Earth for gas meter question

[EFLImpudence]

544.1.2 The main equipotential bonding connection to any gas, water or other service shall be made as near as practicable to the point of entry of that service into the premises. Where there is an insulating section or insert at that point, or there is a meter, the connection shall be made to the consumer's hard metal pipework and before any branch pipework. Where practicable the connection shall be made within 600 mm of the meter outlet union or at the point of entry to the building if the meter is external.

Does that not mean it shall be bonded even if not extraneous?

If so, what do you think is the reason?
If not, what does it mean?

 

[PrenticeBoyofDerry]

I am with EFLI on this.
Regardless of whether or not a liable potential to earth exist, the requirements do state in chapter 54 that a bonding conductor should be connected internally to the metallic pipe work of services even if the service supply pipe is insulated.
Where in the requirements does it say contrary?

 

[bernardgreen]

"The incoming service must be bonded" is probably the simplest fit all statement that removes all abiguity in the mind of the average cable installer. It is a service so bond it simples for all to understand. Even if there is no possibility of the service pipe importing an extranuous voltage it better to say bond it to remove the need for thinking in the mind of the average installer. Of course it was necessary to add " the bond must be to the metal pipe if there is an insulating section " otherwise ( as has been seen ) the bond would be on the plastic section of pipe.

For the many electricians who can think and apply common sense the rules about bonding services bought in via non conductive pipes are questionable.

It might get complicated, I have heard talk that ensuring the safety of gas meter readers may lead to a requirement that an insulating section of plastic pipe is to be fitted between bonded pipe work inside the house and the meter when the meter is outside and accessable by someone standing on the ground but outside the equi-potential zone that is at the potential of the neutral of the electrical supply network.

Rules are rules but often over look common sense when trying to be a one rule for all situations.

 

[GaryMo]

I stand by a plastic gas pipe not introducing a potential from outside of the equipotential zone though the same may not be true for water. Obviously it's to be confirmed by measurement.
If the reason for bonding internally is to keep internal services at the same potential then surely that's supplementary bonding and not main equipotential bonding?

 

[GaryMo]

Have a look at this PDF - http://www.eca.co.uk/filelibrary/download/?FileID=1284

Specifically Page 3.....

Requirements for Main Protective Bonding Conductors

What is Main Protective Bonding?

Main protective equipotential bonding connects the main earthing terminal with the following extraneous-conductive-parts (Regulation 413.3.1.2):

(i) Water installation pipes
(ii) Gas installation pipes
(iii) Other installation pipes e.g. oil, compressed air-lines and ducting
(iv) Central heating and air conditioning systems
(v) Exposed metallic structural parts of the building
(vi) The lightning protection system where required in accordance with BS EN 62305

Note:

1) Incoming plastic gas and water services pipes do not require bonding
2) Where an installation serves more than one building the requirements shall be applied to each building
3) The above list is not exhaustive

We're with the ECA so that's pretty good for me!
Obviously the regulation number stated is out of date (BS7671:2008) but the wordings and meanings still stand.

 

[bernardgreen]

though the same may may [ not ? ] be true for water.

It is odd that one metre of plastic water pipe is deemed ( by regulations ) to be an adequate means to provide isolation between two separate equi-potential zones yet a couple of metres of damp wall can carry enough current to trip a 100 mA RCD.

Tap water is conductive, the amount of conductance depends of how hard the water is and what chemicals have been added at the water treatment works.

So how do the regulations ensure the outside water tap is always going to be safe to touch if it is bonded to the incoming supply neutral. One metre of plastic pipe and the tap bonded to an earth rod ?. That would seem to be the necessity as regulations seem to require ( or at least highly recommend ) that PME "earths" are not exported outside the equi-potential zone to locations where a person can make simultanuous contact between the PME "earth" and ground. "Earthing" an electric lawn mower is now considered dangerous due the possible fault ( lost incoming neutral ) that would take the PME "earth" up to 230 volts.

 

[GaryMo]

though the same may may [ not ? ] be true for water.

Yes, may not.

 

[bernardgreen]

Interesting that the ECA recommends a 20 ohm earth mat being connected to the main "earth" terminal when the electrics in the vicinity of a swimming pool are fed by a TN-C-S supply. Yet connecting an earth rod to the MET is (apparently) frowned upon in a normal domestic situation.

Does the mat bring the ground to the neutral potential ( the whole garden becomes part of the equi-potential zone ) or does it pull the neutral down to ground what ever faults there are in the network ?. Either way it would seem to reduce the hazards around the pool.

 

[PrenticeBoyofDerry]

Requirement 411.3.1.2:
Does not state

Note:

1) Incoming plastic gas and water services pipes do not require bonding
2) Where an installation serves more than one building the requirements shall be applied to each building
3) The above list is not exhaustive

It directs you to chapter 54

 

[GaryMo]

Well, it comes down to how you interpret BS7671 and how capable your are of thinking logically. The ECA document would have been written, had input from and have been approved by many electrical engineers who know a damn site more than you or I.

 

[donrkebab]

There should not be any plastic gas pipes entering any building, or running inside any building, in the uk.

I'm very surprised you blokes don't know this.

 

[PrenticeBoyofDerry]

There should not be any plastic gas pipes entering any building, or running inside any building, in the uk.

I'm very surprised you blokes don't know this.

They do run external service gas pipes in non-metallic materials(Polyethylene) to avoid corrosion. Do they not?
Internally I would not expect plastic pipes on gas services.

 

[PrenticeBoyofDerry]

delete

 

[PrenticeBoyofDerry]

delete

 

[donrkebab]

There should not be any plastic gas pipes entering any building, or running inside any building, in the uk.

I'm very surprised you blokes don't know this.

They do run external service gas pipes in non-metallic materials(Polyethylene) to avoid corrosion. Do they not?

Yes they do , but whats that got do with bonding inside buildings.

Internally I would not expect plastic pipes on gas services.

But in earlier posts all the contributors to this thread including yourself are assuming that plastic gas mains can enter buildings, they do not and never have done. They always change to steel before entering the building thats why main bonding is required - they are extraeneous conductive parts.