Electric Supply to Garage/Workshop

[Terry W.]

Further to my previous post, which should be disregarded as I didn't know what I was talking about.

Please bear in mind that I know little about electrical supply and have only a vague idea about what a RCD does!

On my house consumer unit, the circuit for my garage is on the NON-RCD side. In my garage I have a white Fuse Box with a wire-type fuse. This box has only one fuse and an On/Off switch. The box is marked "45Amp" and the fuse has two yellow spots on it (if this is relevant). There is a cable coming off the fuse box to a row of 13Amp sockets above the bench and also to the lighting circuit

Question (at last): When using power tools etc. on my workbench, should I be using a plug-in RCD ?

My apologies for the basic nature of this question, but see second paragraph above.

Terry W.

[Jim Alexander]

The Prat P designers would have that on the RCD side but there is a better way.

avoiding answering a tricky question, I would fit something like this

A

[Sam Farrell]

I suppose strictly speaking you don't need RCCBs for your power tools but to be 100% safe I would.

First thing you could do is ask an elctriciaan to wire the garage to the other side of the RCCB in your consumer unit, but then a fault in the garage might trip the whole house so you would be none too popular especially if you were getting nuisance tripping from a faulty tool or device.

The easiest but possibly not the best option would be to use one of those things that looks like mains adaptor but has a built in RCCB . This could work out expensive if you have a lot of tools in use at the same time.

A better option would be to replace the socket or sockets in the garage with ones with in built RCCBs.

Both these options require little electrical knowledge but just make sure you switch of the power before you start changing sockets.

The ultimate answer would be to fit a box beside your consumer unit with an RCCB and fuse in it. The power to the garage would then be routed through it.

This is the sort of job that should really be done by an electricain or someone who really knows what they are doing so if your not sure don't try this.

Sam Farrell

[John Rumm]

It would only need to be on the RCD side (or better still its own dedicated RCD) if the house has TT earthing.

[David Hansen]

On Thu, 24 May 2007 13:01:12 GMT someone who may be "Terry W." wrote this:-

That's reasonable.

That is almost certainly the maximum rating for the unit.

That indicates that it is IIRC a 15A fuse [1]. I would check the wire is that size and would probably replace the wire to make sure.

It would be better if there was also a fused connection unit with a

3A or 5A fuse from which the lighting circuit was taken.

It would be a sensible precaution. In particular these things are a reasonable way of guarding against some forms of electrocution from cut flex.

[1] From memory 5A is white, 15A is yellow, 20A is blue, 30A is red and 45A is green. I pass on 10A, perhaps also yellow.

[John Rumm]

Can you work out what sort of earthing arrangement you have in the house?

sort of cable joins the house to the garage?

That rings a few alarm bells. The 45A fuse is probably way to higher rating to adequately protect either of those circuits by itself.

The short answer is yes.

[Jim Alexander]

Wasn't suggesting that or anything. Twas a jaundiced remark about the suggested part P diagram in the document which I think your good self posted the link to just a few days ago.

Jim A

[John Rumm]

Oh, you mean the example diagram in the Part P document. Yup I see what you mean. What they have shown is a bit naff although technically speaking correct given the lack of a local RCD in the garage/shed.

[John Rumm]

5A is white, 15A is blue, 20A is yellow, 30A is red. Never seen a 10 though.

[John Rumm]

Sorry ignore that (partly), Reading David's post about fuse colours I just realised you were talking about wylex style rewireable carriers:

yellow in this case would be a 20A carrier. Note however getting 20A wire to re-wire it with may prove difficult. (the 45A being the rating f the incomer or the CU itself by the sounds of it)

Ideally the lighting circuit ought to have its own fused connection unit though.

[David Hansen]

On Thu, 24 May 2007 16:21:39 +0100 someone who may be John Rumm wrote this:-

Blue and yellow are the two I usually have trouble remembering, which is why I look at the number stamped on the thing.

[John Rumm]

When I were a lad, there was no number stamped on ours ;-)

[David Hansen]

On Thu, 24 May 2007 17:53:21 +0100 someone who may be John Rumm wrote this:-

I'm too young to remember those days grandad:-)

[John Rumm]

Oi, cheek! The one I grew up with (which was waaaaay older then me ;-) had the dots, but no numbers.

[meow2222]

The short answer for the OP is it works ok as is, but there are some minor potential issues there. If you wanted to upgrade it all, the best thing would be to replace the outbuilding fusebox. That would

- put sockets and lights on different circuits, so a tool fault wouldnt kill the lights

- include RCD cover for all sockets

- probably increase the max power available from the sockets

- move lighting from 20A fuse to 5A or 6A, which would improve safety there a bit too.

However doing this is optional, if what you've got works ok and is in sensible condition its a bit dated, but not a disaster.

Re using plugin RCDs, you could but it would only address a small minority of the small issues. OTOH if your tools are such that theyre liable to cut through the mains leads, then yes good to use one.

NT

[David Hansen]

On 25 May 2007 04:54:12 -0700 someone who may be [e-mail] wrote this:-

It is often not cutting through the lead that is fatal, it is examining it without turning the electricity off. This was a particular problem with electric lawnmowers.