I have seen many a post asking if it is acceptable to use a single MEB conductor for all services providing it is unbroken. My question is: Is there a regulation that prohibits the use of a single conductor for earthing and bonding of a TT installation providing it is unbroken?
Hypothetical question
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Doc Hudson
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Earthing and bonding are two different things, I presume you are referring to bonding not earthing?
Doc H.
Doc H.
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OK,
first of, there is NO such thing as a MAIN earthing conductor (not in a normal installation anyway),
secondly, NO, it is NOT permissable to use the earthing conductor for the main earth bonding conductor, there would be no way of testing Ra or continuity of main bonds satisfactorily without substantial dismantling of the installation,
thereby contravening the regs regarding maintenance and testing accessibility, IMHO.
first of, there is NO such thing as a MAIN earthing conductor (not in a normal installation anyway),
secondly, NO, it is NOT permissable to use the earthing conductor for the main earth bonding conductor, there would be no way of testing Ra or continuity of main bonds satisfactorily without substantial dismantling of the installation,
thereby contravening the regs regarding maintenance and testing accessibility, IMHO.
As Steps and the Doc say, earthing is earthing and bonding is bonding .
Yes you can use a single bonding conductor ,say, to the gas and then the water, cable remains uncut at the gas.
Cable to an earth rod is dedicated.
Yes you can use a single bonding conductor ,say, to the gas and then the water, cable remains uncut at the gas.
Cable to an earth rod is dedicated.
To be honest, the 17th has some new terminology that that tends to throw some . Goalposts keep being moved. One of the most ridiculous came in with the 16th , where the voltage ranges were altered from low, medium & high .
In todays range how the hell can up to 1000 volts be in the Low range. The word "low " suggests a safe voltage .
In todays range how the hell can up to 1000 volts be in the Low range. The word "low " suggests a safe voltage .
But could you go on from the rod to the water service,,, if there are no other extraneous services at all??
Then the rod clamp would essentially become the MET?
Then the rod clamp would essentially become the MET?
NO,
not IMHO anyway,
how would you test continuity of MEBs?
remember, you have to allow for maintenance and testing, without the disruption of dis-mantling.
to test MEB you would have to remove the earthing conductor also,
to test Ze/Ra you would also have to remove the MEB,
if you want to use the rod terminal as MET are you going to extend all your CPCs to this point?
not IMHO anyway,
how would you test continuity of MEBs?
remember, you have to allow for maintenance and testing, without the disruption of dis-mantling.
to test MEB you would have to remove the earthing conductor also,
to test Ze/Ra you would also have to remove the MEB,
if you want to use the rod terminal as MET are you going to extend all your CPCs to this point?
thats going to be a major problem if you install a submain then, running each CPC all the way back to MET...
So then,,,, not much different to using an earth block then?
you can chose where to install your MET,
this is (normally) where you will terminate your earthing conductor , MEBs , and CPCs , unless you can provide a good design criteria as to why you have deviated, or designed in some other manner perhaps,
entirely up to you, as the designer to how you comply with 7671, and other accepted practises, such as good workmanship and systems deemed as being of acceptable of a competent person by your peers.
---------- Post Auto-Merged at 20:24 ---------- Previous post was made at 20:22 ----------
this is (normally) where you will terminate your earthing conductor , MEBs , and CPCs , unless you can provide a good design criteria as to why you have deviated, or designed in some other manner perhaps,
entirely up to you, as the designer to how you comply with 7671, and other accepted practises, such as good workmanship and systems deemed as being of acceptable of a competent person by your peers.
---------- Post Auto-Merged at 20:24 ---------- Previous post was made at 20:22 ----------
what part are you referring to Noz?So then,,,, not much different to using an earth block then?
The way you'd test it mate?
Although I agree that you'd have to disconnect and reconnect the earthing conductor inbetween some of the steps,,, which might seem a bit odd.... However as the only "live" test is for Ra it isn't that disruptive or difficult to do when the rod connection is accessible (which it should be anyway)
Although I agree that you'd have to disconnect and reconnect the earthing conductor inbetween some of the steps,,, which might seem a bit odd.... However as the only "live" test is for Ra it isn't that disruptive or difficult to do when the rod connection is accessible (which it should be anyway
)
Ra is tested DEAD,with MEBs disconnected too,
Ze is tested live with MEBs disconnected,
MEB continuity is tested dead with MEB disconnected,
how would you know what to disconnect where though?
Ze is tested live with MEBs disconnected,
MEB continuity is tested dead with MEB disconnected,
how would you know what to disconnect where though?
I don't think its the best idea to start looping bonding conductors from earth rods TBH . If I came upon a second cable connected to a rod I'd assume it went to a second rod not the water . Carp idea IMHO.
We are talking hypothetically guys
I'm not too keen on the idea either, but if labeled up fully and correctly then there wouldn't be any ambiguity
I'm not too keen on the idea either, but if labeled up fully and correctly then there wouldn't be any ambiguity
i have done this before. there was already a 10mm to water (no gas). getting a new cable to rod was impractical, so earth from water (1/2m away) was extended to earth rod. everything labelled, note on inside cover of CU (since paperwork will never be there for next person), along with note on certs
[quote name='Andy
damn. should i arrange to go back and swap it round?!
Too right you should,,, I'm suprised that everyone who's been in there isn't dead already ; )
; )
