Wiring in Garage/ caravan etc

[russellsmiler]

Ok this is my first post, and I hope i can explain what i am trying to achieve.

I have an electricity supply which is 2 wires from a pole, the wires are exposed (about 25mm2) and are up on the outside wall , coupled to those wires are one sheathed cable neutral, one sheathed cable live, they come down the wall and through to by my consumer unit live goes through the electric suppliers fuse (100A) nuetral goes through the connectors also part of suppliers fuse, through meter to my consumer unit.

This all seems normal would you agree !!

Inside consumer unit all curcuits are wired as you would expect, however the earth terminals are connected back by way of 16mm yellow/green into the neutral at the 100A fuse...again i believe this is all as it should be and in fact was checked by the suppliers as part of a safety inspection visit.

SO...I want to put a supply to my outbuildings a subsequently my caravan.
I have a pucka terminal block at my side of the meter that is fed both live and neutral by 25mm cable...i propose to come from this...through a 60amp 30 millibar rcb then run the 25 meteres to the outbuildings...my 16mm swa cable is 2 core...i am proposing to use the wire as earth but do I need to do this?? It seems that my neutral is the earth so as long as i link any earths from circuits and caravan back into the neutral at the consumer unit it will be ok....does this seem right or wrong

Thanks for any discussion
Russell

 

[ban-all-sheds]

Inside consumer unit all curcuits are wired as you would expect, however the earth terminals are connected back by way of 16mm yellow/green into the neutral at the 100A fuse...again i believe this is all as it should be and in fact was checked by the suppliers as part of a safety inspection visit.

Why the "however"?

TN-C-S supply, and as you say, the DNO are happy that it should be.

SO...I want to put a supply to my outbuildings a subsequently my caravan.

Outbuildings, possibly.

http://electrical.theiet.org/wiring-matters/16/elect-inst-outdoors.cfm?type=pdf

Caravan - no way. You may not use TN-C-S to supply a caravan, you'll have to have a TT supply for that.

I have a pucka terminal block at my side of the meter that is fed both live and neutral by 25mm cable...i propose to come from this...through a 60amp 30 millibar rcb then run the 25 meteres to the outbuildings...my 16mm swa cable is 2 core...i am proposing to use the wire as earth but do I need to do this?? It seems that my neutral is the earth so as long as i link any earths from circuits and caravan back into the neutral at the consumer unit it will be ok....does this seem right or wrong

It's very dangerously wrong in more than one way.

You're proposing to have no overcurrent protection for the SWA apart from the supplier's fuse.

You're proposing to combine neutral and earth in your installation.

Add to that the fact that you think you can supply a caravan with TN-C-S.

You don't understand enough, or know enough to be doing this work. Have you even confirmed, for example, that the armour of the SWA would make an adequate cpc? What about testing?

The work is all notifiable.

Installing an earth rod and checking that it works is not really a DIY task.


Please get an electrician.

 

[russellsmiler]

Thanks for shooting me down ban-all -sheds

Not sure if i have described what i am doing properly, you say i am not protecting the SWA (Steel Wired Armour)

have a pucka terminal block at my side of the meter that is fed both live and neutral by 25mm cable...i propose to come from this...through a 60amp 30 millibar rcb then run the 25 meteres to the outbuildings...[/

By the way I am seeking advice, not about to embark on doing something Stooopid

Why is it everybody thinks that because you dont know something that means you cant learn...i am NOT an electrician, however that dosent mean i dont have the right to glean information regarding this simple science.

So if someone could talk me through what i should do in a jargon free way it would be appreciated.

Thankyou all who wish to help
Russell

 

[ericmark]

The supply to a caravan is not simple. Much will depend on distance between caravan and building with extraneous-conductive-parts.

In the UK the ESQCR prohibit the use of a TN-C-S system for the supply to a caravan or similar construction.

However it would be dangerous to have a caravan with metal exterior next to for example a cast iron drain pipe where one could touch both at the same time. In theory this can't happen as fire regulations give a minimum distance for caravans so in CARAVAN / CAMPING PARKS AND SIMILAR LOCATIONS using TT from the TN-C-S supply is not a problem. But when stored at home and power taken to them to charge batteries it is some times necessary to remember it's not a caravan park but a domestic home and one has to consider the risks.

