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What should I budget for getting a workshop wired up?

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JoeT09/10/2014 23:28:59
24 forum posts

Hi guys - obviously I am going to need to get some quotes from some electricians, but very roughly, what sort of budget would you think I'm going to need to get a new consumer unit with RCCB's and a few high current sockets (16/25A) in an internal garage?

I'd really like a welder and a higher HP single phase machine tool or two, so I don't think the existing 13A sockets will cut it.

Cheers,

Joe.

OuBallie10/10/2014 15:57:49
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1156 forum posts
661 photos

JoeT,

Far far to many variables for anyone here to suggest or even hazard a guess.

I certainly would not.

Only an electrician will be able to give you a price.

do sit down when he does though or

Geoff - Is only me or do others find single core cabe a real REAL PITA?

Spurry10/10/2014 16:15:02
219 forum posts
72 photos

I would much sooner poke three cores of single down a conduit with bends, than try the same with T+E.

YMMV

Pete

Ed Duffner10/10/2014 19:04:16
832 forum posts
94 photos

Hi Joe,

For a small home workshop, my preference would be to install a trunking system around the perimeter with a basic ring circuit and capacity to add more circuits in the future if required. Doing it this way you could install basic power distribution in your workshop and decide later if you need to add or move socket outlets. Individual circuits can also be installed for the higher current requirements e.g. welders and so on. It's always handy to have standard 13amp socket outlets for power tools, vacuums etc.

Some things to consider are sockets, lighting and heating, type of circuit protection (I'm not sure how welders cope with RCCB's but in my Brother's workshop the welder kit sometimes trips an mcb on the dis' board).

You already have an idea of what you might need so as Geoff says have a chat with an electrician and he/she should be able to quote on whatever you decide to have.

One thing I thought about the other day, with the nights drawing in was to have a secondary light on a seperate circuit, even if it's just a machine lamp plugged into a socket. If you only have one lighting circuit and that trips out when you have machinery running... ...I'm sure you get the idea.

Ed.

Robin Graham10/10/2014 20:52:43
904 forum posts
277 photos

Hi Joe, it is a bit 'how long is a piece of string', but if it helps my recent experience was about 350 for supply / installation of a new consumer unit supplying the house, two 32A circuits for 13A sockets in the workshop, two lighting circuits in the workshop (recommended by sparks for exactly the reason Ed gives above) and a dedicated 32A circuit for a welder or whatever. The whole job came in at a tad under 1k which included supply and installation of 10 13A double sockets, 5 twin tube fluorescents, a floodlight for the yard and the dedicated 32A socket. Took 2.5 days for one chap. It can be done cheaper if you do the wiring yourself then get an electrician to put in the consumer unit, connect up your work, test it and sign it off. Not all will do that though.

Robin

Chris Denton10/10/2014 22:38:23
275 forum posts

I'd agree with the trunking, but with conduit coming from it to metal clad sockets. It's easy to fit and very easy to change or add new sockets etc. Use Thermosetting Single cables (IMHO), T&E is terrible stuff. Use double the trunking size you actually need to allow for changes etc.

The most important thing of course is the size and type of supply cable that is leading to your workshop as that will determine what you can use.

Flourescent tubes are good but if they are near head height then they can make your head feel hot!

RCD protection on everything, personally if you only have a few circuits then I'd use an RCBO on each circuit.

 

I'd agree that most electricians won't give you a certificate if they haven't done the work. But in this case all the cables will be visible and can be easily traced.

 

Screwfix are cheap / good for electrical stuff. A lot of the electrical suppliers won't give you a good price if they think your bit an electrician.

 

Edited By Chris Denton on 10/10/2014 22:39:38

Steve Sharman10/10/2014 23:39:54
25 forum posts

Geof is quite correct when he says too many variables to even suggest a ball-park figure. I would also suggest you consider the following.

Primary supply - contrary to one of the suggestions above, the starting point must be what your maximum demand will be, not what your existing cable will handle. It's no good deciding to throw in a length of 2.5mm T&E and expecting it to supply all your needs.

