Fuse Box Grounding

[Wooden]

I have just checked the fuse box in my parents pre war house & I have noticed that the earth which was previously attached to the metal gas main pipe has been disconnected. I can only assume that this happened when they had some work done on the meter & pipes 2 years ago. I am now concerned as it appears that the system is not earthed correctly. Where should the main fuse box be earthed to??

Steve

[stefek.zaba]

You're right to be concerned, though the particulars are different to what you seem to expect. The electrical installation has its own earth, which is the 'master' or 'reference' earth - the Electrical section of the uk.d-i-y FAQ (at

goes into the reasoning and nomenclature. But the other incoming services - gas & water - should be electrically bonded to this 'master' earth (so that all of the exposed metalwork in the house which could become live - e.g. gas & water pipes in the presence of a single fault in your boiler/immersion wiring - is at the same potential, and is likely to be at the reference earth potential so that any faults to it will make a fuse blow). And it's this bonding conductor which is disconnected, and should be remade as a matter of mild urgency. There should similarly be a reasonably beefy bonding cable running to where the water service enters the house.

Now, given it's a prewar installation, it's possible - but pretty unlikely - that the incoming gas connection was indeed intended as the main means of earthing. A gen-yoo-ine electrician will do you a full inspection and report on the state of the installation, which will include the earthing arrangements, for about 50 quid; not too silly an amount if you don't feel like getting educated in the inner mysteries of electrons and their habits ;-)

HTH - Stefek

[Lurch]

The chances are on a pre-war house with no updated wiring the main earth will have been the metal service pipes, (gas & water), as they will be effectively 'earthed' underground. With the advent of PVC service pipes the earth is now deemed unsatisfactory by this method and will need to be connected to either an earth terminal provided by the electricity board or a earth rod fitted by yourselves, (or a electrical contractor). If the earth is not connected to anything and nothing has been updated the chances are there are many other things wrong with the installation, pretty much condemnable from my experience. (eg rubber cables, lack of earth in final circuits, no earth bonding etc...) ..

SJW A.C.S. Ltd.