Query from the Combustion Chamber......................
- Thread starter FiremanT
- Start date
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I'm talking about a MET which consists of an exposed earth block (rather than using a CU earth bar as the MET). It will usually be close to the CU (hence usually close to the meter and cutout). However, it's not unusual for gas and/or water services to enter in that vicinity, and quite common for gas meters to also be very close. Such a MET is therefore often in a general area where plumbers may well 'play'.
Knowing whether a plumber would ever consider disconnecting MPB conductor(s) from that nearby MET rather than from nearby pipe(s) it/they went to requires an understanding of how plumbers's minds work - and is not a question I could answer. However, it could certainly be done very easily by anyone with a screwdriver.
Kind Regards, John
It would be, but that EICR might not take place until a good few years after the plumber had disconnected it.
Kind Regards, John
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Wow! Who would have thought sparks disagreed with each other as much as plumbers and gasmen 
What is a MET? I assume it is a * Earth terminal ?
The OP was asking if it is okay to run the bonding INSIDE the oil line, and was worried about degradation of the insulant. My thought was why should it.
What is a MET? I assume it is a * Earth terminal ?
The OP was asking if it is okay to run the bonding INSIDE the oil line, and was worried about degradation of the insulant. My thought was why should it.
MET is the main earthing terminal, usually a block of metal with two screws per terminal which all of the main protective bonding, the earthing conductor whether it be an earth rod or a suppliers earth and all of the building Circuit protective conductors connect to. The earth rail in a consumer unit may be used for a MET instead.
I'd say no to using the oil pipe as a conduit as there may be residue in them. I don't know how heavy oil would react with it, nor how it would react to the cable becoming heated in a network fault scenario (albeit very rare).
I'd say no to using the oil pipe as a conduit as there may be residue in them. I don't know how heavy oil would react with it, nor how it would react to the cable becoming heated in a network fault scenario (albeit very rare).
If it were possible to get a cable/wire/whatever all the way through the old oil line (which I personally very much doubt), then it would presumably be possible to pull things through (e.g. small pieces of rag) and remove all but the slightest (and, I would say, irrelevant) residues of oil. I can't see that degredation of the insulaltion of the bonding conductor, even if it happened, would matter, and nor do I think that very slight traces of oil (after 'internal wiping') would be an issue in the (as you say, very rare) eventuality that the conductor getting extremely hot.
However, as I say, I suspect this is probably all moot, because I very much doubt they'd be able to get anything through the ('ex') oil line.
Kind Regards, John
I'd say join to the water MPB (main protective bonding) as stated on page 1 by lec //www.diynot.com/forums/electrics/query-from-the-combustion-chamber.371671/#2833052
My preferred choice anyway.
My preferred choice anyway.
Discussions in forums like this have a habit of taking on a life of their own. ... It's all very well having all this discussion about how best to loop bonding between gas and water services, but no-one has yet actually given us any reason to believe that the water service is actually bonded anywhere near where the gas service now needs bonding.
I somewhat suspect that such may not be the case - hence the question about using the old oil line (if there is one - I haven't even seen confirmation of that!) as a conduit.
Kind Regards, John.
I don't think it did - at least, not clearly. As well as asking about the using the old oil line as a conduit, the OP also asked if the gas service could be bonded to the "already earthed mains water". EFLI replied that such would be fine, but I then pointed out that I had interpreted the question as relating to bonding to a water pipe (which itself was bonded elsewhere), rather than to extending the water service's bonding conductor.
We do not appear to have subsequently received any clarification about this - and the fact that the OP has recently made further comments about use of the old oil line (which, at the very least, would be a much more fiddly approach if there were a water service bonding point nearby) makes me wonder.
