To me the risks outweigh the benefits, but then what do I know? Reply to Tony C. Notify me about replies to my post Post Reply.
Its all to do with make sure everything is at the same potential voltage Take for example if the house was earthed through the cold water system and there was a short onto the hot water pipe. This would potential put the hot pipe at a different potential to the cold. You then touch the pipe and the little electrons say - hmm easier to go through you than the pipes - ZAP That's why all pipes in a house should be bonded - and this is typically done as close to the point they might be touched as possible e.
The cross bonding under the boiler should connect all pipework and be done in 4mm bonding. As your new bath is not connected to anything electrical or to any metal which is connected to anything electrical you must not earth it bond it unnecessarily.
Think of it as a metal door handle or a metal knife and fork. It cannot become live nor provide a path to earth. The RCD will not trip as there is no current flow even though the voltage on the earth has now risen and has potential. But if a second fault occurs there is potential for an electrocution to occur. There are a lot of scenarios where this could occur. Where hot and cold water pipes are electrically connected, you need only one bonding jumper — to either the cold- or hot-water pipe.
Otherwise, use a single bonding jumper sized per Building or structure supplied by a feeder. Green and Yellow wires are Earth wires. They are there to prevent anyone getting a shock if the pipes accidentally come in contact with a live supply. You will probably find similar wires on the taps in your bathroom. When you touch the tap, and your feet are on the ground, you complete the circuit, so electricity can flow through you and you experience the electric shock. Bonding is essential for your gas and water installation pipes that connect your home with the Earth Terminal in or adjacent to your consumer unit.
There is no requirement for bonding a boiler; it is earthed. Supplementary bonding is not required in a kitchen. Take for example an earthed appliance such as a kettle on the worktop next to a metal kitchen sink with metal plumbing connected to a buried metal cold water main as illustrated in Figure 1. The kitchen sink and taps are likely to be at Earth potential, i.
Without any protective bonding, if there was a fault with the kettle and a person had one hand on the sink when they grabbed the kettle, itself in a fault condition, then a potential difference will be present across the person leading to an electric shock.
If the water pipe is connected to the main earthing terminal to which the case of the kettle is also connected then the two are effectively joined together and the potential difference between them will be negligible and the shock risk will be mitigated. It also follows from this that the extraneous-conductive-part must be accessible and that it is possible for someone to be in contact with it and a part of the electrical installation under fault conditions.
If the conductive part is inaccessible and will be for the life of the installation and there is no opportunity for simultaneous contact, then it may not be part of the electrical installation and hence not an extraneous-conductive-part. Guidance Note 8 details some simple continuity tests that can be conducted to check whether a part is extraneous or not, depending on the protection installed in the installation. Figure 1 shows an inappropriate application of this requirement. Within your kitchen sink are a variety of pipes.
If these are made of metal, such as cast iron or copper, then the possibility exists that electrical charges could be directed into your home through your sink. These electrical charges could lead to severe injury depending on the extent of the electrical power.
Most sources of electrical charges as associated with the sink come from either static electricity or lightning strikes in a storm. Thus, with some kitchen setups, to reduce the risk of potential electrical shock, your plumber will opt to earth the sink.
This simply means redirecting these electrical charges to the ground from your home. This would be grounded due to the length of the pipes. Even though they attach to your kitchen sink, most water pipes can go several feet past their original point of installation. These days, plumbers have moved away from using cast iron and copper pipes, as well as other metal alternatives.
Polyvinyl chloride, more commonly referred to as PVC, has replaced most of this metal. Instead of using earthing or grounding exclusively, plumbers have also since switched to favoring dielectric unions as necessary.
With a dielectric union, electrolysis rates are reduced through connecting pipes of two materials.
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