How far from the house consumer unit is your workshop (cable run, not "as the crow flies"? How much current will you require under the most onerous conditions? How is that cable going to be routed if your workshop is remote from the house - surface, overhead, buried? What means of earthing are you going to use - earth rod, suppliers earth? Do you understand the risk of using a suppliers PME system (TNC-S) earth in a remote building (sometimes called exporting the earth) and the differing potentials that may occur between the suppliers earth and true earth? How are you going to protect your submain - steel wire armoured, RCD at the front end? Can your service fuse handle peak demand? (It probably can but if you have two daughters both spending twenty minutes in their respective electric showers while your wife is cooking breakfast and you start welding, a 60A service fuse might decide to say sod it!)

If any of these points make you think "what the heck is he talking about" then I strongly suggest you get an electrician to discuss this with you. He will know how to calculate the cable size and type to best serve your needs and, more importantly, how it will affect the overall supply to your premises. And this is all before you start wiring the workshop.

Steve

Where did that stupid smiley come from????

Edited By Steve Sharman on 10/10/2014 23:40:52

"Bill Hancox"11/10/2014 00:16:28
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257 forum posts
77 photos

Joe

Buy the horse first Joe, then buy the saddle to fit the horse. You need a plan. Make a decision about what you want for machines and where you want them located in your shop. Determine the power requirements of all machinery and devices such as air conditioner. Bear in mind that you should only have one machine or tool operating at a time. Compile a dimensional sketch of the shop layout that you have in mind marking out the machinery, receptacle and switch locations, light fixtures etc. Consult with a knowledgeable electrician to establish your requirement.

Cheers and Good Luck

Bill

JoeT11/10/2014 08:53:40
24 forum posts

Thanks for all the replies guys - and sorry for giving so little info in the first post!

We have just moved into a 1960's house with an extension built in 2000's that contains the attached garage I plan to use as a workshop for spannering and machining, though probably not both as once!

The garage is about 1.5m away from the existing CU, which doesn't seem to have any spare circuits. The CU's main breaker is 83A but there seems to be some 1960's breaker rated at 60A between it and modern digital meter. I really need to get a sparky in to tell me how much power I can really pull at once, and whether or not that 60A antique can/should be uprated to meet more modern standards. There are currently 2 40A breakers in the CU for the 2 power showers, I may have to negotiate with the mrs about hijacking one of those! Everything in the existing CU seems to be on 2 RCCB's - one for lighting and one for everything else.

The garage already has 4 13A sockets, on a circuit shared with the rest of the extension. I would really like to get these and any other sockets in the garage wired into a new CU in the garage itself so that I can isolate things from within the garage.

I agree with the suggestions of putting in another ring with room for expansion - I'm hoping I can find a sparky who will at least let me run all the trunking and position all the outlets myself, even if he/she will do all the actuall wiring. I would like to run individual feeds from the new CU in the garage to each of the high power circuits.

I don't plan to be welding while using my lathe, but I do plan to CNC all the machine tools, so I do expect them to be drawing upto 13A each and a couple to be running at once - I will probably need cooling rather than heating!

I am also a big fan of not being electrocuted, so I plan to have RCCB's on every circuit in the garage - I'd like to be able to trip something in there without tripping the main house RCCB if possible.

Anyway, I guess I need to find a few decent sparkys and get a few quotes.

Cheers,

Joe.

Swarf, Mostly!11/10/2014 11:03:36
621 forum posts
66 photos

Hi there, all,

It seems nowadays to be commonly thought that the more RCDs and/or RCBOs you throw into an electrical installation, the safer you will be.

You might be safer from electrocution but you could easily die of frustration! My point is that nobody (except the IEE Regs, sorry, BS7671) ever seems to mention discrimination.

It's important that, if you get a fault, the protective device that trips should be the one closest to the fault. The installation design should avoid/minimise nuisance tripping that takes out good circuits along with the faulty one.

If the structure of your wiring 'tree' has several RCDs and/or RCBOs in cascade, all of the same fault current & trip time rating, it's unpredictable which one will trip first. Read the catalogues of the popular suppliers and see how often/rarely there is any mention of those parameters!

While I'm at it, I'll chuck in this one too - if all your domestic installation is 'protected' by a single main RCD and, while you're on holiday, a spider commits hari kiri in some remote junction box, you're going to experience an awful pong when you return home and open the freezer door! IMHO there are some appliances whose character and situation are such that RCD 'protection' is OTT - a sound CPC should be enough!

