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Re: Earth wires

On Sun, 11 Jan 2009 11:53:47 -0000, "Frank Turner-Smith G3VKI"
<g3vki@turner-smith.co.uk> wrote:
Thanks everyone will try and sort something out from the wide range of
responses.Not sure that I didnt get lost again though
Cheers
Rich
>"Brian Reay" <seewebsite@invalid.com> wrote in message
>news:NYjal.1230$Z_6.923@newsfe25.ams2...
>>
>> "Derek" <invalid@invalid.invalid> wrote in message
>> news:gkcgln$tvu$1@news.motzarella.org...
>> >> If you think you are immune from the PME problem if you've no
"outside
>>>> earth" you clearly don't understand the issues.
>>>
>>> Once again you are shifting your principles to suit the direction
>>> from which the wind is blowing.
>>>
>>> My suggestion was that he should connect his radio to the mains
>>> earth exactly as he proposed. There is no PME problem
>>> with that arrangement, and, indeed, if any person were to raise
>>> the spectre of PME, then such a person would be an idiot. If there was
>>> such a problem, then that problem would apply to any of the
>>> goods sold to the consumer to plug into the mains, goods
>>> such as washing machines.
>>
>>
>> You clearly have no concept of the "PME problem".
>>
>> The issue isn't the appliances inside the house it is the presence of
>> conductors (eg antenna wires or RF earth wires) which are, or may become,
>> in contact with the earth and which come into the house or PME protected
>> environment.
>>
>> If there is a "neutral break", all the appliances, central heating,
>> plumbing, .........  "float" up to mains potential. If there is no
>> connection (eg no wires to real earth), this condition is quite safe. If,
>> however, there is a connection between the outside earth (eg an RF earth
>> or a "drooping" antenna wire) a risk exists.  Even an outside tap can
>> introduce a risk, if the correct precautions are not taken.
>>
>> There are several ways to protect yourself but your suggestion of using
>> the mains earth (without reference to other steps) introduces a risk. In
>> the absence of the preferred solution (bonding of the RF earth to the PME
>> earth) this risk is increased by your approach.
>>
>> Brian
>> www.g8osn.org.uk
>>
>Shortly after we moved into this QTH we noticed "tingles" from the washing
>machine and tumble dryer, both located in a small utility room.
>Investigation showed that the previous owner, a keen but not very good DIY
>enthusiast, had made two fundamental errors when connecting up the ring
>main.
>1. The earth wires at each end of the ring were connected together in the
>consumer unit, but were not connected to ground, so anything connected to
>ring main earth was free to float to any potential!
>2. The ends of the ring main were connected to different circuit breakers,
>so opening one without the other did not isolate the ring! I assume this
>also meant the ring was limited to 60 instead of 30 Amps!
>Not exactly a PME problem I suppose, more of a PRAT problem.

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