I used to run old electronic items that had a live or half mains voltage
chassis from an isolation transformer with the chassis locally earthed
independently. OK I know all about the dangers, but I'd suggest they are
much less than running the devices on raw direct mains with no earth at all
if you are leaving it open at the rear.
So without quoting the really obvious pitfalls and breaches of rules in
this, would you also take the chassis to an earthing rod, or to the earth
on the primary side of the transformer?
I don't see any detriment to the mains either way, since the final supply
is isolated and you should be able to earth anything you like as long as the
transformer is good and can isolate as it says on the tin, so to speak, it
certainly has the current capacity, as its bloody heavy!

Brian

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On Wednesday, 9 August 2023 at 12:16:31 UTC+1, Brian Gaff wrote:
> I used to run old electronic items that had a live or half mains voltage
> chassis from an isolation transformer with the chassis locally earthed
> independently. OK I know all about the dangers, but I'd suggest they are
> much less than running the devices on raw direct mains with no earth at all
> if you are leaving it open at the rear.
> So without quoting the really obvious pitfalls and breaches of rules in
> this, would you also take the chassis to an earthing rod, or to the earth
> on the primary side of the transformer?
> I don't see any detriment to the mains either way, since the final supply
> is isolated and you should be able to earth anything you like as long as the
> transformer is good and can isolate as it says on the tin, so to speak, it
> certainly has the current capacity, as its bloody heavy!

Don't earth it at all. That way you could touch anything (apart from the EHT)
without getting a shock apart from perhaps a very slight one from whatever
leakage current there is between primary and secondary windings.

John

>
> Brian
>
> --
>
> --:
> This newsgroup posting comes to you directly from...
> The Sofa of Brian Gaff...
> bri...@blueyonder.co.uk
> Blind user, so no pictures please
> Note this Signature is meaningless.!

Yes but if there are things that generate voltages such as eht for old
analogy crt tellies, you will still get a shock because of the different
voltages. Of course the one hand in your pocket rule is very much in order
in such cases.
Brian

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"John Walliker" <jrwalliker@gmail.com> wrote in message
news:8473faac-8b0f-4d43-ab5e-7f4ffeae600fn@googlegroups.com...
> On Wednesday, 9 August 2023 at 12:16:31 UTC+1, Brian Gaff wrote:
>> I used to run old electronic items that had a live or half mains voltage
>> chassis from an isolation transformer with the chassis locally earthed
>> independently. OK I know all about the dangers, but I'd suggest they are
>> much less than running the devices on raw direct mains with no earth at
>> all
>> if you are leaving it open at the rear.
>> So without quoting the really obvious pitfalls and breaches of rules in
>> this, would you also take the chassis to an earthing rod, or to the earth
>> on the primary side of the transformer?
>> I don't see any detriment to the mains either way, since the final supply
>> is isolated and you should be able to earth anything you like as long as
>> the
>> transformer is good and can isolate as it says on the tin, so to speak,
>> it
>> certainly has the current capacity, as its bloody heavy!
>
> Don't earth it at all. That way you could touch anything (apart from the
> EHT)
> without getting a shock apart from perhaps a very slight one from whatever
> leakage current there is between primary and secondary windings.
>
> John
>
>>
>> Brian
>>
>> --
>>
>> --:
>> This newsgroup posting comes to you directly from...
>> The Sofa of Brian Gaff...
>> bri...@blueyonder.co.uk
>> Blind user, so no pictures please
>> Note this Signature is meaningless.!