UK Legal Details - Sockets - Where is the requirement for separate socket earths to be linked?

[wilmer000]

I have come across a double socket where the earth terminations aren't linked together - Is this illegal (and what regulation do i look at?) or is it allowed, and I just put the loop-earth in one termination and join the unearthed socket with a length of Earth conductor?

 

[wilmer000]

The maximum load from a 2G 13A socket is usually taken as 20A. Where does this figure come from? Written into legislation somewhere, manufacturer's instructions or just a convention?

That is in BS 1363-2, "16 temperature Rise" 16.1.2 for fixed sockets, using Table 10. "loading of sockets for temperature rise test". - 2 outlets are loaded with 1*14A+1*6A, total nom. load on supply cable 20A.

 

[Lucien Nunes]

What we might have to rely on is the inadequate instructions. They mention a single earth wire, which cannot reasonably be understood as a wire to one terminal and a link to the other. Nor would a person skilled and qualified in electrical installation work be expected to know that a link is needed. Whilst such a person would test the completed work, which would reveal the issue in many cases, an end-of-radial tested at whichever socket has the CPC connected would show nothing abnormal. Even in RFC or middle of a radial, a fortuitous connection between the two terminals via the screws and back-box could yield satisfactory test results without the connection being adequately reliable.

 

[netblindpaul]

What we might have to rely on is the inadequate instructions. They mention a single earth wire, which cannot reasonably be understood as a wire to one terminal and a link to the other. Nor would a person skilled and qualified in electrical installation work be expected to know that a link is needed. Whilst such a person would test the completed work, which would reveal the issue in many cases, an end-of-radial tested at whichever socket has the CPC connected would show nothing abnormal. Even in RFC or middle of a radial, a fortuitous connection between the two terminals via the screws and back-box could yield satisfactory test results without the connection being adequately reliable.

Bring back ductor testing?...

 

[wilmer000]

Hi everyone, I'd just like to say thanks to you all for helping me understand the implications of this. I'd be really interested to hear what Electrical Safety First or the BSI have to say about it if you get feedback from them. Some forums have a "thanks" button for their kudos system but I can't see one here, so thanks to all!

 

[netblindpaul]

@Pete999 have you not heard of Ductor testing?
High current low resistance testing.
Megger DLRO is a very common unit.
Mine is only 10A, but they are available up to 600A they stress the conductors to a higher level than the low current testing done by a typical MFT, or DMM.
They also offer a resolution much higher than those given by a typical MFT.
The way that EN 60204-1 is worded it is easily interpreted to require high current testing for all protective conductor networks.
A classic use for a Ductor was to test steel conduit when installed and utilised as the circuit cpc.

 

[DPG]

@Pete999 have you not heard of Ductor testing?
High current low resistance testing.
Megger DLRO is a very common unit.
Mine is only 10A, but they are available up to 600A they stress the conductors to a higher level than the low current testing done by a typical MFT, or DMM.
They also offer a resolution much higher than those given by a typical MFT.
The way that EN 60204-1 is worded it is easily interpreted to require high current testing for all protective conductor networks.
A classic use for a Ductor was to test steel conduit when installed and utilised as the circuit cpc.

Sounds like the high current earth bond test offered by some of the more expensive 'PAT' testers, including my fairly vintage Seaward one which does 25 amp low resistance testing.

Is ductor a trade name like Megger?

 

[netblindpaul]

Sounds like the high current earth bond test offered by some of the more expensive 'PAT' testers, including my fairly vintage Seaward one which does 25 amp low resistance testing.

Is ductor a trade name like Megger?

Very similar concept to the high current test used in PAT.
Ductor isn't a trade name AFAIK.
They are also known as I said above as high current low resistance testers, or micro/milli Ohmeters.
Megger DLRO10HD, DLRO200, Chauvin Arnoux CA6240/6255/6292 for example.
I have the DLRO10HD.

 

[DPG]

Very similar concept to the high current test used in PAT.
Ductor isn't a trade name AFAIK.
They are also known as I said above as high current low resistance testers, or micro/milli Ohmeters.
Megger DLRO10HD, DLRO200, Chauvin Arnoux CA6240/6255/6292 for example.
I have the DLRO10HD.

Cheers.

 

[Pete999]

@Pete999 have you not heard of Ductor testing?
High current low resistance testing.
Megger DLRO is a very common unit.
Mine is only 10A, but they are available up to 600A they stress the conductors to a higher level than the low current testing done by a typical MFT, or DMM.
They also offer a resolution much higher than those given by a typical MFT.
The way that EN 60204-1 is worded it is easily interpreted to require high current testing for all protective conductor networks.
A classic use for a Ductor was to test steel conduit when installed and utilised as the circuit cpc.

I have heard of Ductor testing, although I have never had the opportunity or experience of operating such a tester, was only asking out of interest.

 

[DPG]

Those testers look like they have an amazing level of accuracy. Reminds me of the short circuit location testers we used to use on circuit boards.

 

[pc1966]

Yes, fantastic to be able to resolve 10 microhoms!

I really want one now, but can't justify spending £2k-ish for my tool collection

 

[nicebutdim]

I have heard of Ductor testing, although I have never had the opportunity or experience of operating such a tester, was only asking out of interest.

I think confusion can arise from use of the "more information" emoticon as it looks very similar to "disagree"

 

[netblindpaul]

Those testers look like they have an amazing level of accuracy. Reminds me of the short circuit location testers we used to use on circuit boards.

They are a 4 wire bridge measurement type device, so they automatically "null" out the lead resistance and you can even use them with two 50m wander leads within limits.
For me it was well worth the cost.

 

[Lucien Nunes]

I have a vintage one (naturally). I think the actual trade mark is 'Ducter' with an 'e', which is registered to Megger having started out as an Evershed and Vignoles product around the same time as the Megger.

 

[netblindpaul]

I have a vintage one (naturally). I think the actual trade mark is 'Ducter' with an 'e', which is registered to Megger having started out as an Evershed and Vignoles product around the same time as the Megger.

I always thought that as it started as "Con_ductor_ Tester", it was ductor, rather than "Con_ductor Tester_".
Though I wouldn't want to argue or labour the point as E&V have been gone a LONG time now!
Most of the modern references are to Ductor rather than Ducter, which adds to the confusion.