Kind Regards, John
The above is the post that originated in the CC. I may not have been totally clear, so I apologise for that. Of ourse, you cannot see the responses in the CC, so having the link confused the issue somewhat, but it is automatically generated, - I should have deleted it. It is generally accepted, as a gas fitter, that one cannot link a bond from a gas pipe to an existing bonding clamp on a water pipe, as we believe that the cable has to be a continuous length, and this is obviously not possible as a retro fit. Posts here seem to contradict that widely held belief, which s interesting in itself.
The guy that posted this wanted to use the oil line as a conduit, rather than a bonding in itself.
Another suggestion raised in the CC was to use an earth spike. This was generally seen as non conforming, buy IS it?
I am not the original OP.
Looping from an existing water bond is fine. It is preferable to keep the bonding cable unbroken when ever possible, but there is no regulation which prescribes this.
I also see no real issue with using the old oil line. I'd like to see it cleaned out first just to minimise the risk of any damage to the wire insulation, but other than that I'd be happy to do so.
As for using an earth spike, absoloutley 100% never, not even in a million years.
Earth spikes are used for earthing. You are wanting to bond the gas. Earthing and bonding are two entirely different things, and installed for completely different reasons.
Connecting an earth spike woull acheive nothing at all. It may even make the overall installation LESS safe than leaving it unbonded. (Which you must not do)
I also see no real issue with using the old oil line. I'd like to see it cleaned out first just to minimise the risk of any damage to the wire insulation, but other than that I'd be happy to do so.
As for using an earth spike, absoloutley 100% never, not even in a million years.
Earth spikes are used for earthing. You are wanting to bond the gas. Earthing and bonding are two entirely different things, and installed for completely different reasons.
Connecting an earth spike woull acheive nothing at all. It may even make the overall installation LESS safe than leaving it unbonded. (Which you must not do)
Right. Thanks for clarifying. As you will have seen, 'linking a bonding conductor from the bonding clamp on one service to bond another service is allowed. Given the varying opinions about the best/acceptable way to do that, the method most likely to be acceptable to everyone would be to use a new continuous piece of cable to link the two clamps (on on gas, one on water) and to carry that new cable (again, 'continuously') and join it to the existing bonding cable (ideally with a crimped joint).
Ah, right. I misunderstood. I thought that second little paragraph was a response from someone, suggesting that there might be a redundant oil line which could be used as a conduit for a bonding conductor. I still think that's a theoretical possibilty (if one cleaned out the pipe first), but doubt you'd get the cable through it. We understood that the suggestion was to use the oil line as a conduit - the theoretical possibility of possibly using the oil line itself as a conductor was introduced (and essentially dismissed) by 'us' - sorry if that caused any confusion.
That would not fulfil the purpose of main protective bonding, which is to connect the incoming service pipe to the electrical installation's Main Earthing Terminal (MET), to ensure that significant/dangerous voltage differences cannot exist between them.
Kind Regards, John
An earth spike is NOT the answer. The cable is a bond and NOT an earth. The purpose of a bond is to ensure all exposed metal work inside the building is at the same potential. This ensures anyone touching two bits of metal will not get a shock from them being at diffferent voltages.
The "earth" in a PME system is not true earth ( ground ) as a earth spike is but is instead the same potential as the neutral from which is it derived at the cut out ( main fuse before the meter ). In the event of a fault in the network ( broken neutral ) the earth in the house could become many volts above ground. So "earthing" some pipes to a ground spike would increase the risk of electrical shock during a network fault.
If all metal is bonded to the "earth" ( the neutral potential ) there is no hazard to people inside the house as all metal is at the same voltage. It may be 230 volts above true ground but as long as no one touches true ground ( or anything in contact with ground ) and the "earth" at the dame time then they are safe.. Birds perching on 11,000 volt overhead lines are safe and comfortable as long as they touch nothing else.
I know someone who got a phone cable through a redundant small bore copper pipe for about 20 yards. Using a powerful vacuum cleaner to pull a light wieght draw cord, that to pull fishing line and that to pull the phone cable. Because of the reduced air flow the vacuum cleaner may over heat if run for a long time.
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