The problem when not following BS7671 to the letter is to convince the guy responsible for the safety of the installation that what you want to do is safe. Be that an electrician to his scheme provider or anyone else to the local authority building control. Therefore I would detail your intentions when you apply for permission so that it is all sorted out before you start not after completion.

You will need 30ma RCD protection for the caravan supply and also it has to be all pole since overload protection is also required a RCBO would seem the way forward.

To install an earth electrode (rod) will require meters not normally kept by any DIY guy and add the cost of hire even if one does know how to use it to the LABC charges and it is likely there will be little or no saving to DIY this job.

So I would say forget DIY get an electrician who is a member of a scheme to do the work and sign it off it's just not worth DIY with this type of work.

 

[ban-all-sheds]

Thanks for shooting me down ban-all -sheds

No problem.

Not sure if i have described what i am doing properly, you say i am not protecting the SWA (Steel Wired Armour)

have a pucka terminal block at my side of the meter that is fed both live and neutral by 25mm cable...i propose to come from this...through a 60amp 30 millibar rcb then run the 25 meteres to the outbuildings...[/

A 60amp 30 millibar rcb (sic) does not provide any overcurrent protection.

By the way I am seeking advice, not about to embark on doing something Stooopid

You will be if you embark on DIYing this with your current knowledge.

Why is it everybody thinks that because you dont know something that means you cant learn...i am NOT an electrician, however that dosent mean i dont have the right to glean information regarding this simple science.

However simple it is it is not knowledge-free. You probably think it is simple because you have absolutely no concept of the scope.

So if someone could talk me through what i should do in a jargon free way it would be appreciated.

Nobody has used any jargon. If they have used technical terms you don't understand that is because of your ignorance, not a failing on their part.


The thing is, wiring outbuildings and caravans, installing new CUs, outside supplies, submains etc is not a trivial job, and I can assure you that it involves knowing far more than you think it does.

Asking questions here can be a useful part of a learning process, but they are not a substitute for proper structured studying. The key term there is "learning process" - you cannot learn all the things you need to know just by asking questions here. It isn't structured enough - it won't provide you with a way to progress where each step builds on what you learned before.

You can't carry out a job of this magnitude by asking whatever random questions happen to occur to you. You've already shown that you have some very serious gaps in your knowledge, and lack of understanding of some very basic concepts. What if you get something wrong because you have no idea your knowledge is wrong? What if you miss something because you simply have no idea it even exists, and just don't realise you don't know it?

• //www.diynot.com/wiki/electrics
  
  
• //www.diynot.com/wiki/electrics:books
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/electricity.html
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/domesticinstallations.html
  
  
• http://www.tlc-direct.co.uk/Book/1.1.htm[/list]I suggest you get stuck into the last link right away - it won't give you design ideas, and unfortunately it doesn't refer to the current edition of the Wiring Regulations, but it's free, and will still give you a good grounding which you can augment with more up to date publications. Don't rely on it exclusively, but if you want to learn the fundamentals of circuit design it's of value.
  
  
  

  Thankyou all who wish to help

  Hopefully nobody will "help" you by "talking you through" what to do - you must not do any of this without a full and genuine understanding of everything you are doing.

 

[ericmark]

What BAS says is correct. We all realise that most people don't understand what they are doing but get away with it. And we also realise if we just say you can't you will have a go anyway. So I at least try to make people realise it's not just a case of join the dots.

Yes we can use terms like loop impedance and it will seem to many we are using jargon but what we are doing is making sure if there is a fault that the automatic disconnection device be that MCB, Fuse, RCD or RCBO will work and make the system fail safe should something go wrong.

If I take one example the MCB this is a small device with what looks like a switch found in the consumer unit. This is two devices built into one, one thermal the other magnetic. Because the thermal part is slow to act the magnetic part is added so if you have a short circuit the miniature circuit breaker (MCB) it will disconnect in micro seconds. However if this was the same value as thermal part because when things start they use more current it would be always tripping out so it is made 5, 10, or 20 times bigger than thermal part and is given a letter B, C or D.

