IEE regs too complex?

[Handyman]

I just acquired the On-site Guide to the IEE regs, on the recommendation of a respected contributor to this forum. Whilst it is useful, it is frustratingly incomplete. Example 1: I now know the zoning areas in bathrooms, but have no idea of what I can install in these zones. Example 2: I know all about wiring requirements of TT and TN systems - but nowhere does it tell me what TT and TN actually mean. Example 3: Inspection seems to be restricted to electrical tests. I could test out a circuit which works perfectly well electrically, but has been installed badly.

The qualified electricians amongst you will no doubt refer me to the full IEE regs., but for my own domestic purposes, there's just too much information in there which is irrelevant (e.g. I don't have a lift in any of my properties).

So, my question is, what book would you recommend where I can read about practical electrical installation principles in domestic dwellings? What book will tell me that I must put a rubber grommet in a back box knockout, or show me a wiring diagram for 3-way light switching, or tell me what the difference is between type B or type C mcbs? (What is the difference??)

 

[il78]

As with the On Site Guide most electrical installation books will cover all areas and most not required for your purpose.....

To use the On Site Guide you should have knowledge of BS:7671, IMHO.

And I cant think of any decent books to hand.......

The IEE technical manual is a handy piece of kit.....dont how much it is though....

 

[oilman]

So, my question is, what book would you recommend where I can read about practical electrical installation principles in domestic dwellings? What book will tell me that I must put a rubber grommet in a back box knockout, or show me a wiring diagram for 3-way light switching, or tell me what the difference is between type B or type C mcbs? (What is the difference??)

This is not meant to be a flippant reply, but you could try one of the Readers Digest manuals.

A grommet will not appear in the regulations, as it is engineering practice so a regulations book is probably not what you need.

 

[Handyman]

The grommet example was only illustrative (and from an engineering point of view, arguably a waste of time, since there is no movement between the cable and the box). But what about using metal back boxes? Or where you should use a junction box or a terminal strip. Or the correct method of extending ring & lighting connections to install a new consumer unit. These problems are very common when renovating property. Surely, there must be accepted guidelines for these sorts of things?

 

[hsiboy]

Handyman,

i cant think of a publication off the top of my head, there were some books published in the fifties and sixties (don't laugh) that will detail when to use a metal back box etc. Many things like that haven't changed in years, because they are common sense. The IEE Regs (Now BS) are not intended for a DIYer, however keen. They are intended for (and i quote from the regs) "skilled" people, that is, people who have been trained at a recognised college / institution.

I understand what you are asking, and why you are asking. But i'm afraid there are no easy answers (perhaps deliberately).

Mostly, common sense should prevail.

Its interesting to note that the regs do not state how a cable should be laid. It does state how they should be fixed, and how many can be laid side by side etc. But it does not state that you should not place wires buried in plaster around door frames, or behind skirting boards.
It assumes that the reader will use his / her knowledge and a large slice of common sense and install the cables away from external interference.

BTW

TT and TN and all the others, are fully explained in the on site guide.

Stuart.

 

[Handyman]

Thank you, Stuart. When I sold my last house a year ago, the new owners had a survey done. Amongst other things, their surveyor reported that several of the light switches upstairs were fixed into wooden boxes in the plaster (the house was built in 1960, and I hadn't bothered to change the upstairs switch wiring). The surveyor reported that the wooden boxes were a fire risk and should be changed to metal ones. He also reported that the earth bonding to the gas pipe was 2m from the meter, and not 600mm. These and other minor deviations from current practice, in turn, implied cost, which, along with other things he found, the prospective buyers then tried to negotiate off the price of the house. I told them to pay the full price or p*ss off. They paid the full price, and, as I now know, the switches are still in their "dangerous" wooden boxes. The thing is, what regulations or code of practice was the surveyor working to? Or was it bullsh*t? It's this sort of thing which I want to avoid when renovating my current property.

Example: Regs require Earth bonding 600mm from meter.
Electrician's answer: Stick to specified 600mm, cost about £150 because it's necessary to lift carpets, drill walls, sink cable in trench across doorway next to incoming pipes, etc, etc.
DIY answer: Settle for 2m, cost about £5 in bits, since no need to lift carpets, etc, as cable goes inside nearby kitchen unit.

