Domestic electrical continuity question

[mail]

I've just fitted a new light into an existing circuit - I did some coninuity testing to make sure I had good connections and earth connectivity, and discovered that I also have some continuity between earth and neutral. What I'm actually finding with my =A39.99 from B&Q tester is that on earth I have full continuity and a good strong buzz, but between earth and neutral I have a broken but regular buzz, almost as if its oscillating if that makes any sense. What I also notice is that if I turn off the mains switchh on the consumer unit, as opposed to just the MCB on the circuit I'm working on, the continuity disappears. I'm not an expert and don't want to get into dangerous areas beyond my knowledge - can someon advise if this is normal or if I have a problem I should be concerned about. I read somewhere else that there is usually a connection between earth and neutral in a modern consumer unit. That doesn't make sense to me intuitively, it sounds dangerous, but then I'm not an electrical engineer. Any advice gratefully received.

R=2E

[Owain]

This /may/ indicate a high resistance connection

The MCB is a single pole switch and does not disconnect the neutral

There is often a connection between the neutral and the earth in the supplier's service fuse box, to provide the Protective Multiple Earth (PME) - see the UKDIY FAQ for earthing systems. If you are PME then you should have a good solid connection between neutral and earth with the main switch on, not a flakey one.

Otherwise the neutral should be at approximately the same potential as The General Mass Of Earth, this is why we usually can use single-pole fusing; double-pole fusing was used until about the 1950s when the supply was floating with neither wire tied to eart.

Owain

[Bob Minchin]

R.

Perfectly OK. Various earthing systems are used in UK but all keep the neutral relatively close to earth potential.

Bob

[Lurch]

On 26 Feb 2007 11:40:57 -0800, [e-mail] mused:

Maybe you shouldn't have started the job then?

Depends on the earthing arrangements on the supply. On some supply types neutral and earth are connected in the service head.

[Tony Williams]

Switch your £9.99 to AC voltage and measure N-E. Any voltage there (even a small one) can upset the functioning of the (DC) Ohms range.... might even damage it sometimes.

Our N-E voltage is about 0.6Vac but I have seen a posting here where someone claimed over 10Vac.