Workshop Consumer Unit

[eeyore2]

I want to put a ring of sockets and some lights in my outdoor workshop, which is attached to an existing home office that has it's own RCD protected consumer unit with some "available" 32A mcbs.

Assuming I go with a 2 way CU in the workshop, do I connect this into one of the spare mcbs or direct to the RCD in the office CU?

If I go from the 32A mcb in the office, can I then have another 32A mcb in the workshop for sockets, plus a 6A for the lighting circuit or do they need to total less than the 32A "feed"?

Sorry if it's a basic/dumb question but I would appreciate some advice

Thanks.

 

[ricicle]

http://www.competentperson.co.uk/

 

[rebuke]

Firstly, note that this work would be notifiable to your LABC under Part P before carrying it out...

What appliances are you intending to use in the workshop, as you have to look at actual intended usage, not just what the breakers are rated to (i.e. you work out the load, then work out what breakers would be appropriate, not assume the breakers then work out what load can be used).

I'm a little confused by what you say about the CU in the home office though, where is this fed from - is it fed directly from the incoming supply (through a meter of course), or is it fed from another CU, in which case what is the rating of the breaker supplying it. Some pictures would be useful...

In general, you should not take the feed directly from the RCD, as you almost certainly wouldn't have appropriate overcurrent protection. If the home office CU is fed directly from the incoming supply, then the only circumstance this could possibly be acceptable would be if there was a device upstream of it with an appropriate rating (e.g. if the RCD was rated to 80A, and the cut-out fuse was 80A). Even then, I'm not sure if that would be within regs, and it definitely wouldn't be best practice, and you'd need to use some pretty thick cable!

If the office CU is fed from a breaker in the main house CU, then you could potentially just split the supply going in to the office CU to the one in your workshop, and put an RCD main switch in the workshop as well. It might be useful if you upload some pictures of the CU(s) etc...

 

[eeyore2]

Thanks for the reply rebuke. To answer your questions:

The office CU is fed from a 32A mcb in the non RCD side of the main house CU. The sockets in the workshop will be used for DIY powertools only.

Assuming I feed the workshop CU from the RCD protected side of the office CU do I really need another RCD in the workshop?

Am I OK with the 32A and 6A mcbs in the workshop or do I need a smaller mcb for the sockets (16A?).

 

[rebuke]

You don't need a second RCD if one is already present (unless it's a 100mA one rather than a 30mA one, but that's unlikely) - it's pointless as any fault would take out both, not just the most immediate one.

If the office CU is limited to 32A, then installing an additional 32A ring is bad practice, if it were me I'd just put in a 16A radial in the workshop. Note however, that some power tools can be quite high power usage, so depending on the size of your workshop, it may not be sufficient to put in a 16A radial, at which point you would basically need to put a separate feed in from the house CU.

What cable etc are you planning on using between the office CU and the workshop one?

 

[eeyore2]

Thanks. The RCD in the office is 30MA so I guess that's covered. There's a spare 16A mcb in the office CU too so I can take that and use it in the workshop as you suggest.

My power tools are only "normal" DIY stuff so shouldn't cause a problem.

The cable from the office CU to the workshop CU is 6mm armoured. OK in your opinion?