In this instance, common sense prevailed (since the conductivity of 1.4m of 15mm copper pipe makes not a lot of difference to my personal safety) but it was/is outside the regs. Hence my query for some sort of definitive guide.

 

[il78]

Your lucky really....the surveyor could of turned round and told the prospective buyer to get an electrician in and carry out a inspection and test, and they could of gone to town......

But its good to have some electrical knowledge......

To answer your question:

Main equipotential bonding conductor to be installed within 600mm of the meter or nearest practicable point.

 

[oilman]

The grommet example was only illustrative (and from an engineering point of view, arguably a waste of time, since there is no movement between the cable and the box).

Why ask a question that's a waste of time? and then go on to imply so?

Plastic conduit would normally extend into metal boxes to protect the cable from the edges. The edges of the holes are formed by shearing. This leaves sharp edges. If, for whatever reason plastic conduit is not used, what are you going to do about it? You say grommets are a waste of time as there's no movement. Is this true? There are sharp edges, if the cable presses against these edges the insulation, being plastic will start to flow. If you plug a 3kW heater into the socket which is mounted on the box, the cable will heat up. The heating will be a small amount of direct heating, but mostly heat generated by the resistance of the fuse and the connecting terminals. This temperature increase will make the insulation softer and so it will flow more until the edge of the hole cuts through the cable and causes a short circuit.

I have seen this happen without the temperature rise.

So is it a waste of time?

The IEE regulations describe the larger physics considerations and what limits installations should be designed to. They are not intended to tell you how to implement them. In the same way motoring law tells you the limits, not how to drive to stay within them.

 

[Handyman]

or nearest practicable point.

Ah, those are the magic words he forgot

In the same way motoring law tells you the limits, not how to drive to stay within them.

...and the Highway Code provides an easy to understand, diagrammatic interpretation of the practical aspects.

That's all I'm after: A similar guide for domestic electrics. All this debate about grommets and conduit is entertaining, but it's worrying to note that the only document so far suggested is a Readers Digest Guide. Is this what everyone uses? Surely, the expert electricians out there can suggest something better than that?

 

[sparky (sfd)]

do you want the regulations or just an elctrical book to show how the work is done

have a look in a book shop under wiring and lighting all the work shown in these books will be to regs.

 

[BR]

Handyman, I was working at a house here in ireland when a young boy (10) arrived (son of the owner) He engaged me in conversation and at the end of it I was utterly amazed at his knowledge of domestic wiring systems. I asked him where he had learned this, he produced a copy of The "Collins Complete DIY Manual" (British) I thought this gave an excellent basis to anyone wishing to learn domestic electrics (up to a reasonable level). It explains in simple to understand language with loads of photographs and illustrations. I was so impressed I bought a copy (500 pages on 10 topics incl. electricity) and regularly photocopy from it for the leaving cert (I think this is similar to 'A' levels) engineering class I take once a week. I would strongly recommend this book. Well worth the €50 I paid for it. (Blue cover)

 

[securespark]

Hi

The best way to extend wiring is always to use a proper junction box rated at least to the rating of the circuit or mcb (ie if a ring main circuit then 30Amps) this way, there will be no danger of overheating or any danger of direct contact (see regs) with live parts (like there would be with a terminal block). The only exception is if you are dealing with a high powered shower circuit (between 30 -50 Amps) I don't know of any junction boxes that are rated this high.

With regard to reading material, make sure that whatever you buy is bang up to date. I bought a DIY book a few years ago and looked through the electrics section for a laugh. It mentioned RCCB's (now superceded by RCD's) and had a picture of a consumer unit (billed as the latest) that was at least 15 years old!!

 

[GwaiLo]

Handyman,
As a Surveyor I can comment on your post regarding the surveyors report.

When I am engaged to carry out a pre purchase survey it is my job to warn a prospective purchaser about any and all problems, existing and potential, that I can reasonably discover. If I fail to do that I have not done my job properly.

