CORGI visit - queries on regs

[Stephen Dawson]

Picky, the pipe work has no requirement to be bonded, unless in a bathroom.

[Jim Alexander]

Thank goodness I've run my system in Hep, that'll hjack the thread probably. Of course there is always the metre of copper at the boiler....

Any regulation that is ambiguous is a bad regulation and this is certainly ambiguous but I think the relevant word in relation to CH is "system" compared with water service "pipe". IMHO the CH system requirement is satisfied by properly earthing the boiler. Supplementary bonding requirements are a separate issue.

Jim A

[John]

NOT ALL boilers are constructed entirely of metal conducting materials! More and more are using plastic internal water carrying parts so there is no possible continuity regardless of how good the union/compression connections are. In the event of the installer being conscious of the possibility of a poor connection between the various pipes emanating from the casing and considering the negligible cost of five/six earth clips I can see no reason to usefully omit this reassuring bonding. Before anyone jumps in they may be useless but they provide confidence to the viewer especially in the case where heating pipes vanish beneath floors and a later visitor may not "know" that no repairs or extensions have been done using plastic pipes. I really don't see why this point has generated such a squabble

[Lobster]

Well, I did cross-bond these 5 pipes - reckon it took less time to actually do it than to read all the conflicting responses here :-) . However, from what you're saying above, could it in fact be a Bad Thing to have fitted it? Not sure about this issue of mixing of equipotential zones...

The sparks was round yesterday to do a full check on all my electrics in fact, and didn't pass any comment on any of the cross-bonding.

David

[Coherers]

My reading of the regs, the books and the stuff on the IEE website (see other posts) is that metal cold water, gas and central heating pipes do require **main** equipotential bonding connections under reg 413

The requirements for **supplementary** equipotential bonding in bath and shower rooms are given in reg 547

As for the whether the regulations on bonding all the services are really sensible or not, that is a different matter and I don't know enough to say. The impedance between, say, the cold water supply and the central heating pipework is generally negligible, but I suppose the rule is there for the cases where it isn't. As John points out, sometimes the plastic water carrying parts of the boiler electrically isolate some pipes.

[Mike]

All compression joints are in metal as far as I'm aware, and I have never seen these not mounted on a common chassis.

Partially because it is unsightly but primarily because it is this 'gold-plating' of regulations that is driving costs higher and higher. Before you know it BCOs are demanding these clips even though they are superfluous to all known reasons. Six clips costs about £2 but the cost of fitting them is much higher, even for a DIYer if you cost your time.

[Mike]

Which actually raises an issue in mine and many other cases - boilers are often external to the house.

[Mike]

You do to meet the IEC approval for most boilers. I expect there might be some around that aren't but I haven't seen one.

[Mike]

Yes

Not a gas expert but I assume this is correct

No - most ducting is floating and totally safe. If he means exposed ducting I might agree more.

Basis of this argument but shall we say some do, some don't.

No. Have you ever seen a Juliet balcony earthed for example ? Far safer unearthed I would think.

No !

Absolutely not !!!!!

Surely this would form an earth path you may not want in a PME system

All in all, you don't appear to be quoting from a reliable source. Perhaps a new handbook from a better author is required.

[Coherers]

I would think that most modern boilers will be connected to the mains and will have an earth wire in the cable which is interally wired to the frame and any exposed metal parts. As long as it is wired correctly, you don't bond it in the sense of the Equipotential bonding regs - which is what I assume was meant here.

As for boilers without an electrical supply, then I don't know.

[Coherers]

Trevor E. Marks has written courses on behalf of the IEE, has been chair of IEE technical sections and is a well known respected technical author who has written extensively on electrical subjects.

So what we have is that you think:

1) The clear quote from the IEE wiring regs is wrong. 2) A standard, well-known text, which you appear never to have heard of, is wrong. 3) A document on the IEE web-site, written by Paul Cook ( author of the IEE publication "Commentary on IEE Wiring Regulations" and who gives papers on the subject at international seminars) is wrong. 4) Engineers discussing it on the IEE web site who are also wrong.