Best regards,

Swarf, Mostly!

Bob Brown 111/10/2014 12:13:52
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1021 forum posts
127 photos

The main fuse on the incoming supply should give you an idea of how much power you can pull off the supply, I would be surprised if you could actually pull the full load if the main fuse is old. The CU breaker current does not have any bearing on how much power you can pull, the rating on them is only an indication of what load they are rated for. It is not unusual to see a 100 amp main breaker in the CU but only a 60 amp main fuse. The circuit's within a domestic environment have a level of diversity applied to them, this is where it is not expected for every thing to be on at any one time e.g. a couple of 7kw electric showers and the cooker and hob all pulling full load as that would most likely blow a 60 amp incoming fuse.

I would take a supply for the garage off the incoming supply through a fused breaker at the meter and then on to a garage CU.

I suspect your 60's breaker is in fact a 60 amp fuse.

Bob

AlaninOz11/10/2014 15:46:30
15 forum posts

In the mid 90's I built a new house and with consultation with my Sparky, whose wife worked with me. We determined that my peak amperage would be 130 amps so I had to have 3 phase. Australian wiring standards are different to UK, no ring mains, and each power & lighting circuit is wired to the meter board. Electric heaters were wired direct to the meter board via circuit breakers and 3 lighting went to 1 RCD, 3 power for TV etc. to another and workshop power was 2 x 15A plug circuits to RCD's for power tools and 2 more direct to CB's on meter board for lathes, mill & welders. I later had a 25A circuit added for a split system air conditioner which did not overload the supply but the Sparky said not to add any more circuits as there was no more room on the meter board.

Alan

Phil Whitley11/10/2014 16:31:11
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1393 forum posts
147 photos
Posted by Swarf, Mostly! on 11/10/2014 11:03:36:

Hi there, all,

It seems nowadays to be commonly thought that the more RCDs and/or RCBOs you throw into an electrical installation, the safer you will be.

You might be safer from electrocution but you could easily die of frustration! My point is that nobody (except the IEE Regs, sorry, BS7671) ever seems to mention discrimination.

It's important that, if you get a fault, the protective device that trips should be the one closest to the fault. The installation design should avoid/minimise nuisance tripping that takes out good circuits along with the faulty one.

If the structure of your wiring 'tree' has several RCDs and/or RCBOs in cascade, all of the same fault current & trip time rating, it's unpredictable which one will trip first. Read the catalogues of the popular suppliers and see how often/rarely there is any mention of those parameters!

While I'm at it, I'll chuck in this one too - if all your domestic installation is 'protected' by a single main RCD and, while you're on holiday, a spider commits hari kiri in some remote junction box, you're going to experience an awful pong when you return home and open the freezer door! IMHO there are some appliances whose character and situation are such that RCD 'protection' is OTT - a sound CPC should be enough!

Best regards,

Swarf, Mostly!

Absolute common sense!!, but you try convincing the IET of it! One thing that makes them all mumble and look the other way is when you tell them that RCD's, MCB's and RCBO's are NOT FAIL SAFE!! If they fail internally (and who knows where they are actually made?) then the only protection remaining is the fuse in the supply equipment, which is occasionally 60, but usually 100amps! That is why we have to calculate the prospective fault current!

Phil

Speedy Builder511/10/2014 21:33:16
2490 forum posts
196 photos

Why don't you do it yourself. This is how a French lecturer in Electrical Installation wired his house. It passed the inspection prior to sale.

frenchwiring.jpg

Chris Denton11/10/2014 22:01:03
275 forum posts

Personally having kids at an inquisitive age and a workshop that uses suds I have an RCD on everything.

Most of us have auto-transformed in our houses now in things such as phone chargers, these are mass produced for the lowest possibly price, a fault in the winding can cause 230v on the output. A slim chance but it gas happened and killed people.

Circlip12/10/2014 09:44:26
1424 forum posts

And just to throw another spanner in the works, many years ago, Christmas day morning, 8am, main 60amp service fuse decided to go bang. 8.15am Lecky board were there replacing it which again went bang when living room light was switched on. (before he'd gone)

Living room chandelier? One 60 watt blub "Protected" by a 5 amp fuse.

