The Shop => Our Shop => Topic started by: Arbalist on June 20, 2014, 04:52:58 AM

Title: Workshop Electrics
Post by: Arbalist on June 20, 2014, 04:52:58 AM
I'll get an electrician in to hook things up but I'll probably do the wiring myself in my new shed. Thought I'd need just a simple two way consumer unit until I started looking, now I'm getting confused. Too many choices, can anyone help me out!

I'll be putting in four fluorescent tubes for lighting and a simple ring of metal clad sockets with the wiring in plastic conduit. Think six doubles should do it.

Title: Re: Workshop Electrics
Post by: lordedmond on June 20, 2014, 07:54:08 AM
I have the first one installed , my next statement is qualified with me being a time served sparks when I left school at 15 that was 51 years ago I am not a house brasher but more industrial leanings

They all suffer with one drawback with the RCD on the incomer if you have a fault that trips the RCD it all goes off and you are in the dark , you need a unit that has a normal breaker for the incoming and the RCD on the ring main cct.

Now comes the crunch with RCD and workshops that we use it's the VFD drives that have delta filters on them the will ,do trip RCD with the delta caps passing enough to earth to trip it , not all do it

My Myford does it and I have tested it carefully and it ok ,it's the filter for the odd order harmonics that cause it to fault the RCD when you switch off the lathe.

Now you may ask what I have done to sort it ,I have disabled the RCD my choice ,not recommended but I have things earthed correctly and I am confident that I am safe , I have also put in a copper earth rod local to the WS and I know this is good because I have tested it and it's less than 0.1 ohm

If you are not sure please be safe and consult a qualified sparks about this but your light must not be controlled from a RCD the must stay on when the ring main faults

Remember you cannot see it ,smell it but by ek you can feel it

Title: Re: Workshop Electrics
Post by: Arbalist on June 20, 2014, 10:19:10 AM
I kind of assumed that there would only be an RCD on the circuit for the sockets, as you say it's daft to have it on a lighting circuit. I'll have to look out for that!
Title: Re: Workshop Electrics
Post by: lordedmond on June 20, 2014, 10:38:03 AM
In the first link the mob on the left is the RCD that is the incomer the other two may be one 5amp and one16 amp not sure

Therefore the RCD controls everything

FWIW that's why in a domestic situation the consumer units are split one half has the RCD and the other not, you tend to put the lights and freezer/fridges on the non RCD side and all other on the RCD controlled side

I am old fashioned and a firm believer of earth bonding of all things that you can touch eg. Lathe and mill less than the span of your arms must be bonded with 16 mm bonding cable that way if one gets hot there will be no difference in the potential between them and therefore no risk.

With electric drill 250volt and mowers just use a RCD plug or dedicated RCD socket in case you cutt the cable

Your best bet is to get a small consumer unit and fit it out as you require normal MCB for light and a RCD for your sockets and another normal one for the ring that has your machine on.
But do not forget to bond them together and any radiators that my be in the workshop, a rule if you can touch both pieces of equipment with each hand bond it
Title: Re: Workshop Electrics
Post by: hermetic on June 20, 2014, 11:23:33 AM
Hi Arbalist,
  If you get a plain consumer unit with a 60A incomer (formerly known as the main switch) and then fit a 32A RCBO (residual current breaker overload) to protect the ring main and the standard 6A MCB to protect the lighting. As has been said above, if you are using a VFD or inverter drive type device you will have to use an RCBO which is suitable type for use with this equipment. Unfortunately nuisance tripping of RCD's and RCBO's by equipment using capacitors (vfd's etc) which filter transient voltages to earth is an ingoing problem to which there seems to be no 100% cure at the moment. At least this means your lights won't go out. I am lucky, I have three phase in my workshop, but still use fuse protection. There is nothing wrong with this as long as all the machines are properly earthed, and the earth is good. The RCD monitors the current flowing in the live and the return(neutral) or the phases in three phase systems, and trips if there is any imbalance in the readings. This still requires the machines to be earthed properly, as if it is not it will not trip untill someone touches the machine and provides a "path to earth" for the fault current. I am telling you all this to emphasise the importance of earthing all metal machines even if you are using an RCD.
Title: Re: Workshop Electrics
Post by: Arbalist on June 20, 2014, 11:27:53 AM
Thanks for that Stuart. Our main consumer unit is as you describe with sockets etc on the RCD protected side of the unit and lighting on the other. I'm really surprised you can't seem to get a simple unit for garages that has an RCD protected circuit for sockets and another for lighting. Guess I'll just pay the extra and let the sparks supply the stuff! Thanks again.
Title: Re: Workshop Electrics
Post by: Arbalist on June 20, 2014, 11:31:58 AM
Thanks Phil, we were both typing at the same time. I don't have, and don't plan to get a VFD but thanks for the information, very helpful.
Title: Re: Workshop Electrics
Post by: lordedmond on June 20, 2014, 11:41:55 AM
Thanks for filling out the details, I am dyslecic and typing out a lot of info takes me a long time