I am sorry you don't agree with the IEE, but I am afraid they make the regulations. Take it up with them.

[Mike]

Often the electrical part is double isolated and needs no earth. There is an actual earth terminal on the front/side/wherever which must be visibly earthed. I think the boiler commissioning form even refers to checking this.

Why would these (if they exist) need earthing at all ?

[Coherers]

You only need two (flow and return) assuming the gas & water are done elsewhere. Probably one on the flow OR the return will be enough. You certainly don't need one on the DHW.

[Coherers]

Good question, but I can't explain the logic behind quite a number of the regulations. All I know is that there are there, daft/sensible as they may be.

[Mike]

Even if we ignore the contentious items, he is wrong on both the lightning and telecomms points. These are serious mistakes.

There are errors in all standards. They are the work of teams of experts usually volunteered by their companies who make a 'best-effort' on the task in hand. I have contributed to many such forums in the telecomms fields and I am sure these contain errors as well.

I'm an electronics engineer, not an electrician, and so a book on the wiring regs don't come high on my list of preferred reading. I doubt if he has heard of me either.

Quite possibly. I am often critiquing papers at seminars and find glaring errors.

As a member of the IEEE I don't think I can get to these. But I'll see if it's possible.

Don't agree with many things about the IEE, that's why I joined the IEEE 25 years ago.

[Mike]

If a regulation is daft then if you are a professional engineer you should question it and reject implementing it if it is not sensible. Brunel would expect nothing less.

[Mike]

Some idiot BCO is going to refer to that statement you have just made and before we know it boilers all over the UK will have two unnecessary wires on them. There is no need for these wires and if the regs aren't clear on the matter they need clarifying.

[Andrew Gabriel]

IEE Wiring regs have required bonding of lightning conductors for years. I believe the BS on lightning conductors does too, but I don't have a copy of it to see exactly what it says. Many electricity suppliers will refuse to connect you to the supply if you have bonded the lightning conductor. Thus it has never been possible to make it conform to all the various regs.

Bonding of telecoms equipment is a horribly complex area, particularly if you manufacture it for sale to multiple countries/PTTs. In just about all cases, it has to be bonded, but it is often done at a single point only, and kept isolated everywhere else. PTT's normally have their own wiring regulations and are often exempt from national wiring regs and EU directives on things like emissions.

[Dave]

I couldn't agree more. It's jobs for the boys here. (the regulators, that is)

Having followed this subject for the last few days, I have been moved to ask a few questions about all this cross bonding.

My working environment was in fast jets.

When we have to bond something for the purpose of lightning strikes while the aircraft is in flight, we have to ensure that parts of the aircraft are bonded to the main frame by a very low milli Ohms path. To do this, we either use, in the case of a movable part, an un-corrodible rubbing strip on an equally un-corrodible part of the structure, or a sealed bonding clip system.

Now to come to the point that has been raised about equipotention bonding of copper pipes.

Central heating and boilers use a lot of copper and brass in them. Not to mention other metals that abound in a system. Why does any one expect copper, which corrodes quickly, expect a clip or clamp to produce an effective bond, when it is open to corrosion?

If the bond is so many milli Ohms at the time is put in place, how good is the bond a few months later?

I'm just curious

Dave

[Coherers]

I doubt a BCO will refer to my posting ;-) He is likely to refer to the IEE On Site Guide where he will see it in black and white:

"Main equipotential bonding conductors are required to connect the following metallic parts to the main earthing terminal:

1) metal water service pipes 2) metal gas installation pipes 3) other metal service pipes ... and ducting ... 4) metal central heating and air conditioning systems 5) exposed metallic structural parts of the building 6) lightning protection systems"

(Yup, lightning conductors again !)