Workshop electric questions

[No skills]

Hello!

I'm going to have a good go at getting my single garage/workshop useable by xmas and have a few things to sort out including some electrical work.

I have one ring main for power and would like to add a separate 16 amp circuit to future proof myself against any new machines etc etc. Simply I want a 16 amp commando type outlet on the wall.

So question is how best to wire this up? A radial in 2.5mm t&e with a 16 amp type c mcb? The cable will be run behind a stud wall (2x2 timber with plasterboard and celotex in the gaps) in a 2" gap between that and the blockwork outer skin of the garage.

Do I need an isolator for the socket and wheres best placement for it - at the socket or fuseboard? What isolator is preferred or does it not matter?

Next... The feed to the garage (not installed by me) is armoured cable run under the house and out down the garden to the garage, just laying on the ground. This is fed from the consumer unit by a separate mcb.

I've had plenty of tripping in the house consumer from the garage in very wet weather, we took down a lean-to structure earlier in the year and found that the cable was badly damaged just after passing out from the house, I don't know if it was damaged on install or some big old rats had gone at it but it was down to the copper on all wires - it had been "repaired" with some black insulation tape :evil: :evil: . Luckly it was in a place that I could cut out the broken area and reconnect in an exterior box mounted on the wall, this solved a lot of tripping in wet weather but not all - so possibly more damage further down the line where the cable passes under the deck and plant boxes.

I want to pull up the cable and see whats going on, fix it to the wall that runs the length of the garden and repair or replace any damaged cable - is it worth running some sort of conduit down the wall and sticking the cable in that for added protection? or am I going too far I assume I should use a resin enclosed connection if there is another damaged section?

I have more questions but it would be nice to start here if you chaps can help

Cheers.

 

[n0legs]

Does the garage CU have an RCD?
Will you be fixing the cable to the 16a socket before or after the internal cladding/studding is done?

Depending on what useable lengths of swa you end up with it may be best to replace it. Good quality exterior grade boxes should be used with the cable correctly terminated in glands.

If I have to do a surface mounted termination outside, I use a quality box with a IP66/67 rating, gland the cable with exterior glands and then when I've made off the connections I fill the box with BICC insulating putty. It's non setting and exterior rated. Really pack it in there.
Cable joints exist for swa but should be buried. I've seen them left out of the earth but it's not the done thing if outside, on cable trays in a building it's a different matter.

SWA is tough enough for most situations, but route and other considerations should be made. If it's in a fairly sheltered position without too much potential for interference from third parties, then clipping it to the wall and burying it when it crosses the garden/path/drive/whatever is fine. Plan accordingly.

The isolator for the 16A socket, use a 20A DP switch with or without a neon, you choose, and I would prefer it near the socket. Better still buy a 16Amp outlet with an isolator fitted http://www.ebay.co.uk/itm/GEWISS-GW6600 ... 1992123462

 

[MMUK]

If you replace the SWA, you can use 5 core and use the spare pair for your commando socket, just use a common earth. I would mount an isolator directly to the commando, I'm fact you can buy these units ready built.

 

[No skills]

Quick reply as I'm at work - garage consumer unit is a household split effort, lighting on non rcd side and ring main on the rcd side (I have a question related to this but I'll wait till after work). House consumer unit is also a split, garage fed from an mcb on the rcd side.

The garage itself is partially lined out already, I've left gaps in the covering to run anything extra I wanted - now I know what I want I can get on. Any cable will run out the back of the consumer unit into the void behind the studwork and come back through the studwork/insulation into whatever fitting I fit.

Got to go, thanks for the reply - back later.

 

[No skills]

Right. I like the combined commando and isolator - I will be ordering something like that for my outlet.
I've not seen the insulating putty before so I will look into it. The box on the house is of the correct ip rating and I have used glands on it.
I think I will run some 40mm waste pipe along the wall to run the cable in, gives some extra protection and I could run any misc wires down it in the future (Internet??).

I'm not going to know the cable condition till the weekend (weather permitting), I'm hoping there's only one damaged section (yeah right).

 

[MMUK]

Personally I'd run data cables in a separate conduit to avoid any interference issues, preferably an earthed steel conduit.

One thing to be aware of. Your current consumer unit setup doesn't meet current regs so it's highly likely you'll have wiring of current and old colours so be extra careful when adding or altering.

 

[n0legs]

Here's a link to the putty:-
http://www.electricians-direct.co.uk/bu ... _14950.htm

Rather than use waste pipe to protect the cable, I have concerns over mistaken identity using it, maybe consider an exterior cable guard:-
https://www.tlc-direct.co.uk/Main_Index ... index.html

Have you got a megger/insulation resistance tester? A test would give you a clear view on the health of the cable. Combine with a good visual inspection and you can decide what to do.