A good earth and equipotetial bonding are the best safeguards you can have followed with correct over current protection

Stay safe

Title: Re: Workshop Electrics
Post by: hermetic on June 20, 2014, 12:13:49 PM
well said Stuart, and thank you!
Title: Re: Workshop Electrics
Post by: garym on June 22, 2014, 06:08:20 AM
Very interesting thread. I installed the first one linked to by Arbalist into my garage. Combined with the other thread "Zapped by my lathe",9827.0 (,9827.0) it raises some important questions. None of my equipment is earthed other than through the mains plug and I would like to know more about what I should be doing to improve safety.

Title: Re: Workshop Electrics
Post by: lordedmond on June 22, 2014, 06:48:57 AM
Like your sig which mine would been on two crutches for years

Back to your question
Equiptensial bonding ( equal potential )

In short all the metal lumps in your WS should be connected ( bonded ) with a earth wire 16 mm sq now this can be the nice flexible cable that the car audio freaks use as long as you put a wind of earth tape to identify it as a earth conductor.

This is important when you can touch both lumps of metal with both hands ( one on each one ) volt across the heart

Note I have said metal lumps this includes central heating rads , taps , anything metal

This bonding wire should go back to the consumer unit and on to a good earth copper earth stake f
One meter long just outside the WS

Now the catch is not there always one it will not prevent a belt as I think you got due to a exposed metal part in a insulating case that has become live , now you have a live metal part and a earthed lathe  thus a potential difference , that is why those parts should have been on a earthed metal plate .

To ilustrate the point on my lathe the bolted on metal cover on the sparky bits has a bonding conductor to make sure it's all at the same potential

My history when I did the collage work many years ago earthing was a year long subject on its own

Hope that has not confused the issue. The point is even if it's on a 13amp plug they must be independently earthed as well

have you sorted the hot lathe yet?

Title: Re: Workshop Electrics
Post by: Arbalist on June 22, 2014, 10:33:20 AM
All good stuff Stuart, thanks for chipping in with that.
Title: Re: Workshop Electrics
Post by: lordedmond on June 22, 2014, 11:20:35 AM
Thanks for the comment

A point which many people think is if they have a a RCD in the circuit they are safe , they are not good earthing is the primary protection


Title: Re: Workshop Electrics
Post by: garym on June 24, 2014, 06:07:07 PM
Hi Stuart,

If Arbalist doesn't mind, thanks for your comments. I'm reasonably familiar with equipotential bonding as I did quite a bit when installing our new bathroom several years ago, but I'd never seen it mentioned in forums before in relation to workshops. It just hadn't occurred to me in the same way that, for example, bonding a cooker wouldn't. I think the three-pin mains plug lulls us into a false sense of security that equipment is electrically well designed. Obviously this is not always the case. I'm surprised the suppliers can get away with supplying equipment with such poor earthing. This post should really have been in the other thread I quoted, sorry.

