Wartime Civilian Receiver - Mains set - Grounding?

[Martin G7MRV]

I have just replaced the mains cable to our museums wartime civilian receiver. The original cloth covered rubber two core was not in a good state, in many places being distinctly hardened and in fact the insulation had crumbled within the plug.

I've replaced this with "vintage style" modern cloth covered 3 core flex. A little expensive at £3/m but certainly looks good!

This of course means I have a mains earth connection available. Should I bond this to the chassis?

I can't immediately see any reason not to do so, other than perhaps the risk of introducing noise

[Techman]

Strictly speaking, you can't legally do this. Fitting an earth where there wasn't one originally changes its 'class' and technically it would have to go through new type approval, which it wouldn't have a hope of meeting these days. It's important to get this sort of thing right if it's in a public building such as a museum. There's been loads written on this subject in the past.

[paulsherwin]

Agreed, it's problematic doing this on a commercial basis, and there could be consequential liability issues. This is one of those cases where modifying an electrical item to actually make it safer causes problems with the type approval regs.

In these circumstances I think I would actually use 2 core cable, even though it's less safe. It counts as a repair rather than a modification. Presumably it's only ever going to be used on RCD protected circuits.

[Station X]

If you do go ahead and earth the chassis there is a risk of insulation breakdown between the mains transformer primary winding and chassis/earth. There'll be 230VAC difference between these points with a three core mains lead, 0VAC with a two core mains lead.

[Martin G7MRV]

All duly noted,

Thanks