNRAY]

Looking at this again your two 30 amp fuses are a waste of time. Whether on overload or fault the 32 amp house MCB will trip before the local 30 amp fuse ruptures. MCBs are much faster. Just get rid of the local fuse box and connect all the sockets on one ring starting and ending where the SWA enters. This is known as a lollipop circuit. Run your lights from a switched FCU with a 5 amp fuse from the same ring. The switch can double as your light switch.

I think I've confused this with another thread as I thought something like this had been suggested. As winston says the 30A fuses will take longer than the 32A MCB to trip, the same is potentially true for the 15A fuse too.
If you wish to retain additional protection in the garage you will do better to replace the fuses with MCB's of no more than 16A or 20A rating ideally.

 

[securespark]

Still not convinced there will be discrimination.

A 32A radial circuit feeding sockets, with spurs fused down for lighting?

 

[adlad84]

See what you mean about the fuses. So if I decide to do that (with the ring breaking off the swa instead of having a fuse box) can you advise what kind of junction box I'd need?

 

[SUNRAY]

See what you mean about the fuses. So if I decide to do that (with the ring breaking off the swa instead of having a fuse box) can you advise what kind of junction box I'd need?

Let's start again with this.The fusebox you have at the moment is OK (assuming it's not faulty), you can continue using it and connecting your new sockets as discussed without problems. However as we've now said the 30A and possibly 15A fuse are unlikely to blow but a smaller fuse such as 5A is required for the smaller cable of the lighting circuit.
Moving on to recent suggestions the fusebox can be removed and a fused connexion unit can serve as lighting fuse and switch.

But you don't have to remove the fusebox. If I were doing this, personally I would install an isolator switch such as

Or

and a suitable deep backbox.
Either of these would be suitable and serve as the origin of the ring circuit.
As said the existing fusebox is fine to leave in place, unless you'd prefer to remove it.

One idea for a junction box

https://www.tlc-direct.co.uk/Produc...PCZa3HqZTb8c_lqeQvndVZJlf7RC29u0aAnCIEALw_wcB

 

[adlad84]

Thanks Sunray. I am leaning towards keeping the fuse box as I'd prefer to keep the work non notifiable and if I'm starting to touch fuse boxes I'd probably need to get a spark involved.

I was considering swapping the 30A fuse with this:
https://www.screwfix.com/p/wylex-16a-sp-type-b-mcb/34544
And running the new sockets off that. And a 5A mcb for the lighting circuit.

Agree that it would be best to do the above but as long as it's all safe and I'm staying in what's allowed for diy-er?

 

[EFLImpudence]

Yes.