Rewire.

[ebee]

Pipe lamps were common in the YEB area next to where I live but not in the Norweb area where I do live, I`m pretty sure YEB must have fitted them (they were not the "Tenby" sort either, they were in my opinion inferior to the tenby for contact and current carrying capacity onto the PILC and sometimes the connection was about 2.5 bare copper but you must take yours as 6.0 then later 10.0 too.

All that concluded to me that the actual electrical E was dependant upon the gas/water pipes in reality but not their theory, bonkers!
I did eventually get some to sweat on a 16.0 piece of earthwire to the PILC but they insisted (both YEB and Norweb) that the existing had to be compromised (or we had to pretend it was if anyone asked, otherwise policy dictated it should not be done because it was not deemed necessary t to be done!).

You could not make it up!

 

[securespark]

A succession of Norweb guys used to insist that the 2.5 or equivalent sweated onto the PILC was sufficient but without backing up their claim. One laughed when I mentioned the adiabatic and replied, "That's for you guys holding the regs, it doesn't cover us lot..." Which, to be fair is true.

This was in the days well before ESQCR 2002 and 7671 came out.

 

[plugwash]

If the values and calculators I've found online are correct then it looks like a 2.5 CPC would be good for an 80A BS88 but not a 100A BS88.

 

[ebee]

In the Norweb area 100A cutout was not unknown yet in YEB area I was aware at the same time YEB insisted as a sort of policy that supplies were often "Upgraged?" from a 100A to a 80A cutout to accomodate their own 16.0 tails from cutout to meter but as far as I am aware they could still insist on our meter tails from the meter to be 25.0mm not 16.0mm because they isisted that they could work to their "regs" but we had to work to what they required us to work to in effect, hm strange ???

 

[SUNRAY]

As for the

As I have said, solid green went out on 31 December 1977.

Wylex introduced the Standard range fusebox with a brown front and fuse cover and a brown wooden back and optional (I think phenolic) backplate in 1956.

With thanks to Flameport for the images.

View attachment 397674


In the late 1970s, they introduced an ivory version with an ivory painted wooden back and an ivory front and fuse cover.

View attachment 397675


A few years later, they moved on to an all plastic design in ivory, then a few years more to this.

View attachment 397676

There was a lot of variations in details across the ranges. I installed 3 in my house 1983, I had wood and plastic backs, all were down for on, in fact I don't recall seeing an up on before, other than RCD main switches

 

[SUNRAY]

The four houses I've lived in where I've got involved with the electric installation have all has copper clamps on the PILC.

My MET

 

[ebee]

Plenty of those connections to E at the time were not much better than a a piece of wet string yet when we supplied our bit it had to be a substantial Earthing conductor and main bonding conductors , it just did not make sense really,
It was just considered quite normal.

 

[EFLImpudence]

Plenty of those connections to E at the time were not much better than a a piece of wet string yet when we supplied our bit it had to be a substantial Earthing conductor and main bonding conductors , it just did not make sense really,

I don't think the two are are related.
The substantial conductors only became required when the DNOs failed to maintain their cables and lumbered everyone with TN-C-S.

It was just considered quite normal.

Back then it was normal.

 

[JohnW2]

The substantial conductors only became required when the DNOs failed to maintain their cables and lumbered everyone with TN-C-S.

The requirement has always felt a bit 'OTT' to me. Are there really a significant number of extraneous-c-ps which provide paths to earth of so low an impedance that the 'substantial bonding conductors' are really required with TN-C-S?

 

[EFLImpudence]

The requirement has always felt a bit 'OTT' to me. Are there really a significant number of extraneous-c-ps which provide paths to earth of so low an impedance that the 'substantial bonding conductors' are really required with TN-C-S?

Is the thinking not that you might be connected to a neighbours installation which does not have a lost neutral?

Like your bonding compared to your TT.

 

[JohnW2]

Is the thinking not that you might be connected to a neighbours installation which does not have a lost neutral? ... Like your bonding compared to your TT.

Good point. As you imply, given my situation I should really have thought of that one!

Mind you, I wonder how common 'my situation' (at least, what I assume to be the situation) actually is?

