Sparkies advice please

Apologies for the long post, but details never hurt. Here goes...

For a while now my workshop (side garage) has been dark and under powered with one lonely light bulb and one mains spur from the house going to a double socket and quite a few multiplugs - I have never been too worried about overloading the spur as I am only ever running one machine at a time.

However I would like to install a Ring Main so that I have plenty of socket outlets available around the workshop and I wouldn't have to keep on dragging an extension round or swapping out various tools for the other. I would also like to install some descent florescent lighting.

Last year I got an electrician to come have a look and give a informal quote. Due to the consumer unit being on the opposite side of the house he wanted to rip up half the house's floorboards (a snowball's chance in hell if SWMBO has anything to do with it) and have to completely empty the garage to do the installation (understandable but something I am loathed to do nor have the resources for). He very much had a "my way or the highway" attitude; which all in all meant nothing has progressed.

My intention is to get a qualified electrician to run a circuit on the outside of the house, either from the consumer unit or the service cable to a small 4way fuse box inside the garage with a couple of 30A MCB with RCD protection. I would then install the ring main myself and yes I am aware that this work will need to be notified and certified - leading onto my questions:

- Conduit and socket outlet type - The existing are all protected in metal conduit (although only up to the beams where the flex is secured to the wood) and have metal cases. Except the outside light switch which is plastic! Would it be sensible to follow suit with this or would plastic cases with clipped wall mounted T+E be acceptable?

I believe the regs say "All wiring systems and equipment have to be suitable for their intended location and use taking into account all extraneous influences" Although personally I struggle to see what one would be doing in the workshop to end up splitting a wire on the wall or smashing an outlet but there you go

- Lighting - Can I modify the existing lighting spur circuit to incorporate three florescent tube units? Do I need to be conscious of the power ratings and would it be advisable to use energy efficient lighting to keep the rating down? If not I will ask for a 6A MCB in the fuse box and wire the lighting from here.

If you've managed it this far then I owe you already and if you are able to constructively comment constructively then I would be indebted!

I'm sure there are many other points which I have forgotten but this is plenty for now.

Many thanks

I would be inclined to run the supply from the existing CU using SWA cable buried in the ground (700mm ish down) This would the feed another CU say 8 way, more is always useful, I would then run all power and lighting circuits from this CU. As far as power rating go main cable feed 6mm2 min even if you do not use all the capacity at least if it is big enough then if you need a dedicated supply for say a welding set it all ready to go.

This not so dissimilar to what I have but ran 10mm twin and earth from the main CU through the loft space (bungalow) into the attached garage, friendly sparky who is willing to just do the connections, test and sign it off.

Bob

Hi Tom, You say the socket is on a spur from the house, that usually means that there is only one cable at the socket. If however there are two cables at the socket, you can split these and add another couple of sockets (extending the ring). Modern flourescent lights with electronic ballasts are very efficient, and would place a low demand on the existing system, so you could fit them to the existing wiring . To give you some idea of loading my shop has eight (1970's) 8ft flourescents (one an ancient twin tube model) and two 6ft, putting the whole lot on at once draws about 7.5 amps, and will blow the five amp fuse in about tweny minutes, so with modern fittings you are nowhere near overloading. The submain is a good idea, but you are in a grey area in that the electrician who does this work will have to be "part P" registered, and is put in a difficult position if he just wires the submain, and leaves the rest to you. Not that there is anything wrong with doing that, but most of them only have a passing understanding of the part P scheme, which is an impenatrable mess of seemingly conflicting cans and cants and will tend to fly well clear of anything they think might cause problems down the line. Might be best to let him do it all. For sockets I have used twin 13A metalclads, with plastic conduit drops which go into the ceiling and 2.5mm twin and earth cable as normal. Doing a metal conduit job is prohibitively expensive, and tends to be used only in extreme commercial environs, and wiring conduit in singles is also far more than you need to do. You are not wiring a factory, just a home workshop

Phil

May be quicker, cheaper lifting a few floor boards rather than digging round perimeter or even cable fed through conduit.

Luckily was in same scenario 24 years ago but old fuse box by garage doors with very few outputs and single light bulb. Back then could do your own without passing off. Specific feeds for certain machines wired in and 9 double plastic surface sockets on 4 spurs. 4 off 5ft fluorescents, 4 way switch off separate house feed, it happened regularly tripping the split load at least have lighting. Ok by pro sparky at Longbridge then but not passed off.

Annoyingly electric co lowered the outside feed fuse to 65A from 100A, hob draws 32A, inverter can draw 35A, shower 45A, luckily can manually throw the MCB when having a session so others cant use.

Not sure on current legislation as far as I am concerned new fuse box put in 2003 was done before along with the workshop lights and fittings not using the current spec cable. Far easier to get sparky to wire in new fuse box to workshop by whichever method and do a better job yourself putting the sockets exactly where needed if can still do. Mine uses plastic rectangular conduit, 1 1/2" for the 32A feed using the old 40A shower cable put in 4 1/2 years ago with extra 32A C MCB. Inevitably sparky would position sockets etc too high or in wrong place, drawers and units built around the machines.

