brucew268

Mains shield earthing?

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You can buy proper screened mains cable - we use it for some things at work. However, it;'s really not necessary, unless your mains cable is 40 feet long and happens to run right through the middle of a giant switch-mode PSU!

If you must use it, as said above, connect the screen at both ends and only ever use it IN ADDITION to the main earth core of the cable.

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if you are talking about this stuff   https://www.tlc-direct.co.uk/Products/MF2dot5slash3.html?source=adwords&ad_position=1o4&ad_id=45425533757&placement=&kw=&network=g&matchtype=&ad_type=pla&product_id=MF2.5%2F3&product_partition_id=174055352947&version=finalurl_v3&gclid=CjwKCAjwuO3cBRAyEiwAzOxKsvhqrjC7oU67szvgDCdqXIOq8qH5kxbl9q2woJVlubuBcRJ_GbUFxhoCvmkQAvD_BwE

I used it, or something very similar for some mains leads a while back, when we had a dog who  decided chewing mains cable was a good idea. I am in no way qualified to arse about with mains power, but seem to remember checking at the time and being told the screen or shield or whatever it's called was not designed to be connected to anything. It was there simply for strength. In fact I seem to remember being told it should not be connected, as it didn't have the required insulation around it, and if the plastic outer was damaged in any way it could cause problems.

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I've used shielded mains many times fitting NACOS approved alarms, but that's generally armoured cable. What Dudy says above is corrected the crappy foil shields aren't intended to carry mains voltages and aren't necessarily insulated according to regs. There's no point to use it, and it's not something you should fit yourself.

To be fair this should be beyond the scope of discussion here based on the forum electrical safety rules. Not sure why this thread has been allowed to run assuming the rule applies equally to every thread starter.

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On 14/09/2018 at 17:48, Beobloke said:

You can buy proper screened mains cable - we use it for some things at work. However, it;'s really not necessary, unless your mains cable is 40 feet long and happens to run right through the middle of a giant switch-mode PSU!

If you must use it, as said above, connect the screen at both ends and only ever use it IN ADDITION to the main earth core of the cable.

Sounds like an interesting project.O.o

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Super Wammer
On 15/09/2018 at 14:53, sq225917 said:

I've used shielded mains many times fitting NACOS approved alarms, but that's generally armoured cable. What Dudy says above is corrected the crappy foil shields aren't intended to carry mains voltages and aren't necessarily insulated according to regs. There's no point to use it, and it's not something you should fit yourself.

To be fair this should be beyond the scope of discussion here based on the forum electrical safety rules. Not sure why this thread has been allowed to run assuming the rule applies equally to every thread starter.

The answer of course is not to use crappy foil shields which in any case are intended for high frequency signal shielding. Braid shielding is better for mains frequency and is tougher.

To ban this thread would be silly as no one is suggesting tampering with the mains supply. There are plenty of threads in DIY about work in DIY valve amplifiers which involve higher than main voltages and for obvious reasons those discussions are allowed.

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