 

Regards Ian

Edited By Circlip on 12/10/2014 09:45:00

JohnF12/10/2014 11:56:56
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1120 forum posts
183 photos

regards JohnHi Joe, What I have is from the main consumer unit in the house is a sub main to both the garage and my workshop, two sub mains, then each location has a consumer unit with RCCB's etc.

Regarding welders my mig woks just fine off a standar socket but I was having a problem with my Tig.which is a small industrial unit, a bit old but quite sofisticated, this tripped the power on startup so consulted a pal who is a competent spark and he fixed it by fitting a different rating or type of RCCB these are rated by different letters which will solve the problem with welders start up current draw. You need to mention this to your spark and he will be able to advise. If you need to know what I have fitted PM me and I'll send you or post the details.

Regards John

Phil Whitley12/10/2014 12:03:47
avatar
1393 forum posts
147 photos

Hi Circlip/Ian.

Sorry, but that is a wind up on someones part, in order for the 5 amp fuse to carry enough current to blow a 60 amp fuse it would have to carry about 90 amps, less if the supply fuse is an HRC (high rupturing capacity) type, even allowing for the most generous fusing factor of 1.5 times the rated current, a 5 amp fuse will carry 7 1/2 amps before it blows. The chandelier cannot have been protected by the 5 amp lighting fuse, which means probably that it is not fused at all, and needs investigating as a matter of priority. Electricity is usually governed by the laws of physics (not always, see lighning) I have investigated electrical faults like this before, and usually found that what appears to be happening, is not actually the cause of the "unexplainable" On one occasion a previous owner had very carefully arranged his wiring so that the stuff used the most often, bypassed the meter, and thus the only protection was the service cut out fuse! very dangerous. You must remember that the Lecky board man is trained to do the job he does, but generally they are not trained as electrical engineers.

Phil

JoeT12/10/2014 12:24:20
24 forum posts
Posted by Bob Brown 1 on 11/10/2014 12:13:52:

The main fuse on the incoming supply should give you an idea of how much power you can pull off the supply, I would be surprised if you could actually pull the full load if the main fuse is old. The CU breaker current does not have any bearing on how much power you can pull, the rating on them is only an indication of what load they are rated for. It is not unusual to see a 100 amp main breaker in the CU but only a 60 amp main fuse. The circuit's within a domestic environment have a level of diversity applied to them, this is where it is not expected for every thing to be on at any one time e.g. a couple of 7kw electric showers and the cooker and hob all pulling full load as that would most likely blow a 60 amp incoming fuse.

I would take a supply for the garage off the incoming supply through a fused breaker at the meter and then on to a garage CU.

I suspect your 60's breaker is in fact a 60 amp fuse.

Bob

Hi Bob - thanks for that - it hadn't even occurred to me to think of getting the new CU run directly from a new fused supply after the meter. This would also prevent me tripping out the main CU if anything in the garage tripped an RCD - as others have mentioned, that's not ideal, to say the least!

Here is a picture of the old bits in my fusebox - I'm no expert, but to me that looks like an incoming fuse and some sort of resettable breaker...


fusebox I am guessing I'd need to get the leccy board involved to wire up another fused breaker post meter - unless the sparky is mad enough to work on live, unfused mains!

I'm not sure who 'the leccy board' is these days - is it the people I send the money to, or the consumer-facing side of the national grid?

JoeT12/10/2014 12:28:52
24 forum posts
Posted by JohnF on 12/10/2014 11:56:56:

regards JohnHi Joe, What I have is from the main consumer unit in the house is a sub main to both the garage and my workshop, two sub mains, then each location has a consumer unit with RCCB's etc.

Regarding welders my mig woks just fine off a standar socket but I was having a problem with my Tig.which is a small industrial unit, a bit old but quite sofisticated, this tripped the power on startup so consulted a pal who is a competent spark and he fixed it by fitting a different rating or type of RCCB these are rated by different letters which will solve the problem with welders start up current draw. You need to mention this to your spark and he will be able to advise. If you need to know what I have fitted PM me and I'll send you or post the details.

Regards John

Cheers John, yes TIG is what I'm after - I'm doing an evening course at the moment, but it's tricky not being able to practice outside class. And in a chicken-vs-egg kind of way, I only took the training because I can now probably have a TIG setup at home...

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