 

[ebee]

He is right about that one John, myself I have come across a few installations where the all the apparently good readings have only come about because main bonding is effectively giving a "good Ze" which disappears or very markedly increasing the ohms value because any previous tests have been carried it failing to disconnecting the bonding.
Disconnecting bonding to do a proper Ze test is very important if its neighbouring bonding is pretty much all that is holding your earth down, it could surprise some how often it is omitted because of the perception that it is a pain in the neck and unnecessary, yes it can sometimes be a bit of a pain and sometimes a real pain but you need to be sure, you really do.

Perhaps our friend has his nom de plume on this forum because he realised this very fact a long time ago?

 

[JohnW2]

He is right about that one John, myself I have come across a few installations where the all the apparently good readings have only come about because main bonding is effectively giving a "good Ze" which disappears or very markedly increasing the ohms value because any previous tests have been carried it failing to disconnecting the bonding.

As you must know, that is a situation with my house, but in my case it is almost a 'positive', rather than 'negative', surprise one gets if one measures Ze without disconnecting with bonding - since my installation is TT, such that I expect a 'very high' Ze (by TN standards)

With all bonding disconnected (i.e. leaving m,e with just my TT electrodes) my Ze obviously varies ('with the weather') but is generally in the range 50Ω - 70Ω. With the water supply pipe bonded, the Ze is consistently about 0.25Ω. That means that, since its intended to be a TT installation, I do not, and cannot, rely on OPD-mediated ADS (hence theoretically relying on RCDs for fault protection), the reality is that, with bonding connected, every single one of my final circuits has a low enough Zs for OPD-mediated ADS!

My immediate neighbour has a TN-C-S installation and we currently both have metal water supply pipes (bonded in both properties) which I presume are in electrical continuity with one another.

Disconnecting bonding to do a proper Ze test is very important if its neighbouring bonding is pretty much all that is holding your earth down, it could surprise some how often it is omitted because of the perception that it is a pain in the neck and unnecessary, yes it can sometimes be a bit of a pain and sometimes a real pain but you need to be sure, you really do.

It's difficult to argue with that but, to be fair, the standard EICR form asks for Ze to be determined "by enquiry or measurement" and I suspect that a substantial proportion of inspectors will be claiming that they have determined it (for a TN earth) "by enquiry" (which, in practice, probably means assuming 0.35Ω for TN-C-S or 0.8Ω for TN-S)!

There is at least one of our contributors who is so prone to consider the 'incredibly improbable' who might mention the possibility of an EICR inspector dying as a result of disconnecting bonding ("to do a proper Ze test") at the very moment that there was a PEN fault on a TN-C-S supply!

It's probably also worth noting that there is at least one reason for determining Ze with bonding connected (as well as with it disconnected), particularly in a situation like mine, since, if one doesn't, one might theoretically miss a situation in which a CPC was adiabatically inadequate 'in normal use' (i.e. with bonding connected)

Kind Regards, John

 

[ebee]

As you must know, that is a situation with my house, but in my case it is almost a 'positive', rather than 'negative', surprise one gets if one measures Ze without disconnecting with bonding - since my installation is TT, such that I expect a 'very high' Ze (by TN standards)

With all bonding disconnected (i.e. leaving m,e with just my TT electrodes) my Ze obviously varies ('with the weather') but is generally in the range 50Ω - 70Ω. With the water supply pipe bonded, the Ze is consistently about 0.25Ω. That means that, since its intended to be a TT installation, I do not, and cannot, rely on OPD-mediated ADS (hence theoretically relying on RCDs for fault protection), the reality is that, with bonding connected, every single one of my final circuits has a low enough Zs for OPD-mediated ADS!

My immediate neighbour has a TN-C-S installation and we currently both have metal water supply pipes (bonded in both properties) which I presume are in electrical continuity with one another.


It's difficult to argue with that but, to be fair, the standard EICR form asks for Ze to be determined "by enquiry or measurement" and I suspect that a substantial proportion of inspectors will be claiming that they have determined it (for a TN earth) "by enquiry" (which, in practice, probably means assuming 0.35Ω for TN-C-S or 0.8Ω for TN-S)!

