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Main Protective Bonding to incoming Gas and Water services

Hello,

My query is in reference to regulation 411.3.1.2. 

It is in relation to a project where we have a block of flats where we have a new proposed pumped water supply and an existing Gas supply both either sleeved or installed in poly existing the ground externally to the building. This is then connected to steel/copper pipework run externally up the outside of the block spurring off at each level into domestic properties. Where the meter is located and then onto the domestic installation.

There is a difference in opinion between Client and Contractor parties in relation to the need to bond these pipes after the meter/stopcock positions. The Contractor is disputing the need to install equipotential protective bonding at the point of entry (after the meter/stopcock) within each domestic property, as they believe that because the pipework coming out the ground is not extraneous material, they don’t have to bond it.

The Consultant designing and tendering the project neglected to provide any instruction either way.

The other interpretation sits around the specific words “entering the building” and “at their point of entry” within Regulation 411.3.1.2, which could be considered to be in line with each flat being its own “equipotential zone”, and therefore individual buildings, and that there is a possibility of exporting a potential from one flat into another flat, if those installations are not fully installed to recent versions BS7671, which in this case is very likely, as there are a significant number of leasehold properties within the blocks where most of the electrical installations within, date back to the 1960/70’s. There is also the fact that within most of the properties main protective bonding is already in place (apart from the new water supply).

Any assistance is appreciated.

Parents
  • The consideration is "where could an extraneous potential come from, as there are no extraneous parts" from your own definition? Extra bonding is not required, but its presence is not a problem. All of the earthing systems in the block are connected anyway, so there is no risk to anyone. This is why the regulation says "external to the building" not any other definition. The situation is in no way dangerous, any more than touching the building walls, etc. In some cases, bonding gives extra risk, as all the bonded metallic parts are raised in potential during an Earth fault, and the disconnection time may be 5 seconds if this is on a distribution circuit. The client should be referred to the big brown book! ( or the blue or yellow ones!).

Reply
  • The consideration is "where could an extraneous potential come from, as there are no extraneous parts" from your own definition? Extra bonding is not required, but its presence is not a problem. All of the earthing systems in the block are connected anyway, so there is no risk to anyone. This is why the regulation says "external to the building" not any other definition. The situation is in no way dangerous, any more than touching the building walls, etc. In some cases, bonding gives extra risk, as all the bonded metallic parts are raised in potential during an Earth fault, and the disconnection time may be 5 seconds if this is on a distribution circuit. The client should be referred to the big brown book! ( or the blue or yellow ones!).

Children
  • Hello David,

    Thank you for your swift response.

    It's just clarifying that an existing (and new)service pipework exiting the ground outside the building in Poly, jointed to metallic pipework, is considered in this case as "entering" the building at that specific point, and not as it "enters" each domestic property (which serves copper pipework throughout each domestic installation). 

    I'm if bonding is not installed, I'm sure The Client will receive annual Gas safety Certificates identifying the absence of Main Protective Bonding to the Gas service within the domestic property, as a defect?