DIY - Detached garage

[Pirate1Steve]

DIY ADVICE / POST

Hi All,

It's my first post on this forum, I hope I'm posting correctly, finding the guidance of where to post a little confusing!

Intro
Just after some advice on my current set up and whether I can and can't do this without getting a sparks in. For reference, I'm happy undertaking any electrical work I'm allowed too, and would like to think I'm competent in that respect (have added spurred sockets in the main house, repaired broken cables and had them tested by a sparks etc). Anyway, will try and be concise.

Situation
Detached garage circa 35m from house. Dedicated 2 way Wylex fuse board in house (grey box shown bottom of picture). This has one 30 amp rewireable fuse that feeds the garage. Other end of cable (in garage) has another 2 way fuse board (same unit as in house). This has one 5 amp rewireable fuse and one 20 amp rewireable fuse.

Problem
The 20 amp fuse is used for a radial on 2.5mm T+E and pulls close to 20 amps (4.5kW of heaters & other equipment). I want to increase this to 23 amps (5.5kW of load), but this can be on 2 separate radials as I ideally don't want to upgrade the radial to 4mm.

Questions
1 . Would there be a safety reason that the garage supply cable has a 30amp fuse one end, and 25 amps the other? I'm presuming that they were installed this way so that 1, the garage would trip first for convenience or 2, because the original owner wanted two circuits in the garage and you can't get two fuses that add up to 30amps.
2. Is it absolutely necessary to replace the old Wylex unit in the main house, that feeds the garage, considering this works fine and would have been compliant when installed. Note - I know I would definitely need an electrician to do this.
3. My plan is to replace the old Wylex unit in the garage with a new consumer unit with 3 MCBs, 1 6amp for the lighting and 2 16amp for the radials. Is this reasonable?
4. Understand that adding a new circuit is notifiable but would this be classed as a new circuit as I am in essence altering the existing?

Thank you for any help / advice

 

[mainline]

DIY ADVICE / POST

Hi All,



Situation
Detached garage circa 35m from house. Dedicated 2 way Wylex fuse board in house (grey box shown bottom of picture). This has one 30 amp rewireable fuse that feeds the garage. Other end of cable (in garage) has another 2 way fuse board (same unit as in house). This has one 5 amp rewireable fuse and one 20 amp rewireable fuse.

Problem
2 separate radials as I ideally don't want to upgrade the radial to 4mm.

Why go to the trouble of adding another cable, which I assume would follow the same route as the other ?.
Why not upgrade it.

Questions
1 . Would there be a safety reason that the garage supply cable has a 30amp fuse one end, and 25 amps the other? I'm presuming that they were installed this way so that 1, the garage would trip first for convenience or 2, because the original owner wanted two circuits in the garage and you can't get two fuses that add up to 30amps.

It was to try to get some selectivity.

2. Is it absolutely necessary to replace the old Wylex unit in the main house, that feeds the garage, considering this works fine and would have been compliant when installed. Note - I know I would definitely need an electrician to do this.

What type of cable is supplying the garage and what route ?

3. My plan is to replace the old Wylex unit in the garage with a new consumer unit with 3 MCBs, 1 6amp for the lighting and 2 16amp for the radials. Is this reasonable?

It's going to depend on a number of factors, but I would say no at least to the use of mcbs.

4. Understand that adding a new circuit is notifiable but would this be classed as a new circuit as I am in essence altering the existing?

Whether the work is notifiable or not, it still has to meet requirements.

I don't think anyone is going to yes it's fine, as in reality it's not.

My first thought would be:

Does it meet the requirements for disconnection.
Are the earthing/bonding requirements satisfied.

Advice is, get a competent electrician to give you a quote.