Thanks for the advice guys.

Bob - no chance of burying as garage is infront of tarmacced drive. You mentioned a welder - I have a Sealey 150A MIG, which of course doesn't reach anywhere near 150A in reality, it has been used to good effect on the existing circuit though I suspect not to full power due to cable losses. Nothing has tripped anyway. Would you say it was sensible to have a dedicated curcuit specifically for the welder? I was considering this.

Phil - it's a double socket but I think only a single T+E flex, will check when I get back home after the weekend. If it is part of an existing ring that would've blooming marvellous. Thanks also for the clarification on the lighting.

Jon - my house was built on what would appear to be a very small budget and has a few quirks when it comes to things like this. I fear if I try to lift the cheapo chipboard floors I'll have to replace them. But otherwise yes what you say makes sense.

Thomas,

If there is no chance of burying the cable then using SWA cable clipped with the proper clips to the wall at a height where the chances of it getting damaged are minimal.

As far as the welder is concerned I would put it on it's own dedicated supply, it looks like the power consumed flat out is around 4.5Kw or 19amps. I have a dedicated 32amp industrial switched outlet installed for exactly this purpose.

Bob

Hi Thomas.

If it's outside the cable has to be protected. SWA (Steel Wire Armoured) or in steel conduit. SWA is much easier to handle.
The way to do this easily and economically.
Use 2.5 mm 3 core SWA on it's own 16 or 22 amp trip (not more than 22 amps) from your house fuse board. Don't connect the Steel armour to the House Earth. Just the Earth wire.
If the run is 50 meters or more it may be worth going up to 4mm. Especially if you want to run a welder.

*** If you have Wire fuses it really is time to replace the entire fuse board in your house. Not a DIY Job ***

Connect to the NON RCD side of an RCD'd fuse board in the house. If you want an RCD on the House side as well, use a 100ma RCD not a 30ma.
If your workshop RCD goes at night you can find that. Finding your way back to the house (which may also be in darkness with an unhappy SWMBO) is not so easy.

In your Workshop connect your SWA to a 30ma RCD'd Fuse Board.

Use a 5 amp trip for Lights. You can run 500w off that (5 long tubes)

Use 1.5mm Twin and earth to build your ring main. Attach that to a 16 Amp (Not more than 16a) trip.
You have the option of a 16A /30ma RCDBO (trip and rcd combined) and 5 amp trip for lights if you wish. That means the lights should stay on if the trip goes.

The last and vital thing. Get an Earth Rod. Attach the Earth from the workshop AND the Steel Armour from the SWA to the earth rod with 6mm Earth Cable. The rod must be knocked home in Soil. You can bury it if you desire.

Alex

Hi Thomas

I'm part P

If I was you I would put in a dedicated board for your workshop. Run a 10mm SWA from your existing board or 25mm from a henly block depending on the load. You don't need to pull up your chipboard floors. you can cut some holes in strategic places and pull the cable through with a cable quick or a fish.

use surface mounted acc's with cables mounted in plastic round conduit easy to install and alter if need be in the future

remember use an RCD or RCBO's

regards

Paul

OOp's

surface mounted acc's should be metal clad for best protection

regards

Paul

I think even 4 mm SWA is too small I would use 6mm as a minimum ok it is more expensive but no point in using the minimal size do it once.

Didn't know you could get 5 amp breaker, 6 amp is more like it, most ring mains have a 32 amp breaker although 2.5mm cable is only rated at 24 amps any socket is fed from two ends.

My workshop has 8 5ft twin LED T8 fittings total load 160 watts

Bob

Edited By Bob Brown 1 on 22/05/2015 23:14:10

Hi Thomas,

You are getting a lot of advice all based on assumptions of the electrical characteristics of your supply, and of your knowledge of installing electrical circuits, and how you interpret the advise given. Two cables at a socket do not guarantee a ring it could be a double spur or a radial circuit. Just because you have wire fuses, ( BS3036 semi-enclosed fuses ) does not mean you have to replace the fuseboard, it depends on its condition and the condition of other things as well. An earth rod is a very vague description of what is required for Earthing an Electrical Installation, it and its connecting cable, and its resistance to earth must comply with British Standards, (BS 7671: 2008 (Seventeenth Edition) 3rd Amendment - 2015) to be safe. The best way is to get a Qualified Electrician to check what you have now and advise you on how to install what you require, and to check and Test it it when complete.

Regards,

Brian.