So a B32 MCB will trip out with magnetic part at 160A. So when we use one in a circuit we have to measure how much current can flow with a short circuit. Since ohms law gives a fixed relationship between amps and ohms at a fixed voltage in this case 230 volts then we know the circuit must measure 1.4375 or less ohms because AC not DC this is called impedance not resistance. At the consumer unit with a TN-C-S supply we should have 0.35 ohms or better so we have 1 ohm to play with.

Not rocket science but still needs working out. So with 10mm sq cable at 0.0044 ohms per meter approx we can have around 245 meters before we have a problem. However this is theory and in practice we really need to measure the value so we use a loop impedance meter.

We will normally have three meters the loop impedance meter will also measure prospective short circuit current. Our insulation meter which has to measure at 500 volts will also measure low ohms at at least 200ma. And finally the RCD tester which will measure the time and current needed to trip an RCD. When we send these to be calibrated it will likely cost us £75 for the week to hire replacements.

Add to this the £100 minimum charged by LABC plus vat and we can say it will cost the normal DIY guy £250 to get all the paperwork he needs when working in a special location which you are.

So unless doing a really big job like a whole house re-wire it is unlikely to be worth while to do as a DIY job this is a legacy from the Labour government called Part P.

Now to measure the loop impedance one can easy raise the voltage of anything connected to earth to line voltage so of course some very careful precautions must be taken.

To train an electrician to do these tests colleges run 12 week courses one night a week to get what we call C&G2391 and have a high failure rate of even time served electricians.

I think it can be seen that to teach this on a forum is just not going to work.

We have to judge if one the guy we are talking to will be able to do the work and two will any other reader copy it and cause an accident. This does limit what we will say on an open forum.

If you really in spite of it likely costing you more than getting some one in to do the job still want to DIY we all will help. However you can't expect us to do a paint by numbers job you do need to read up the major parts and ask when you get stuck.

 

[ban-all-sheds]

this is a legacy from the Labour government called Part P.

Although the consultation document may have been issued in 2002, it contained the results of the Regulatory Impact Analysis (performed by Civil Servants, not politicians) which must have taken a while, and the first edition of Approved Document P (ditto).

The whole process which led to the consultation document being issued kicked off in response to the Construction Industry Deregulation Task Force’s 1995 report which recommended amongst other things that the Building Regulations should address electrical safety and that the administrative burden on builders should be rationalised. The Government at the time responded to these recommendations by agreeing to review the case for new requirements and how they might best be practically introduced.

Blair/Brown/Prescott were nothing to do with the Government in 1995 (some bloke called Major was in charge), and between 1997 & 2002 there were a few other distractions, like handing back Hong Kong, wars in Kosovo & Afghanistan and the run-up to the 2nd Gulf one, Scottish & Welsh Devolution, House of Lords reform, Foot & Mouth crisis etc. When a report produced after years of work by civil servants and industry experts telling them that painstaking and diligent research showed that this proposed legislation, supported by hundreds of relevant and expert bodies, would save lives arrived it was not unreasonable for them to say "OK, we'll lay it before Parliament", rather than starting all over again to verify the work already done. That's how governments work and that's what would have happened whoever had been in power.

 

[Paul_C]

When a report produced after years of work by civil servants and industry experts telling them that painstaking and diligent research showed that this proposed legislation, supported by hundreds of relevant and expert bodies, would save lives

But, unfortunately, (a) that supposition was not actually backed up by reliable evidence in the first place, and (b) after it was introduced there were no statistics to show that it actually had the claimed effect.

 

[russellsmiler]

Ok so I have decided to carry on and do the instalation

This is the stage i am at

From House to brick and slate stables have run a 16mm twin SWA cable,
this is isolated by way of a 60 amp isolating switch in main house.
Earth is by way of armour wire and is only earthed in house.

In stables distribution is as follows.

Caravan
Caravan as its own Dis board, all mcbs are to a 40a 30mA Dp RCD
I have used 10mm 2 core SWA from stables to caravan armour being the earth.

Adjacent Tin Shed
Similar setup
Tin shed as own dis board ewith 63a 30mA DP RCD
i Have used 10mm 2 core SWA from tin shed to stables armour being the earth.

In stables
I am not finished but propose!!
Split consumer unit
16mm Cable from house(not earthed in stables) incoming into 63a breaker
10mm For caravan into 40a breaker
10mm for tin shed into 40a breaker
Lighting to stables 6a breaker
sockets to stables 32a breaker with rcd protection.