There is at least one of our contributors who is so prone to consider the 'incredibly improbable' who might mention the possibility of an EICR inspector dying as a result of disconnecting bonding ("to do a proper Ze test") at the very moment that there was a PEN fault on a TN-C-S supply!

It's probably also worth noting that there is at least one reason for determining Ze with bonding connected (as well as with it disconnected), particularly in a situation like mine, since, if one doesn't, one might theoretically miss a situation in which a CPC was adiabatically inadequate 'in normal use' (i.e. with bonding connected)

Kind Regards, John

John I do not disagree with any of that.
All to the good if you have a TT system and when connected to boding it effectively will have the benefits of becoming TN=like.
The only problem is that if bonding from say one system (yours) becomes disconnected from nearby bonding even though you keep your own there could become a problem if you are reliant on TN to bring about ADS. You could be startled by your own mortality.
If I had a TT system I would have an RCD to ensure disconnection and consider any bond links etc that bring Ze down to be a helpful thing in reality but not place reliance on them.
Subsequently any TN system is reliant on the incoming E but having an RCD as back up a good thing too.
If I had a TT system I would not rely on only one RCD I would try have another one to cut down the odds of a single point of failure too.
A bit OTT I know but I would rather reduce the possible 7% failure rate of a device that might actually be 95% effective excrement is thrown at a fan, gives me a slight hope of another little chance of not departing from this planet quite yet!

Slightly delusional ? Probably.

I used to smoke, went thru 60 to 80 a day for a number of years, not a good idea! I did stop over 20 years ago now, I probably would not be here otherwise.

 

[JohnW2]

John I do not disagree with any of that. All to the good if you have a TT system and when connected to boding it effectively will have the benefits of becoming TN=like.

Exactly. So long as the status quo remains unchanged, I thing of it as "TT+"

The only problem is that if bonding from say one system (yours) becomes disconnected from nearby bonding even though you keep your own there could become a problem if you are reliant on TN to bring about ADS. You could be startled by your own mortality.

Indeed. The greatest 'risk' is not that something would go wrong with the bonding within either of the houses but, rather, that the (presumed)) metal water supply pipe which is currently (presumably) joining our electrical installations (via bonding) could e changed to plastic 'one dark night'. That's why I wrote ..

...... That means that, since its intended to be a TT installation, I do not, and cannot, rely on OPD-mediated ADS (hence theoretically relying on RCDs for fault protection), the reality is that, with bonding connected, every single one of my final circuits has a low enough Zs for OPD-mediated ADS!

If I had a TT system I would have an RCD to ensure disconnection and consider any bond links etc that bring Ze down to be a helpful thing in reality but not place reliance on them.

As above, that's exactly my position and thinking.

If I had a TT system I would not rely on only one RCD I would try have another one to cut down the odds of a single point of failure too.

I have that sort-of 'covered', at least in terms of clearing faults before anyone gets a shock, since there are up-front 100 mA TD RCDs upstream of the RCDs (RCCBs and RCBOs) in CUs.

A bit OTT I know but I would rather reduce the possible 7% failure rate of a device that might actually be 95% effective excrement is thrown at a fan, gives me a slight hope of another little chance of not departing from this planet quite yet! Slightly delusional ? Probably.

I'll never knock anyone for being ultra-cautious, whether in terms of wanting redundancy of protective devices or anything else, even when I personally regard it as a bit 'OTT' (but even I would be very nervous stepping onto an aircraft if I wasn't aware of all the built-in redundancy!)

As for this "7% failure rate", people have been quoting that figure for very many years (probably 20+ years, maybe a lot more), hence based on some very old, maybe very 'early' (in terms of RCDs), data. I also seem to recall that the 'failure' in question related to 'testing', so many of that "7%" may have been only fractionally 'out-of-spec', which could be of little consequence given that the 'spec' itself is essentially arbitrary ... not to mention the fact that being 'early' the data may well have related to generations of RCDs less reliable than current ones. There surely must be a lot more, more recent data relating to recent devices?

However, as always remind folk, it's all very well being concerned about the reliability of RCDs for providing fault protection, but the alternative is to rely on MCBs or the over-current functionality of RCBOs - and since there is no practical way of routinely testing them, we really have no idea about their in-service reliability - maybe their 'failure rate' is 70%?

Kind Regards, John