Old wife's tail, myths, and other stories we were told as an apprentice, before the days when BS 7671 started.

[ericmark]

BS 7671:1992 started the exam and resulted in every electrician at some point having a copy to see for himself what the rules are. But before that, asking to see the regulations, was met with why do you want to see them boy, and we were told by the foreman what they said, he did not want our dirty hands on the book.

We if lucky would see one of the guides, at that time mainly complied by the Union, not the IEE later the IET as today, so around the 60's we started fitting ELCB-v and by mid 80's we were told they were banned, we started in 70's to go mad on earthing, even metal window frames, then that stopped, and when I went into an old bridge the switch to energise the motor still had open contacts, opened 1897 so clearly huge change since the third edition.

But were they really allowed even back then? I seem to remember seeing in one of the guides the distance a socket could be to a sink, but was that ever a regulation? I know last house socket was about 9 inches from sink, and the waste disposal unit plugged into it, socket supplied by a switch side of draining board.

We are all told 1966 the earth rules changed, and thanks to our @flameport I have now seen what was written, this was a surprise, as it seems wall lights had needed earths well before that, but they did not fit them to parents house built 1954, but likely the electrician like me in my early years had never seen a copy of the regulations. It was hard enough getting his head around the new ring final circuits.

So what old wives tales were you told as an apprentice?

 

[Diver Fred]

They didn't fit earths to light circuits in 1979 (I know 'cause that is when my property was rewired!). Caused me much grief sorting that out when I had an EICR a couple of years ago. Luckily all the points for the lighting was in conduit, just had to get flooring up.

 

[Jurassicspark]

This one I always hate to hear is "It's not the volts that kill/hurt you, it's the Amps."

That's like saying "It's not the height from which you fall that hurts you, it's your speed just before you hit the ground

 

[Jurassicspark]

They didn't fit earths to light circuits in 1979 (I know 'cause that is when my property was rewired!).

Most did. The person whoever wired it was probably either unaware or was just wanting to get rid of the old cable.

 

[JohnW2]

This one I always hate to hear is "It's not the volts that kill/hurt you, it's the Amps." .... That's like saying "It's not the height from which you fall that hurts you, it's your speed just before you hit the ground

That reminds me of a story about a local in the West Country who, at the top of a road which had a very steep 'fall' was asked whether it was safe to drive down the road. He answered that it was perfectly safe actually driving down the hill, because it was only at the bottom that car occupants regularly met their deaths

However, the electrical 'proverb' is far from totally daft, since it reminds us that a very high voltage can be pretty 'harmless'if it has a sufficiently high internal resistance (such as to seriously limit the current that can flow through a victim). That's not only true of 'electrostatics', but also things like the EHT supplies of CRTs gthat were, in the day, derived from line output transformers or the 'traditional' (non-electronic) car ignition systems. In those cases,voltages of tens of kV were not able to result in currents more than 'microamps' through a victim - hence very rarely killed anyone!

Kind Regards, John

 

[Murdochcat]

They didn't fit earths to light circuits in 1979 (I know 'cause that is when my property was rewired!). Caused me much grief sorting that out when I had an EICR a couple of years ago. Luckily all the points for the lighting was in conduit, just had to get flooring up.

If its steel conduit, that is the earth / cpc

 

[Diver Fred]

If its steel conduit, that is the earth / cpc

Unfortunately, the conduit wasn't continuous - it just went down the walls.

 

[Harry Bloomfield]

This one I always hate to hear is "It's not the volts that kill/hurt you, it's the Amps."

That's like saying "It's not the height from which you fall that hurts you, it's your speed just before you hit the ground

Which is perfectly true. Back in the day, I would be not too bothered by a colour TV's 28Kv, because the current delivered was relatively tiny.

 

[Harry Bloomfield]

If its steel conduit, that is the earth / cpc

Only if it is threaded conduit - there used to be a lot of grip conduit about, in domestic environments.

 

[Adam_151]

I have now seen what was written, this was a surprise, as it seems wall lights had needed earths well before that

It was any class 1 fitting that could be reached while standing on the ground wasn't it? I imagine a big metal chandelier on a standard 8 foot domestic ceiling would have required a CPC even back then.... its just that pendant sets were all that generally got installed so it was never an issue except when wall lights or lamp sockets were fitted.

I looked at an installation probably from around '64 a few months back. No CPC to the lighting circuits, but wall lights in the lounge did have earth continuity, there was a socket quite close to below each one and they had taken a bare 3/0336 ECC back up the capping to earth the wall lights off the ring cirucit. It looked to have been a pretty good instalaltion for its time before the DIY bodgers came in (someone had used a 15A MEM rewireable switchfuse as the garage Sub-board, and had reversed the polairty comming into it so the 3036 was in the neutral)

 

[Murdochcat]

Another myth still peddled is that the NICEIC write the regs

 

[JohnW2]

Which is perfectly true. Back in the day, I would be not too bothered by a colour TV's 28Kv, because the current delivered was relatively tiny.

Quite so - as I wrote ...

.... things like the EHT supplies of CRTs that were, in the day, derived from line output transformers or the 'traditional' (non-electronic) car ignition systems. In those cases,voltages of tens of kV were not able to result in currents more than 'microamps' through a victim - hence very rarely killed anyone!

 

[ericmark]

Some times when hunting for some thing in BS 7671 I come across something which I did not think was a regulation, I know I work out volt drop using the loop impedance, I did not realise this is in the regulations under inspection and testing, what seems strange is one needs to check the volt drop, but there is no place in the standard form to record the volt drop.

 

[SUNRAY]

Only if it is threaded conduit - there used to be a lot of grip conduit about, in domestic environments.

And that was used as the earth too. I grew up in a 1951 built council house with that arrangement and still in use today and still passes EICR.

 

[Harry Bloomfield]

And that was used as the earth too. I grew up in a 1951 built council house with that arrangement and still in use today and still passes EICR.

Really? I was heard it just would not do, because of the electrical unreliability, of the joints. I half remember that it became customary, for the threaded conduit, to include a separate earth wire.