EARTHING
from this board i am running 16mm earth down inside wall were it goes underfloor to external i have hammered three steel pins 25mm Diameter, 800mm long 600mm apart in a triangular fashion, i have had pins engineered so i can clamp earth cable on, and have protected with denso tape (messy Stuff), The caravan, the stables, and the tin shed are all sharing this earth.
the main 16mm cable earth is NOT part of this earth setup.

So am I heading in the right direction, the installation looks the buisness with very good attention to quality of cable clipping neatness.

Your comments please

 

[ericmark]

You must test the earth. When putting in earth rod in a gas terminal to get the required earth could be anywhere between 3 and 6 rods each 1.2 meters long. You can't guess you must measure.

There are two methods. The proper earth testing rig uses test earth spikes and is quite complex and is used when there is either no power or the power comes from a non tested device like a generator.

The supply you have will be tested so you can compare your earth to the suppliers earth and it will be within the 16 ohms of the suppliers earth. i.e. the reading can be up to 16 ohms out. But since normally looking well above that it's not really a problem. You may also need to allow for volt drop in your cables but again that should not be enough to become a problem.

So what is the reading you got for your earth? Also what will be the gradient should there be a fault between the house and out buildings? Remember four legs have a bigger problem to 2 legs.

So if you read Fig 705 in BS7671:2008 see here for some of details you will see how important the earth is. It's not just the reading but gradient. Hope your live stock is not too expensive. Unlikely insurance will cover if not done correctly.

 

[ban-all-sheds]

Ok so I have decided to carry on and do the instalation

So you came here for advice.

All the advice was "don't DIY".

That was not the advice you wanted, so you decided to ignore it.

You're a fool.

From House to brick and slate stables have run a 16mm twin SWA cable,
this is isolated by way of a 60 amp isolating switch in main house.

So still no overcurrent protection.

You still don't have the first clue how to do this properly.

You're a fool.

the installation looks the buisness with very good attention to quality of cable clipping neatness.

Oh well, that's OK then. As long as it's neatly clipped that's all that matters.

Your comments please

You're a fool. Go away.

 

[NewOrder]

If you don't notify this work and it goes wrong, I assume you're aware of the possible consequences?

Now there is one thing perhaps adding a socket in a kitchen and not notifying it, but what you're proposing to do does carry real risks.

However I realise some people just go ahead anyway and at least you are seeking advice on the issue.

 

[skotl]

Jeez. I'm with BAS, Eric and Joy.
Why did you come on here asking for advice and then proceeded to ignore it?
Scarey.

 

[russellsmiler]

I really dont understand the fuss

Just to let everyone Know, The comments here have given me loads of guidance.

I probably have more practical experience than this community gives me credit.

project managed, in the region of hundreds of house builds, six nursing homes, childrens nurseries, Loads of Modular ( additional Classroom) type projects.

All of these including overseeing the M&E installation
Almost as relevant the temporary electrics for site cabins etc
also with the modular build its usually very much a see what the existing meter cupboard as to offer in the way of spare capcity, and then work closely with the electricians to make it work.

I have worked with numerous electrical contractors and electricians, I have seen how the job is done and on Many Many occasion pulled sparkies on the quality of the work.

I have built 2 houses and have renovated 2 houses, i am currently on my final resting place project, hence the need for caravan and stables.
All my own building work I have done the electrics completely.
I always have my work inspected and tested and certified, (usualy by a national contractors testing team) (perk of being a company project manager)

I probably come over as thick on this forum...I like dumbing down when doing my own projects.

I think the advice that does not get given here is that most installations are 95% infrastructure, if a diyer can get the infrastructure done properly i think you only need an electrician to tie in the ends. or even have a go at that yourself, It really is quite simple stuff.

I would love this Man Ban all sheds to be involved with the real world of electrical installation instead of thinking he is a superior being.

Anyway will have my electrician come and test in the next few days....if i have to make a few changes..i learn some more..just to make it clear..

I NEVER let any installation go live until proffessional testing as took place and a certificate issued.

As for building control....Do any of you realise how many Clowns are at large in this country, in the disguise of abuilding control officer !!

 

[BigRobCanUFixIt]

tick, tick, tick, tick, tick, tick, tick,








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BOOM! (unleash BAS) haha....