Does anyone know what to say to UKPN who will be attending one of our properties for pitch leaking problems, the lady on the phone informed me that a BS951 clamp on a TN-S is not there concern and i should consider a TT or apply for PME?
I hate call handlers reading from a preset script who have little or no knowledge of what they are on about and doctor's receptionist triaging patients are top of the tree
Tricky. Can you prove they ever supplied an earth?
(I would have started by saying "what do your records show about earthing at this property?")
But actually if they are attending for pitch leaking, they might just sort it, so it might pay to just see what happens.
The 951 clamp is a good indication to me that there is good earthed metalwork on the DNO cable and they have supplied an earth at some point in the past
Even if TT or PME were to be used then the old TN-S cable would still need the sheath bonding. Which again should be done by the DNO - not using a BS951 clamp imo.
This is the argument I always use
I'd raise it with the engineer who comes out - perhaps while offering a tea! They might well do it on the spot if the head is suitable and tests OK.
Something I didn't realise, but was raised in one of the e5 webinars a while back - there was a period in the 70s (I think) when a BS 951 clamp was approved for DNO earthing, so it's not impossible that it's original.
The last time I had a DNO at a property for something and one was there, they replaced it with a spring loaded clamp, so that might be another option to ask the engineer.
The guy's on the ground are usually very good and at times critical of those handling the initial call, only ever had one who trotted out the TT spiel at a property that had been recently purchased for rental, there was no earth or rod on the installation and the CU had an upfront RCD and the DNO guy was adament that the installation was always TT even when it was pointed out to him that the sheath gave a Ze of 0.3Ω and he was probably confused by the houses a few streets away that were TT because they were mural wired, the fact that the service head was quite new and obviously replaced a metal service head that was connected to the sheath for the earth just seemed to go over his head
After the DNO guy left I rang the DNO again and requested that the job wasn't closed and should be elevated to an engineer a call a few hours later from an engineer after a little chat confirmed that the earth should be reinstated and a job was raised
Rather than highlight the BS951 clamp, ask for an earth to be instated. I think there is every possibility the BS951 clamp could have caused the pitch leak as it crushed the Lines together, just maybe? So that could be something to argue? I agree wiht the wait and see approach as the crews are much more practical and helpful than the office phone people. You could also talk to the supervisor if you really are not getting anywhere.
That is a new one on me although I have heard of overtightened 951's causing cables to overheat and cause fires
A conversation with a couple of DNO guy's a couple of years ago who had just replaced a service head and removed a number of dodgy 951 clamps and replaced them with a a couple of constant force spring clamps and a braided earth to a block went along the lines of you could just tighten the 951 clamps my reponse was thats what you do and how many times can you tighten a 951 earth clamp before you end up with a cable failure because it is overtightened, they both agreed that my caution was probably the best option and it kept them in work and occassional overtime
The last metal cut out that was leaking pitch I attended the DNO chap swapped the service head to a new one and also changed the BS951 clamp for a constant compression spring as the new earth connection.
On this one you could see where the old sweated earth had been before it was cut off by someone previously.
One before that they ended up replacing the lead cable back to the road and the cut out. Left it with a PME connection for me.
Most of their guys are spot on and very helpful round our way. He even left me a load of seals and tags!
Sy
What they replace the 951 clamp seems to vary between DNO's the two I regularly call one uses a constant force spring and the other one uses a jubilee type clamp
I think the suppliers earthing situation depends a lot on how hard the electrician on site digs their heels in with the evidence to hand it's an easy get out for the DNO to declare TT an once done the precedent is set, IMO a lot depends on how much experience the electrician has to argue the point
