How do they know about the Tenby clip ?
High earth reading
- Thread starter Inderpal
- Start date
How do they know about the Tenby clip ?
To clarify, the dno don't like the fact that a regular gas/water bonding clamp has been used, and presumably they want to see the 'proper' earth clamp that is supposed to be used.
If you changed the clamp for something more 'proper', would they come out and sort it out?
(Sounds like you sent them a photo - never, never do that...)
If you changed the clamp for something more 'proper', would they come out and sort it out?
(Sounds like you sent them a photo - never, never do that...)
We can but guess what the situation is. However, as I wrote, maybe they regard the fact that it has such a clamp (which, as you say, they presumably can only have ascertained from a photo) to indicate that they did not provide a TN-S earth (i.e. regard the installation as TT) but that 'someone else' has tried to- in which case they would, of course,have no obligation in relation to, or responsibility, for maintaining the earth.
Usually the DNO should have records of which area has which earthing arrangement.
If the DNO has provided an earth. They must maintain it.
I'm certain a BS951 earthing clamp is deemed unacceptable for providing the earth from a supply cable - even though 'everyone' does it.
I imagine it's one of those situations where the company won't touch it if it doesn't meet their criteria, even if electrically it makes no difference.
They should,but often don't seem to be sure when asked. However, as I wrote, they may be assuming that since the 'apparent TN-S' uses a clamp which they don't use, then it is is not an earth which they provided, hence not an earth which they have to maintain.
In other words, if they do not believe that it is a TN earth which they provided, they will presumably believe ()and theior records should show) that it is meant to be TT.
... and the converse. See above in relation to the situation in which they believe that they have NOT provided an earth.
Quite so - 'everyone' other than themselves.
... and I've just written, maybe it is an indicator to them that they didn't provide the earth, and therefore do not have to maintain it.
Whats the bet on it being a TT installation then?
It is very very unlikely that one will acheive a stable Ra anywhere near good enough to allow enough fault current to flow, in order to trip any MCB.
Bear in mind that the only decent way to acheive discrimination with RCD's is to use S types. RCBO's are a good way to go too.
By looking at the install I doubt it was a TT.
The BS951 clamp is much newer than the supply cable. It will have been fitted by an electrician, who has replaced the 'original clamp'.
Who will have fitted the 'original' clamp, decades and decades ago?
Who will have fitted the 'original' clamp, decades and decades ago?
Right.
Regarding the connection, it should be either a sweated connection or constant force spring.
A lot of people say it's a C2 and a call to the DNO, so I'm sure they might/can do something? No one wants to see a situation of a shorted incomer.
A few things- that cutout is ancient and has a rewireable fuse so could do with being replaced.
The Tenby clip looks to have been installed by someone and has been put on the armours of the cable hence the high reading.
The only real way to determine weather the earth on the supply is usable is to replace the whole cutout and strip back the armours to bare lead.
The supply would have to be made dead also due to it being cast iron.
A lot of work for the DNO so that may have swayed their decision to leave it as is.
The earth on the cable may have never been connected at the Tee joint in the first place so that’s why the armours aren’t stripped back.
I don’t know UKPN’s rules on this but the DNO I work for this would be the case and we’d have to try and resolve the issue
The Tenby clip looks to have been installed by someone and has been put on the armours of the cable hence the high reading.
The only real way to determine weather the earth on the supply is usable is to replace the whole cutout and strip back the armours to bare lead.
The supply would have to be made dead also due to it being cast iron.
A lot of work for the DNO so that may have swayed their decision to leave it as is.
The earth on the cable may have never been connected at the Tee joint in the first place so that’s why the armours aren’t stripped back.
I don’t know UKPN’s rules on this but the DNO I work for this would be the case and we’d have to try and resolve the issue
A lot of people are wrong.
Clamp type connections were entirely permitted on cables in BS951 a few decades ago, until they were removed and then suddenly they became the most dangerous item ever.
However the item in the photo was certainly added very recently.
In any event, C2 and other similar codes described in BS7671 are not applicable to DNO equipment.
and as it's looped, 50/50 that they have attached it to the wrong one, i.e. the cable that goes next door instead of the incoming supply.
Indeed - so, given the absence of any up-front S-typoe RCD, whoever installed the CU (and maybe also even the clip/clamp on the incoming cable) presumably was considering it to be TN-S? However .....
... the 'bet' presumably needs to be on what sort of installation the DNO regard it as being, doesn't it?
Does that not imply that the DNO didn't do it (and therefore may not have "provided an earth")?
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If that's PILC then it won't be armour, but a lead sheath.
I have seen PILC where the DNO has put Tenby clamps on, albeit, temporarily.
I have seen PILC where the DNO has put Tenby clamps on, albeit, temporarily.
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