A report on a house I'm buying says there "is no evidence of equipotential earth bonding" of the incoming gas supply to the boiler. I have also been told it needs an electrician to correct this.
What exactly does equipotential earth bonding mean, and how important is it to have it?
It is a cross earthling of metal objects (pipes in this example)
At the boiler, all the pipes should be connected to each other with earth cables and clamps, then at lease a 10mm cable sent back to the main earth terminal (in or near the consumer unit). By what you have posted, it looks like the gas pipe has been left out of this (It is very easy to rectify with an earth clamp and a piece of 10mm earth cable).
Is for how important, it is required by the regs, but hasn't always been.
Sparks...
Its trivial, and is not needed on existing house wiring. If you rewired the place, you would be required to put it in as part of the rewire, but not otherwise. Its safety value is miniscule, but not quite zero. It could save your life, but is unlikely to in the extreme. The majority of houses today dont have equi. Your stairs are 100s of times more risk, and ditto many other things.
Anyone that tells you you need an electrician to correct it is wrong on
2 counts. First there is no need or requirement to fit it, 2nd its an easy diy job.Surveyors use the presence or absence of equipotential bonding as a quick marker of how old the wiring is. If theres no equi, they dont know what age the wiring is, but it wont have been done recently.
NT
Out of interest what reqstates the above??
But can you DIY it under Part P without a building notice?
Yes, it's not notifiable work.
547-02 covers most of it including table 54H. On Site Guide fills in the gaps
Can I refer you all to OSG (brown Cover) Page 25 Section 4.5, no mention there of the need for supplementary bonding of a boiler unless it is in a special location.
What I beleive from the OP is that the main bond is missing and should be connected within 600mm o the entry of the gas supply to the property.
The is no reason or reg that says, that I am aware of, that you must cross bond a boiler.
If some one can point me to it the I will stand corrected.
I'm not with you. 547-02 is the reg that covers it. There is a great deal in the regs that don't appear in the OSG hence the difference in the size of the two volumes.
No it does not 547-02 covers main equipotentil bonding condustors, not cross bonding at boilers. A with regard to a great deal in the regs I have BS7671 in front of me, as is the OSG and all the guidance notes plus other forms of reference.
So at the moment I am still of the opinion you do not need to bond the boiler.
Interesting one this. The more relevant regulation is actually
413-02-02 which contains a (non-exhaustive) list of extraneous-conductive-parts which should be main-bonded. This does include "central heating and air conditioning systems." However remember the definition of "extraneous-conductive-part" i.e. a conductive part which is not part of the electrical installation and which is liable to introduce a potential (generally earth potential).Now a boiler is /inter alia/ an electrical appliance so cannot be "extraneous" - it's an exposed conductive part and needs to be earthed though its CPC (obviously). If installed in a bathroom (or other special location) it would need to be included in the supplementary bonding. Otherwise the boiler /per se/ surely doesn't need bonding.
Whether other parts of the CH system need main bonding is a moot point. If the system involved pipework coming in from outside the equipotential zone (e.g. district heating) then that would certainly need main-bonding. Otherwise, for a regular domestic CH system, there's not really anything to import a potential, so it's outside the scope of the definition. Or perhaps you can argue that the main water bond does the job - especially as it is common practice to supplementarily cross-bond every pipe in sight near a boiler or in an airing cupboard. As has been said, this is not really discussed in the OSG, or the EGBR (other than re-stating the list from 413-02-02), and if it was seen as an 'issue' it would be.
Interesting to note that a similar debate appears to have raged on the IEE Web forum earlier this year:
I wonder what the NICEIC technical manual has to say about this. Anyone out there got a copy?
On Tue, 15 Nov 2005 17:44:46 GMT someone who may be "Stephen Dawson" wrote this:-
Going back to the original posting, 'A report on a house I'm buying says there "is no evidence of equipotential earth bonding" of the incoming gas supply to the boiler.' and that is what the subsequent discussion has been about. I think posters have been saying much the same thing, but in different ways and this is where the confusion arises.
The flow and return pipes of the heating system should certainly be bonded, along with the gas pipe by the meter, under regulations given earlier. If the boiler is joined to these pipes by reliable metal to metal contact then it is bonded, just like the radiators. There is normally no need to attach a bonding conductor to the boiler itself. As an item of fixed equipment it also has the protective conductor from the supply connected to the metalwork of the boiler, just like a built in oven.
Someone asked if this is important. Plumbers are occasionally killed by unearthed pipework that has become live for some reason, such as the heat from a heating pipe slowly melting the insulation of a cable laid over it without protection.
supposed to make a connection? There appears to be no tag of any sort for this purpose.
Is it OK to rely on the pipes to make the connection for a towel rail? I'll need to jumper around some plastic push fit.
MBQ
On 16 Nov 2005 06:04:10 -0800 someone who may be snipped-for-privacy@hotmail.com wrote this:-
Drill a hole in a suitable place, like one of the feet. Tap the hole. Insert bolt.
Does it have an electric heating element?
Plastic feet ;-( only the bath is metal and I'm not drilling a hole in that!
No, it's part of the central heating, hence the reference to pipes.
It's connected by pushfit so I assume I need to jumper around those but I can do that unobtusively if I can rely on the last few inches of copper pipe. Hence my question if you shouldn't rely on the pipes to a bath, how can you rely on the pipes to anything else?
MBQ
On 16 Nov 2005 08:28:28 -0800 someone who may be snipped-for-privacy@hotmail.com wrote this:-
Does the bath have a suitable unobtrusive place to drill a hole?
Some towel rails have an electric heating element, in addition to being heated by water from the boiler. As it doesn't then I would treat it like a radiator, supplementary bonding to the flow and return pipes nearby is usually adequate. I say usually as I can't remotely measure things in the room.
Washers underneath the taps may well insulate the pipes/taps from the bath and thus the bath would be unearthed while the pipes are, which would be potentially dangerous. With a towel rail or radiator there will normally be reliable metal to metal contact between the fitting and the flow/return pipes. If plumbing joints could not be relied upon then every length of pipe and radiator would end up being bonded, which would be ridiculous (but a good source of income for some).
Note, all the above relates to "real" plumbing systems with metal pipes and proper joints. Pushfit "joints" and/or plastic pipes make things more interesting, more difficult in some ways, easier in others.
Ok if you say so. On you go then.
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