Do I fit electrical earth clamps when pipes are hot or cold?

[bernardgreen]

John

The point I was making was that regulations would appear to prohibit any direct connection from a gas pipe or any other extraneous conductive item to the neutral conductor of the installation.

But they insist that a gas pipe or any other extraneous conductive item is connected to the neutral via the MET

( obviously not the case in a TT installation where earth really is an earth at ground potential )

 

[JohnW2]

The point I was making was that regulations would appear to prohibit any direct connection from a gas pipe or any other extraneous conductive item to the neutral conductor of the installation. .... But they insist that a gas pipe or any other extraneous conductive item is connected to the neutral via the MET

To be more correct, the requirement is surely to connect to gas pipe to the MET (hence CPCs and exposed extraneous parts throughout the installation) in order to create an equipotential zone. In terms of bonding (i.e. creation of that equipotential zone), the fact that the MET is also conected to the incoming neutral is irrelevant, and the point of the exercise is not to "connect to the neutral via the MET".

Kind Regards, John

 

[bernardgreen]

the fact that the MET is also conected to the incoming neutral is irrelevant, and the point of the exercise is not to "connect to the neutral via the MET

Is it irrelevant ? It is connecting the metal work to a live conductor. ( we are told for safety reasons to treat the Neutral as a live connductor )

 

[ban-all-sheds]

Can I connect a length of blue wire from the neutral terminal of a ring main socket to the gas meter outside my house. ?

What do the regulations say ?.

They require me to make that connection

They don't require me to make one.

 

[bernardgreen]

They require me to make that connection

They don't require me to make one.

Please do not snip sentences to change the meaning.

I wrote "" They require me to make that connection, only it must be from the MET to the gas pipe and be in green and yellow insulated wire. "" and the MET is connected to the Neutral ( other than in a TT supply )

 

[JohnW2]

the fact that the MET is also conected to the incoming neutral is irrelevant, and the point of the exercise is not to "connect to the neutral via the MET

Is it irrelevant ? It is connecting the metal work to a live conductor. ( we are told for safety reasons to treat the Neutral as a live connductor )

I suppose that this is one area where the difference between earthing and bonding does become important. We create an equipotential zone by ensuring that all CPCs (hence exposed-conductive-parts) and extraneous-conductive-parts are joined (bonded) together, the usual common point of this connection being the MET. From the point-of-view of the equipotential zone, it doesn't matter what else (if anything) the MET is connected to. Indeed, were it not for the fact that the bonding conductors would melt if extraneous-conductive-parts had low impedances to earth, the MET could be connevted to the supply L without the equipotential zone ceasing to be equipotential (i.e. become unsafe).

However, the other function of the CPCs is to facilitate operation of protective devices during fault conditions, and for that purpose (described in the industry as 'earthing') one needs the MET to have a low impedance path back to the transformer neutral. With TN-C-S that connection is, indeed, achieved via the N supply conductor, but with TN-S, there is a separate ('earth') conductor back to the transformer. With TT, it's all a bit moot, since the Ze will generally be too high for OPDs to operate in response to faults - but the path, such as it is, back to transformer neutral is then genuinely via 'the earth'.

Kind Regards, John

 

[RF Lighting]

No, the regulations require you to make a connection between the MET and the gas supply, as they could both be at different potentials simultaneously.

I know you're never going to accept this but there IS a huge difference between earthing an bonding, and just because bonding sometimes happens to be earthed, does not mean that you are earthing a pipe.

 

[JohnW2]

I wrote "" They require me to make that connection, only it must be from the MET to the gas pipe and be in green and yellow insulated wire. "" and the MET is connected to the Neutral ( other than in a TT supply )

You did, indeed. However, that "other than..." should presumably also include TN-S - since, as far as you are concerned, you have to connect the MET to the DNO-supplied 'earth', not the DNO-supplied neutral. The connection to neutral then occurs back at the transformer.

Kind Regards, John

 

[RF Lighting]

A TT supply still requires the MET to be connected back to the transformer star point (neutral) just by a high resistance conductor (the ground)

 

[JohnW2]

A TT supply still requires the MET to be connected back to the transformer star point (neutral) just by a high resistance conductor (the ground)

It does, indeed, but (these days) that's to facilitate operation of an RCD - since, as I said, the Ze will usually be too high for an OPD (even a 5A/6A one) to operate in response to an L-CPC fault. Whether the 'earthing' of a TT installation achieved anything much in the days before VOELCBs and RCDs, I'm not so sure.

Kind Regards, John

 

[RF Lighting]

Oh I agree. I'm just trying to understand bernards paranoia and confusion with reagards to earthing, bonding and neutral. They are each different and perform different duties, it just so happens that they all connect together at some point in the supply network regardless of the supply type.

 

[ban-all-sheds]

Please do not snip sentences to change the meaning.

Please don't write confused nonsense to change meaning.

"" They require me to make that connection, only it must be from the MET to the gas pipe and be in green and yellow insulated wire. ""

There you have it then.

The regulations DO NOT require you to connect the neutral terminal of a ring main socket to the gas meter outside your house.

and the MET is connected to the Neutral

Mine isn't. At least, not anywhere near my house, and I do not have a TT supply.

 

[ban-all-sheds]

I'm just trying to understand bernards paranoia and confusion with reagards to earthing, bonding and neutral.

Repeat after me:

I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.
I will not try to understand bernards paranoia and confusion with regards to earthing, bonding and neutral - that way madness lies.

 

[JohnW2]

Oh I agree. I'm just trying to understand bernards paranoia and confusion with reagards to earthing, bonding and neutral.

I think one of Bernard's main issues is that, even though the concepts and purposes of earthing and bonding are completely different, they are often inseparable, except in terms of the intent of the person who installed it. 'Earthing' is achieved by connecting something (usually indirectly) to the MET (with the purpose of providing a path back to transformer N to facilitate operation of protective devices in the event of an L-CPC fault). If one connects something to the MET with a main bonding conductor (with the purpose of achieving equipotentiality), in addition to the desired 'bonding', one will therefore also have 'earthed' the something. The something may well not need earthing, but it is no less 'earthed' by that conductor than it would be if it had been deliberately and necessarily 'earthed' by connection to CPC/MET.

Kind Regards, John

 

[ban-all-sheds]

EEBADS.

Earthed Equipotential Bonding And....

Earthed, not Earthing