Surveyors do not have the skills or knowledge that specialist engineers (electrical, mechanical, gas, etc) have and so what we invariably do is one of two things. If we see something that we suspect might be (note suspect might be, not know is) a problem we have a duty to report it and comment (often commenting upon the cost of remedial works or the effect on value) upon it to the best of our ability. All surveyors (unless perchance they were qualified electricians too) would provide those comments and recommend further inspection and reporting by a qualified electrician. If we do not see a problem we do not state that the electrics are OK, merely that we could not see any apparent problem, but we still suggest that (if the purchaser wants full assurance) they consider a seperate inspection and testing of electrics.

So in short surveyors do not work to any "code", but use thier broad knowledge of matters such as regulations, property law, etc. In the case of electrics I personally always point out (where it is evident to me) that electrics do not comply with IEE16, but in those cases where I think the non compliance is a minor matter I gently suggest inspection by an electrician might provide reassurance. I also know electricians who are sensible and pragmatic about these things and am happy to recommend them to clients. Where I see something that I feel may be more serious I advise they should not purchase without an electricians report.

What you get from a surveyor is two things. You get facts....he'll tell you what he saw. But you also get an opinion, and we are all entitled to our own professional opinions. After all I have to pay a lot of money for professional indemnity insurance in order to practice and if I get it wrong and get sued my insurance goes up.

What the purchaser then does is entirely thier own decision.

 

[Handyman]

Steve, thanks for your Surveyor's input. Your stance on these things is, of course, absolutely correct and, indeed, is what you're paid for. Having seen it written down and thought about it a little more, I can now appreciate your (and perhaps all surveyors') points of view. In my example, the new owners have (so far, at least) chosen not to take any action.

The best way to extend wiring is always to use a proper junction box

Not practical: There's not enough space to fit 20 JBs

BR from Ireland: Your Collins Guide seems the best suggestion yet especially if it's based on the IEE regs. I will investigate further. Thanks.

Other "experts" have suggested The Electrician's Guide to the 16th Edition of the IEE Wiring Regulations
http://www.amazon.co.uk/exec/obidos/ASIN/0953788512
Any comments on this? Will this tell me what I want?

 

[hsiboy]

When I sold my last house a year ago, the new owners had a survey done. Amongst other things, their surveyor reported that several of the light switches upstairs were fixed into wooden boxes in the plaster (the house was built in 1960, and I hadn't bothered to change the upstairs switch wiring). The surveyor reported that the wooden boxes were a fire risk and should be changed to metal ones.

Well, its a sticky wicket this one.
Q. Are the wooden boxes safe (as is)? A. Probably - hard to tell without an inspection.
Q. Are the boxes a fire risk? A. wood is combustable, so yes.

But if wooden boxes were in place, i would be more inclined to check the state of the wiring.

I bought our house, with two electrical points noted by the surveyor.
1. There is a light switch, with surface mounted (clipped to plaster) twin and earth pvc cable in the old larder.
2. The lighting arrangement (wall lights) on the landing seems unusual.

What the surveyor didn't catch was the total lack of earth in the house, it had failed a long time ago.

The house only has a 40A cut out supplied via cloth and lead covered cable (condition suspect ~6mm conductors). At some point soon i need to dig up the drive and lay a new cable.

So as you see, the surveyor spotted two things he thought looked out of place, but missed the big stuff. He did that elsewhere too, but thats a different story.

He also reported that the earth bonding to the gas pipe was 2m from the meter, and not 600mm.

The regs require that bonding be carried out at the entry point into the building. And suggest that this occurs no more than 600mm from the meter. in chapter 54 section 7 sub section 02 of the regs, (page 24ish onsite guide i think), it states, at point of entry to building, or 600mm from meter. What they are preventing is someone bonding pipes further away from the meter, that may have been coupled to the meter via plastic.

Many houses have plastic gas main, and only copper internally, so using common sense suggests you concentrate on the copper inside, but some gas installs are via steel or iron pipework, so you need to understand that this could offer a path for a fault current in the event of failure, but it may have a relatively high resistance, and so we bond it.

Your electricity supplier can tell you the fault current available, and you may find that (on paper at least) that your 2 metre wire could have to carry in excess of 400amps until a fuse blows.

Stuart.