Wiring in the 16A socket. You could go from the RCD side of the board with a 16A Type C breaker or from the non-protected side with a 16A RCBO. The Gewiss range is decent stuff and at the price in the link is very good value.

A point I make with regards to the condition of the SWA. If the cable has been damaged for a long time, water ingress could cause problems with the wire armour ie, it could have suffered corrosion. If this armour has been used to provide the earth/cpc, then this could be compromised. Test it's integrity with a continuity tester and find it's resistance if it is to provide the earth/cpc for the circuit.

 

[No skills]

MMUK and NoLegs, thanks!

I'll have a think about conduit, whatever I use will be mounted about 3' up off the ground rather than down at ground level.
The cable has a conductor being used as the circuit earth rather than the armour, I have made sure the armour is properly fitted in the glands in the junction box on the house. I don't know about the armour at the garage end though**, should the armour be in the earth bar in the fuse box?

**in fact I don't know about the house fuse box end either, gap in my knowledge here - should the armour be earthed at both ends or just one end or what

 

[n0legs]

, should the armour be in the earth bar in the fuse box

The armour should be bonded to earth at the source or origin of supply.
Use the supplied "banjo" in the gland kit and a short length of 10mm G&Y with a lug crimped on. Using a brass M5/M6 nut and bolt connect the lug to the banjo. Take the other end of the 10mm to the earth bar/terminal in the CU

If you have intermediate terminations in the cable run, use a banjo on each gland and connect one to the other with a short length of G&Y, terminated with lugs and secured to the banjo with nuts and bolts as above. No need to connect these, (I think the best way to describe these as armour continuity links, sounds about right) to the earth terminal of these intermediate connections/terminations. Just ensure for the full length of the swa the armour has continuity. Brass nuts and bolts please, no steel.

Keeping the cable up off the floor is a good idea, have you considered an overhead supply if you don't fancy the digging or are worried about the cable receiving further damage?
Use black waste pipe, try and avoid white. I know it's not likely you or anyone else will make the mistake and not remember/realise there's a cable inside, but black ducts are the colour of choice for electricity cables. Maybe a caution sticker here and there could be applied.
You may think "here he goes again" or "he's like an old woman" but I've seen some truly awful accidents as a result of no identification on apparatus , suffered a few close calls myself. I'll tell you about cutting a live 11Kv with a hacksaw one day.

 

[No skills]

Hello again.

I've had a dig round in the CU's and found that the cable armour isn't connected to earth at either end (doh!).
At the house end the cable comes up through the floorboards into the electric cupboard, the armour has been stripped back below the floorboards. Not a huge problem as I'm laying a new floor - but not till next year sometime

If I get access to the armour can I run it (in some earth sleeve) into some sort of enclosed connection box and then run an earth cable from that to the fuse board?

I'm ordering the commando and switch unit plus the mcb now, if the weathers rubbish this weekend at least I can make progress inside the garage (with a torch ). Need to get some brass nuts and bolts too, I used steel bolts in the banjo connections when I did the exterior box

Thanks for all the help, I do appreciate it. I'll try not to ask any more for a little while

 

[No skills]

Ah forgot..

Yes I will be using black waste pipe, can't really go over head as it leaves it open to interference from my dung for brains neighbour.

 

[n0legs]

Hello again.

I've had a dig round in the CU's and found that the cable armour isn't connected to earth at either end (doh!).
At the house end the cable comes up through the floorboards into the electric cupboard, the armour has been stripped back below the floorboards. Not a huge problem as I'm laying a new floor - but not till next year sometime

The best course of action would be to re-terminate the swa into a metal adaptable box.
The metal box will allow safe termination of the cable and the fitting of the necessary cable gland and earth provision. Fairly straightforward to do, then using a suitable sized T&E cable and a length of G&Y from the banjo as discussed earlier to terminate in the CU.
If you can't pull up enough of the cable above the floorboards to terminate properly bear in mind that any inaccessible junction boxes need to be of the maintenance free type. I'll leave you to decide if a junction/adaptable box below the floorboards is inaccessible.
Is obtaining a new length to run from the CU to the point outside, that you mentioned earlier, where you repaired the swa not an option?

Do not be tempted to use a BS951 earth clamp (earth clamps for fitting to pipework when cross bonding) around the swa to facilitate an earth connection
Do not be tempted to use a jubilee clip, as our street lighting cousins do, this will not be acceptable either.
If someone mentions the use of a constant force spring from one of the jointing kits these are designed for encasement inside the resin filled castings of the joint kits.
Also please whatever you decide to do, do not get the strands of armour twist them into a "pretend" conductor and try to crimp/connect/solder them to some G&Y and think this is the job done. Yes it may well work, but it is not the done thing.

Shame about the neighbours, some people could do with a little shock now and again.