1960s Earthing/ Bonding question

[AndyPRK]

Out of interest a question for those that are aware of late 1960's regulations, more out of curiosity than anything.

A building with a downstairs house and an upstairs flat.
They share the same water supply and pipework.
TT earth rod installed.

Separate fuseboxes

The water supply is bonded via the cooker circuit to ground floor CU

The upstairs flat has a VOELB (say 50v) near the building supply and earth rod

All good for the period so far I think.

An earth link has been installed (in period) between the 2 fusesboxes, hence the VOELB never operates! (as it's in effectively shorting the 2 earth terminals on the VOELB)

Why has this earth link been installed? Maybe to ensure the water pipes in the flat are at the same potential as the electric install? but I don't think it is required?

How should this HAVE been done in period?

The CU's now have 30ma RCD protection.
Is it ok to remove this earth link?

 

[EFLImpudence]

...

 

[EFLImpudence]

Is there just the one earth rod for the two properties?

 

[AndyPRK]

yes 1 rod

 

[EFLImpudence]

In that case, is the earth rod connected to both CUs separately or does the earth link achieve that?

 

[ericmark]

Good question, this is why the ELCB-v was discontinued, it was too easy for it to be by-passed. I know at around 14 I managed to connect the line to earth, and it ruptured the 13 amp fuse in the plug, but at 65 came to work on parent's house, and the only earth I could find was for the GPO party line.

I realised he had wall lights without an earth, ceiling lights would have been permitted pre-1966, but not wall lights.

Furthermore, I came to work on a log cabin, and testing the RCD it failed to trip, and I found an ELCB-v in a stone cottage from where the log cabin was fed, the tester I should have used would have looked like this I have never actually seen one, only pictures, and one wonders how anyone tested them, we should do a PIR every 10 years, and simply can't see how we could have done a PIR (now called EICR) without the tester?

But dad's house would have had a metal water pipe supply, so the ELCB-v would have never worked, and until the water pipe was changed to plastic there was no need for the ELCB-v their life was very short-lived, came in late 70's and gone by early 80's, think I only came across them twice, the other time was a caravan site, with static caravans.

 

[Adam_151]

The water supply should be bonded at the point of entry to the upstairs flat where the incomming service comes in. I suppose if there is only one earth rod, then they have probably decided its better to treat the whole thing as one equipotential zone, hence the bond between the two boards, and while they could have avoided shorting the ELCB by connecting it to the earth rather than fuseboard side. These things are always going to be affected by parallel paths and you'll find adding an immersion heater or gas boiler has a very similar effect. Its why they have been obselete for nearly 40 years.

The VO-ELCB needs be removed, while depending on how the supply to the fuseboards has been installed, while it might be that its not needed (but that relies on there not being any non-rcd ways, and the tails and internal wiring of the fuseboards being such that a fault to earth cannot occur) best solution is to replace with 100mA time Delay RCD, these used to be expensive, now there are many makes such as CP fusebox available at very reasonable cost, its a no brainer to just put one in, and be covered (and have some redundancy on failed RCDs in respect of fault protection)

 

[flameport]

How should this HAVE been done in period?

The described method was to have a VOELCB which connected to an earth electrode using a single insulated wire. Everything else was connected on the installation (frame) side of the VOELCB including any bonding.
This resulted in problems where the bonding itself was of lower resistance than the electrode, and warnings about them not working in such situations were included as far back as the 1930s and possibly earlier, along with requests to actually test the devices in situ to ensure they did actually operate.

The other option would have been to connect all bonding to the electrode side, and only have the protective conductors of the circuits on the frame side, but that has the problem of the installation being connected to the bonding via the solenoid coil, which would make it ineffective due to the coil resistance. Any failure of that coil would also result in the bonding being disconnected.

Summary - VOELCBs were junk even when in use, and their demise couldn't have come soon enough.
The fact they remained as an option into the 1980s, decades after current operated RCDs were available is a massive failure.

 

[AndyPRK]

In that case, is the earth rod connected to both CUs separately or does the earth link achieve that?

The CU's have their own earth supply.
The link isn't doing that.

Yes, the flat has an immersion heater. I have always thought the plumbing was bypassing the VOELB, but this link wire is doing a better job.

 

[AndyPRK]

Yes, the ground floor has a timedelayed RCD for belt and braces. The flat will get one installed to replace the VOLEB at some point.

In the mid 1970's some major building work was undertaken (ground floor) and a 500mA RCD was fitted for the ground floor.
What was there before hand I don't know. But if I were to guess, another VOELB.

That would have meant 2 VOELB with this link wire joining the 2 frame terminals. I guess this was slightly safer.
I assume under a fault condition, both VOELB's would trip ??!!
But you would need twice the voltage? 100v ?

It would have made more sense for there to be just 1 VOELB, but the seperate meters and main fuses would HAVE prevented this

 

[Taylortwocities]

Yes, the ground floor has a timedelayed RCD for belt and braces. The flat will get one installed to replace the VOLEB at some point.

In the mid 1970's some major building work was undertaken (ground floor) and a 500mA RCD was fitted for the ground floor.
What was there before hand I don't know. But if I were to guess, another VOELB.

That would have meant 2 VOELB with this link wire joining the 2 frame terminals. I guess this was slightly safer.
I assume under a fault condition, both VOELB's would trip ??!!
But you would need twice the voltage? 100v ?

It would have made more sense for there to be just 1 VOELB, but the seperate meters and main fuses would of prevented this

Its not worth thinking about. As @flameport has said, the VOELCBs never properly worked and any subsequent bonding work will bypass the VOELCB's detection coil. Junk them and provide RCD protection to both properties. And that does not mean a 500mA one.

 

[AndyPRK]

500ma one has gone.

 

[Jurassicspark]

Out of interest a question for those that are aware of late 1960's regulations, more out of curiosity than anything.

ELCB's were omitted from the 15th Edition in 1985.

It won't help someone touching the nicked wire on a lawnmower in the garden.

Last time I saw one was converted into a RCD.

 

[AndyPRK]

As previously said, the CUs have 30ma protection now.

Just curious why the bell this link has been installed that would have fooled the voleb
But now remember plumbing is also linking

 

[ericmark]

I did wonder when the ELCB-c replaced by the ELCB-v, Since they were both called ELCB I was not sure when we officially stopped using them. I seem to remember it was a bit like the unidirectional and bidirectional, and type AC or A RCD's today, we used for ages then they realised their use was flawed.

But by that time loads had been fitted.

The one I found in the woodland log cabin fed an RCD, so clearly who ever fitted the RCD never tested it, as it would not have ever worked.

The owner was not the type of person to have done DIY on his own electrics, so it would seem likely an electrician fitted it, not even the test button worked, I had worked out that I had no earth, and got some earth rods, as I was unaware of the old stone cottage it was fed from, but it was so clear there was basic no earth to the cabin, can't understand why the installer had not realised there was a fault.

However, in the 70's if I asked to read the regs book, or to use the mega, the foreman would quiz me as to why I wanted them, in 1991 the sixteenth edition came out, and for the first time we started taking exams on our knowledge of the regulations, and there was a massive change in attitude, until 1991 it was a case we do it this way because we have always done it this way, I went abroad in 1980 and returned around 1992 and all I would here electrician electricians say was, the 16th edition says this or that.

I think it was when the wiring regulations became BS 7671:1992 that people started to take notice of what they said.