Title: Re: Workshop Electrics
Post by: lordedmond on June 25, 2014, 03:28:41 AM

My comments are the result of the way apprenticeships were done in my case Stanton and Stavely sent the first year electrical apprentice to collage full time ,only then you have a mentor out on the works you the went to different plants and different mentors thus you became safe with a broad knowledge

In a works environment copper tape 1 inch by 1/8 was use to bond very thing in reach, yes it was the crowbar mentality but the fuses did blow and nobody was put in danger we had three phase volts up the 550 vac TP that the start of the killer volts

bonding to me is a requirement not something I will do tomorrow ,tomorrow may be to late.

After I finished my time I went on to degree level in electrical eng and did a paper on lightning, years later at the NAT West I continued with lots more learning inc items that were governed with fridge gasses ,Diesel engines ( biggish up to1000shaft hp) ,then more uni studying lead me to higher levels
In my core subject

So it went on with software BAS coming along , they were still sending me on university courses just before they made me redundant

now I just potter in the WS much better way of life ,I have dropped all the prefixes to my name now no point the are not needed it's just me

Title: Re: Workshop Electrics
Post by: Arbalist on June 25, 2014, 12:04:57 PM
If I can ask another question, I was planning on running a six double socket (metal clad) ring using T & E in 20mm plastic conduit. It ccurs to me though that for physical reasons it would be nicer to run two, three socket spurs from the consumer unit instead. Would this make much difference? It's only me in the shed so I can only use one piece of kit at a time.
Title: Re: Workshop Electrics
Post by: lordedmond on June 25, 2014, 12:33:55 PM

The rule for domestic instalations is you can have any number of 13amp outlet on one ring main with 32amp MCB or fuse and you can spur off from them

If you go for spurs for each socket you will need a MCB 16 amp for each one thus a larger consumer unit

For a modest WS one ring will suffice but put in twice the number of double outlet above the benches that you thing you will need

T&E in conduit is not the best way if you want to use conduit use single core cable it will be easier to poke down , but do you need to use it?

Put a couple of SS outlets down low they come in useful

Have fun and be safe

Title: Re: Workshop Electrics
Post by: Arbalist on June 25, 2014, 12:49:15 PM
Glad I asked Stuart, very good point about the T & E! I think I'd prefer to use conduit, it's not expensive and it adds another level of protection for the cable. I'll have to price up some single core cable though, it may not be cost effective ...

SS outlets?  :scratch:
Title: Re: Workshop Electrics
Post by: lordedmond on June 25, 2014, 12:53:34 PM
Forgot one very important point you mentioned metal clad SSK,s

You will need to provide a jumper  covered in earth marked sleeving from the box to the socket itself that same sleeving should also cover the bare earth conductor from the striped back T&E

As you can see it's all in the bonding.

A point the lads across the pond often demonstrate this error they place the outlets in the line of fire from the lathe or mill and they then get all the swarf thrown at them so think where you place them , never in a place where you need to reach over the machine to turn it off

Placement of the consumer unit should be just inside the entry and exit door low enough for anyone to reach just in case

If there are ankle biters about then consider a key switch to keep things under your control

I know I am very safety minded with electric but it can kill and does so we all work alone in our WS so why not make it safe at least as far as the sparky bits goes


SS outlet Switched Socket outlet dropped back into the short hand
Title: Re: Workshop Electrics
Post by: awemawson on June 25, 2014, 01:41:13 PM

What's your view on single phase sockets on three phase machines? Several of my three phase machines have such things as DRO's and lights which are single phase via 13a plugs. Machines well away from walls so cables to the wall socket would be a trip hazard.

All the three phase machines are fed via a 30 mA RCD, and what I've done (actually did another this afternoon) is to fix a single phase socket on the machine, picking up phase 1 via a suitable breaker. Machines are earth bonded. I make sure every socket is on phase 1 as that is the phase the wall sockets use.

Title: Re: Workshop Electrics
Post by: lordedmond on June 25, 2014, 01:55:36 PM
No Problem with that Andrew I would be concerned if you put another Socket on the machine from a different phase 440 between sockets  :bugeye:

keep it to one phase and you will be fine