BS7671:2018 Proposed Changes

[Ian1981]

It hasn't suddenly become dangerous overnight, the danger has been there, and been slowly increasing for many years.
The problem is broken PEN conductors, there was an article posted on here about it not so long ago.
A lot of our distribution system is somewhat antique with lots of new alterations and repairs with conversions to TNCS.

The requirement to install earth electrodes connected to the MET has been common in other countries for many years and its introduction here is a good thing in my opinion, but only if they get the regulations right with regards to Ra values.

Yeah I posted it after receiving an email from the electrical safety council.

 

[Ian1981]

But that all earthing and bonding must be up to standard. I'd read that as sticking an earth rod in aswell under these new rules.



I understand the dangers with PEN conductors and how having an earth rod would reduce the risk, but why not just apply this ruling to TNCS? The draft says "supplementing any earthing facility provided by the distributor" - so why are they pushing it on TNS as well? Is it just to make sure they tick the boxes, so that any TNS that are later converted to TNCS for whatever reason will be covered?

I love how the supply authorities issue becomes the installers problem!

 

[davesparks]

I understand the dangers with PEN conductors and how having an earth rod would reduce the risk, but why not just apply this ruling to TNCS? The draft says "supplementing any earthing facility provided by the distributor" - so why are they pushing it on TNS as well? Is it just to make sure they tick the boxes, so that any TNS that are later converted to TNCS for whatever reason will be covered?

I assume it is due to the widespread conversion of TNS services to TNCS.
I'm not sure that there will be many TNS services out there which are fully TNS these days.
Plus TNS isn't perfect and can suffer from a loss of its earth connection.

 

[static zap]

t ...AFDD's ....

If clever enough should be good , but if noise is external to
premises , could be back to "Nuisance value !"
(with less AM radios about , some are less aware of
consequences of gentle buzzing noises ! )

 

[Risteard]

Most of the rest of the world has required Earth electrodes on TN-C-S systems from year dot. It's about time it was required by BS7671.

 

[Ian1981]

Does actually any other European country use tncs?
Always thought it was a uk thing

 

[Rpa07]

Are there any statistics regarding the failing of PEN conductors and their occurances?
There surely are monitoring systems available to DNOs for these occurances leading to rapid responses.
I thought that TNCS was the future but if wrought with SO MUCH DANGER and the possible need for earth rod back up at every install, it strikes me as not that advanced!

 

[Andy78]

My initial thought is that if this is felt necessary as a requirement for safety due to the nature of the incoming supply, should this not be introduced into ESCQR and not have the onus for this safety measure put upon the end user ?

 

[davesparks]

Are there any statistics regarding the failing of PEN conductors and their occurances?
There surely are monitoring systems available to DNOs for these occurances leading to rapid responses.
I thought that TNCS was the future but if wrought with SO MUCH DANGER and the possible need for earth rod back up at every install, it strikes me as not that advanced!

Tncs is the future because it's cheaper to install, that's the main driving force behind its use.
Nobody is saying that there is SO MUCH DANGER, just that there is a danger and it should be mitigated.

 

[davesparks]

My initial thought is that if this is felt necessary as a requirement for safety due to the nature of the incoming supply, should this not be introduced into ESCQR and not have the onus for this safety measure put upon the end user ?

Increased csa of main bonding is a requirement for safety due to the nature of the incoming supply (PME) as is the use of rcds for fault protection (TT), nobody expects the DNOs to foot the bill for it so why should this be any different?

 

[Andy78]

Increased csa of main bonding is a requirement for safety due to the nature of the incoming supply (PME) as is the use of rcds for fault protection (TT), nobody expects the DNOs to foot the bill for it so why should this be any different?

Yeah good point.

I hope guidance is brought out as to what is expected of an installed electrode for these purposes though. Round these parts a 3/8" rod bashed halfway into the mud and rubble under the floor under the stairs seems to constitute a permanent TT arrangement when the sparky can't be bothered to call the DNO and wait a couple of weeks for a connection.

 

[Ian1981]

Increased csa of main bonding is a requirement for safety due to the nature of the incoming supply (PME) as is the use of rcds for fault protection (TT), nobody expects the DNOs to foot the bill for it so why should this be any different?

Then why not do away with that possible problem and go back to TN-S?
Cost is the reason pure and simple.
no risk of raising the earth to mains potential due to open pen conductor and no diverted neutral currents.
Earth can still fail of course.

 

[telectrix]

sod it. i'm going back to the 16th. RCDs only where sensibly required, CUs didn't spontaneously combust, no 5wws, shared neutrals save cable, no cat 5 run everywhere, sound in every room created by leaving doors open and turning the volume up. and only 4 channels of garbage on the telly instead of 200 . good old days.

 

[Pete999]

sod it. i'm going back to the 16th. RCDs only where sensibly required, CUs didn't spontaneously combust, no 5wws, shared neutrals save cable, no cat 5 run everywhere, sound in every room created by leaving doors open and turning the volume up. and only 4 channels of garbage on the telly instead of 200 . good old days.

BBC1 BBC2 ITV and C4 if you were lucky Apprenticeships, Plastic CUs and on and on and on. Glad I'm out to grass, or out to Red Vino, never did like grass, gives me Hay Fever, as well as a hangover. Tried that Mid Eartern stuff once Gaaat I think it was bit like a Privet hedge.

 

[Pat H]

Further to my post on the other thread can anyone find anything about AFDD's and where they will be required, other than they may be fitted!

How an Arc Fault Detection Devices (AFDD) can prevent electrical fire? - http://blog.schneider-electric.com/power-management-metering-monitoring-power-quality/2013/07/03/do-you-know-an-arc-fault-detection-device-afdd-can-prevent-from-an-electrical-fire/