[Amps] Safety grounding - was Mains Isolation Transformer

[Peter Chadwick]

I missed the message from Jim saying:
>>From my understanding of electrical codes in the UK, what you are
> doing is not only unsafe, it is also illegal. The bond between
> neutral and earth in the UK is made within the mains system, not at
> your premises. Further, it is quite important from a safety point of
> view that all your earth connections be bonded together, NOT
> separated.<<
The neutral is earthed by the electricity supply company on their pole. From that pole, live and neutral are treated as being 'live ' conductors, and are not earthed. UK supply grounds the neutral at multiple places along its run, while certain European countries bond the neutral to ground at each installation. Because I'm not on PME within the house, all the bonded stuff in the house has its own earth. Separation of RF earth from safety earth would only have much validity in the case of a lightning strike, although in fact, they are connected together via the screening  and one conductor of a very heavily armoured 4 core cable, a conductor of 6 inch wide aluminium sheet and numerous coax outers. It was certainly all considered OK by the very qualified electrical contractor who had to do a fair amount of work bringing other parts of the installation up to compliance with the 16th edition of the IEE Wiring Regs. This incidentally, included fitting Residual Current Devices (US English = GFI), which trip off with small amounts of 80 and 160metre RF. A problem yet to be fixed......
The case of PME is a totally different matter, because of the possibility of a ruptured neutral. That's why I refused to have it - the electricity supply people get a bit shocked when you offer to show them the order published by Her Majesty's Stationery Office and signed by Her Majesty's Principal Secretary of State for Energy that says a consumer may refuse to have PME in his installation!
>> It IS entirely correct to treat the neutral as separate from earth.<
That's because it is!!! Much safer, too. However, some outback areas of VK land apparently use (or maybe used) a single wire feed and earth return.....Don't know what the supply regulation is like. 
About 35 years ago, I took a new 2MHz marine transceiver (I'd done the tx design) for a 'first fitting'. The shipyard were supposed to provide a 24v 50 amp supply, but actually fused it at 5 amps. While waiting for them to fix it, the foreman was talking to me. Forgetting his broad Yorkshire accent--
"These 'ere new ships, they've got this 'ere new fangled AC on them. It's like DC, thee has two wires, but they keep turning rahnd!"
A somewhat startling explanation of AC theory....................

73
Peter G3RZP