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Bonding

Guy Chapman
I have an extension going on to my house and it has engineered joists. I am going to run cables in steel tray, for tidiness, and I am assuming this would be considered an ECP and should be bonded (that makes obvious sense to me). It will carry ring and lighting circuits. I cannot imagine that more than 10mm2 would be required for this, but every time I read new guidance they seem to have upped the ante. What do people think? And do you use link jumpers between sections of tray, or are the bolts sufficient? I've not seen anything to suggest that copper jumpers are needed, and we don't use them in datacenters (the day job), but that's just CAT7 and fibre.


Also because Reasons there are no spare ways on the earth block on the board. Do I have to source an earth block of more than 8 ways or is it legit to join two blocks together with 16mm2? I don't want to look like a pillock and have the sparks refuse to energise the circuits when done.


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    You know what, I think you are right. I think I need a copy of Guidance Note 8 to be certain but as it doesn't come in from outside the building, and the cables are all insulated, then it does not seem to meet the definition of extraneous-conductive or exposed conductive. I confused the two, I reckon. But UKPN makes a good point too. You can make a case for earthing it (as there are plausible fault conditions due to mechanical damage that could lead to the part becoming live). There's no data, I run ELV physically separated, so no real EMC issue so the real question is, would earthing the tray introduce a potential hazard. I guess that would be an ecumenical matter.


    I found this rather useful discussion: https://www.tradeskills4u.co.uk/posts/metallic-cable-tray


    I think the answer is: it doesn't need to be bonded, it probably doesn't need to be earthed, there might be additional risk if it was earthed, so maybe don't. This turns out to have been a much more interesting question than I thought, and I thank everyone for their thoughtful and helpful input.
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    You know what, I think you are right. I think I need a copy of Guidance Note 8 to be certain but as it doesn't come in from outside the building, and the cables are all insulated, then it does not seem to meet the definition of extraneous-conductive or exposed conductive. I confused the two, I reckon. But UKPN makes a good point too. You can make a case for earthing it (as there are plausible fault conditions due to mechanical damage that could lead to the part becoming live). There's no data, I run ELV physically separated, so no real EMC issue so the real question is, would earthing the tray introduce a potential hazard. I guess that would be an ecumenical matter.


    I found this rather useful discussion: https://www.tradeskills4u.co.uk/posts/metallic-cable-tray


    I think the answer is: it doesn't need to be bonded, it probably doesn't need to be earthed, there might be additional risk if it was earthed, so maybe don't. This turns out to have been a much more interesting question than I thought, and I thank everyone for their thoughtful and helpful input.
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