Assuming its a conventional ring main,why not find where the spur joins into the ring,and just extend the ring from that point. Or a cheapy solution ,currently you state that the socket meets your power needs its just the tangle of the extention leads that is your problem,so put some sockets around the garage where you need them and have a length of flexi cable from the last socket with a thirteen amp plug to the existing fixed socket in the garage,all this has done is in effect is made the extension leads a bit more permanent,the advantage is the garage circuit can be isolated by a pulling the plug,if this is done every time it reduces the risk of leaving an appliance "ON" ie a soldering iron, I dont think it illegal,though if you moved house its a simple job to remove the temporary sockets.The new regulations are there I suppose to protect people from DIY bodge jobs by the current generation who cannot even change light bulb,or if they do they need a hard hat,goggles, and hi vis jacket.But there are a lot of sparks who are not that clever,after the 1987 hurricane, my neighbour had a sparks from one of the building sites he was involved in,fit a generator change over switch , and asked did I want one fitted,cash in hand . a long time afterwards I fitted a new consumer unit and then found that the heavy leads from the c/o switch were undersize, correct size leads could be fitted but he was too idle to struggle with the heavier leads.so much for proffessionals.

If you stuck 99 Sparkies in a room and asked them to specify a job you'd get 100 different answers. Some of them would also be fighting about it within half an hour.

THOMAS ... there are many ways you could finally end up rewiring the workshop ... difficult to tell from a long distance ... keep it as simple as possible ... as well as fluorescents, look in the supermarkets for LED lamps ... a bit pricey but some of them supposed to last 20 years ... some look like chunky light bulbs but they are remarkably bright ... some look like 12 volt halogen spotlamps and are a direct replacement .. some even work on 12 volts DC as well as 12 volts AC ... the ones I have recently fitted in the workshop are made by OSRAM or TESCO`s own make.

JON ... you talk about the electricity board lowering your supply from 100 amps down to 65 amps ... did they talk about installing a meter that registers KVA instead of KW ... in other words an industrial installation rather than a domestic one ... a lot of old fluorescents and induction type mains motors have no power factor correction capacitors ... lots of current, but out of phase ... were they worried about all the lights going dim when you switched anything on ??

Thomas

I had, or have, the same problem. My garage, attached to the house, had one socket and two lights fed off the house ring main through a spur. When I had the garage enlarged to include my workshop I put in a ring main and lighting, low powered general fluorescent lights, circuit. This I did using the Workshop Practice Series No.22 book as a guide. I ran both circuits to a consumer unit fitted with circuit breakers. This was fed from the spur, just retaining the one socket and 13 amp fuse plug (I had removed the two original lights). My intention was to find someone mug enough to hot wire the consumer unit to the house consumer unit but no one I knew was willing to do it.

Then the regulations concerning electricians etc came in to force so I just left it as it was (and is). As far as I am concerned my circuits are fed through a standard 13 amp fuse which should protect the house circuit and if the garage/workshop electrics give problems when selling the house they can be ripped out in a few hours.

For record I have never blown the 13 amp fuse and the maximum load has frequently been something like 6 30 Watt strip lights, an oil filled convective radiator, radio, 3 25 Watt low voltage lights and a Myford Super 7 with DRO and coolant pump. That is about 6 amps steady running rising to about 9 for a short time when starting the lathe.

A final comment, I put 8 double sockets in the ring main and that was not enough.

JA

Here's a link to a useful cable size calculator **LINK**

Probably about 10 yrs ago now Martin, electric supplier organised a new KVA meter outside which was fitted. Week later no notification some one came round broke the tag removed 100A fuse and installed a 65A fuse.

Vented my anger stating hob alone draws 32A, shower 45A without anything else. Didn't say ran machinery at time lathe and compressor drawed back then 26A. Harrison lathe back then used to blow 13A fuses 1 in 5 startups bought in 100's which baffled the sparky.

Re. " If you ask 99 Sparkies...." Perhaps it's time time to ask an electrical engineer! After all would would you ask an Auto Technician to design a gearbox? (no disregards to Auto Technicians) Its a question of the right person for the right job! I have seen with my own eyes examples of alterations to electrical systems that could have caused death or damage by fire over the years.

Need I say more?

John

Edited By Johnboy25 on 24/05/2015 07:31:49

Vic and Johnboy25,

Electrician's who have been to college and passed exams are quite capable of designing and installing electrical installations! You may have seen some dangerous installations but do you actually know who installed them and what background and qualifications (or lack of) they have? Were they really Electricians?

You seem to be making certain assertions about all Electrician's with your comments. As in engineering there is more than one way to skin a cat and you're bound to get differences of opinion from different "Sparkies" as to how to tackle a job.

Ed.

Edited By Ed Duffner on 24/05/2015 12:42:23

Ed...

On the contrary Re. "I seem to be making certain assertions about all Electricians..." I totally agree that there are Electrians that should be more than capable of designing safe electrical installations and I am not slagging off my profession. As an practicing electronics and electrical engingineer and being affiliated with the IEE now the IET, I feel adequately qualified to pass comment as opposed to some people with ideas of what is safe and exceptable. Since the introduction of Part P, which I may say I was was opposed to on the grounds the someone was making money enforcing these regulations. (But that another discussion in itself and has been raised on numerous times) there has been a reduction of dodgy installations installed by people with little experience or knowledge regarding what's acceptable. 

So I'm sorry if I hit a nerve with my reply to a previous posting. I've come from hands on from the tools as it were. So I've been there, seen it, designed it or repaired it!

John

Edited By Johnboy25 on 24/05/2015 13:02:33