Correct, but as the heating is gas fired and the heat transfer medium is water it shows that the internal water system is in all probability in contact with the general mass of earth. So all the bonding needs to be in place
Earth Bonding trouble
- Thread starter Coaster
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True, but I don't think for the reason being discussed - I suspect that is there to cater for situations in which 'centralised' central heating (e.g. in a block of flats) resulted in pipes entering the premises as e-c-ps.
As I wrote to westie, if one is going to postulate that, say, a concrete floor is sufficiently conductive to provide a 'relevant' path to earth for embedded pipes, then one has theoretically invoked the near-impossible task (in an existing building) of having to 'bond' the entire floor (which is, under those circumstances, an e-c-p)!
Kind Regards, John.
If it is a reinforced concrete floor you do have to bond it!
I don't doubt it - that's the same as my concerns about exported TN-C-S earths to outbuildings with potentially conductive floors in contact with the underling 'earth'. [of course, if I wanted to start a riot, I might point out that, even with a lost supply neutral, they wouldn't get a shock from taps whilst standing on a conductive concrete floor if there were no bonding of the pipework
]However, as I've said, it is to all intents and purposes impossible to bond the entire floor of either a house or an outbuilding - at least, after the floor is in place. I suppose that insulating it would be a more realistic thing to attempt (vinyl flooring should do it!).
Kind Regards, John.
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I don't understand the reason to say that.
Then it will likely be connected via the tank/boiler etc. to the CH main bonding if correctly installed.
Supplementary bonding may be required on the (non CH) water system, but it is not likely.
What I am trying to do is show that in a lot of cases the separate services cannot be looked at in isolation.
So if it appears that the water is by, say, inspection not in contact with earth it probably will be by being connected to other services
So if it appears that the water is by, say, inspection not in contact with earth it probably will be by being connected to other services
They can if they are isolated.
I presume you mean THE earth.
I refer the honourable gentleman to the answer I gave earlier.
P
Paul_C
I think the chances of being able to guarantee that a metallic piping system throughout an entire house is sufficiently isolated from stray earth paths as to be better left unbonded are slim, to put it mildly. When that fact was recognized and the need for bonding understood (and written into the Wiring Regs.) well over half a century ago, I find it rather curious that it can still attract this sort of debate today.
It's presumably likely to become an increasing debate - 'over half a century ago', there were probably no non-metalic service supply pipes; in another half a century or so, there may be few metal ones left.
To mirror your curiosity, I'm also a little curious as to what 'stray earth paths' you are thinking about. If incoming service supply pipes (usually only gas and water, sometimes oil) are either themselves plastic, or include an insulating interuption very close to entry into the premises (as per the OP of this thread), and in the absence of metal waste pipes (which penetrate the earth) connected to metal baths/sinks (and, of course, in the absence of any 'bonding'!), I'm not sure what stray paths to earth you have in mind. All there seems to be is the substance of the building itself and, for a 'conventionally built house', that's extremely unlikely to offer a low enough resistance path to earth to be of any consequence (and, as discussed, if it did, it would somehow have to be bonded!).
You seem to be implying that there is a requirement for main bonding of internal metal pipework, per se, but that surely isn't the case? The only requirement for MPB relates to extraneous-conductive-parts - so if a service pipe enters a property as plastic, or is insulated from the house's metal pipework very soon after entry, I don't think there's anything in the Wiring Regs which actually requires MPB, is there? (but, as I said, try telling that to the (wo)man doing a PIR/EICR!).
Kind Regards, John.
H
holmslaw
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H
holmslaw
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I agree that it doesn't specifically mean 'services entering a building', but nor does it mean "any metalic parts.....". Rather, it means 'any metallic parts inside the building which are not part of the electrical installation and which are 'liable to introduce a potential (generally earth potential'. In practice, that essentially boils down to metallic parts (mainly pipework) in electrical continuity with 'services entering the building' - otherwise it's very hard to see how it can 'introduce a potential'.
That's where people start disagreeing. If the meter were removed there would theoretically be no need for bonding of the house-side pipework.
As I've said before, I was brought up with the adage that "if it's metal, earth it" (which would usually become 'bond it' in terms of the way we now think). However, it is apparent there are now some people who argue that 'unnecessary' connection of metalwork to earth can decrease, rather than increase, safety.
Kind Regards, John.
I've often seen that said, but I've certainly seen a number of premises in which it is not the case.
Kind Regards, John.
Why do you/anyone think they do not? Just interested, not disagreeing.
I presume the point is that I think one would be hard pressed to find anything in the regs which actually says that. The attitude of the regs seems to be that so long as any conductor 'liable to introduce a potential' is bonded close to where it enters a property, then that's all that matters.
I think one of the complications of these discussions is that, by virtue of pumps, motorised valves, immersion heaters, showers etc., domestic pipework is usually in electrical continuity with exposed-conductive-parts (i.e.effectively becomes an extension of those exposed-conductive-parts) - which raises totally different issues from those relating to the main bonding of extraneous-conductive parts. In practice, this may sometime leave uncertainties as to whether a particular bit of G/Y (whatever it's called) should be 10mm² or 4mm² !
I'm inclined to the view that, once one excludes silly (e.g. door knobs) and/or contentious (e.g. metal baths) things, that adage of 'if it's metal, earth/bond it' is probably the common sense approach, certainly for domestic pipework, given the various uncertainties (present or future) which often exist.
Kind Regards, John
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