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V.O.E.L.C.B.
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3131 Posts
Question
It dawned on me fully today while working in an old holiday chalet circa 1940s.

The man in the next chalet was trying to use his old Black and Decker 1970s car boot sourced electric drill outside on the grass. He was making a wooden clothes hanger with wood and pegs. A jolly good job too.

I had had a quick look inside his chalet as he needs some new sockets. The  fuse box is an old cream coloured Wylex 6 way unit with fuse wire carriers. There is an old Crabtree V.O.E.L.C.B. installed before the fuse box.

As he worked in the garden drilling wood, it dawned on me that he had zero shock protection as he would if he had a R.C.C.B. installed.

It's strange how a picture speaks a thousand words.

Z.

 
57 Replies
Sparkingchip
4245 Posts
What is the tripping current of a Voltage Operated Earth Leakage Circuit Breaker?
broadgage
725 Posts
Sparkingchip:
What is the tripping current of a Voltage Operated Earth Leakage Circuit Breaker?

They do not have a tripping current.
They trip when the VOLTAGE between true earth (earth rod) and the earth wires of the installation reaches a certain figure, often 50 volts.
So if a defective class one appliance raises the voltage of the green wires in the house to more than 50 volts, it should trip.
If working correctly they give reasonable protection to persons within a home, against any defect in the wiring or appliances of that home.
In the case of equipment used outdoors they give very limited protection.
If the electric drill had a short circuit between phase and earth, that should raise the system earth voltage to more than 50 volts, and promptly trip the supply.
If however the flex of the appliance was damaged, and the user touched the phase wire, they would get a serious and perhaps fatal shock. There is no way that a VOELCB will "know" the difference between an amp passing through a human to earth, and another amp of load current.
The other risk is if pre-existing earth leakage had raised the system earth voltage to 49 volts, A class one appliance used outdoors would give the user a 49 volt shock. Much less dangerous than line voltage, but still twice the limit of SELV.

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3131 Posts
broadgage:
Sparkingchip:
What is the tripping current of a Voltage Operated Earth Leakage Circuit Breaker?

They do not have a tripping current.
They trip when the VOLTAGE between true earth (earth rod) and the earth wires of the installation reaches a certain figure, often 50 volts.
So if a defective class one appliance raises the voltage of the green wires in the house to more than 50 volts, it should trip.
If working correctly they give reasonable protection to persons within a home, against any defect in the wiring or appliances of that home.
In the case of equipment used outdoors they give very limited protection.
If the electric drill had a short circuit between phase and earth, that should raise the system earth voltage to more than 50 volts, and promptly trip the supply.
If however the flex of the appliance was damaged, and the user touched the phase wire, they would get a serious and perhaps fatal shock. There is no way that a VOELCB will "know" the difference between an amp passing through a human to earth, and another amp of load current.
The other risk is if pre-existing earth leakage had raised the system earth voltage to 49 volts, A class one appliance used outdoors would give the user a 49 volt shock. Much less dangerous than line voltage, but still twice the limit of SELV.

I am substantially in agreement with broadgage who is much more knowledgeable than me in most cases. I have read from manufacturers' literature that the V.O.E.L.C.B.s operated at well below the claimed 50 Volts max. to Earth. Typically 30 to 40 Volts is quoted. But of course they do not comply with the wiring regulations any more.

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3131 Posts
Zoomup:
broadgage:
Sparkingchip:
What is the tripping current of a Voltage Operated Earth Leakage Circuit Breaker?

They do not have a tripping current.
They trip when the VOLTAGE between true earth (earth rod) and the earth wires of the installation reaches a certain figure, often 50 volts.
So if a defective class one appliance raises the voltage of the green wires in the house to more than 50 volts, it should trip.
If working correctly they give reasonable protection to persons within a home, against any defect in the wiring or appliances of that home.
In the case of equipment used outdoors they give very limited protection.
If the electric drill had a short circuit between phase and earth, that should raise the system earth voltage to more than 50 volts, and promptly trip the supply.
If however the flex of the appliance was damaged, and the user touched the phase wire, they would get a serious and perhaps fatal shock. There is no way that a VOELCB will "know" the difference between an amp passing through a human to earth, and another amp of load current.
The other risk is if pre-existing earth leakage had raised the system earth voltage to 49 volts, A class one appliance used outdoors would give the user a 49 volt shock. Much less dangerous than line voltage, but still twice the limit of SELV.

Oh ek. Words gone funny. I am substantially in agreement with broadgage who is much more knowledgeable than me in most cases. I have read from manufacturers' literature that the V.O.E.L.C.B.s operated at well below the claimed 50 Volts max. to Earth. Typically 30 to 40 Volts is quoted. But of course they do not comply with the wiring regulations any more.
 

V.O.E.L.C.B.s are mentioned in my 1976 14th edition but are not in my 1987 15th edition that I can find. According to John Whitfield's 17th Edition Electrician's Guide, the Voltage Operated Earth Leakage Circuit Breakers were deleted from the 15th edition in 1985.

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3131 Posts
Sparkingchip:
What is the tripping current of a Voltage Operated Earth Leakage Circuit Breaker?

They work like a Volt meter. If they detect a certain Voltage between earthed metalwork within an installation, and true Earth, they trip off and open their supply contacts to the load.

The applicable B.S. for V.O.E.L.C.B.s at the time was B.S. 842. It required them to operate at 24 Volts to earth with a 200 Ohm earth electrode, and at 40 Volts with a 500 Ohm earth electrode. Crabtree claimed that theirs were instantaneous in operation. I still find perfectly operational ones today, except that the earth rod may have deteriorated or earthing lead has been pruned through, as it may only have been a 2.5mm2 green insulated solid conductor. The great thing about the test button was that it confirmed not only operation of the unit, but also the effectiveness and condition of the earth rod and earthing lead (earthing conductor). They were very well made and were solid and clunky.

https://www.bing.com/videos/search?q=John+Ward+voltage+operated+earth+leakage&docid=608032099226879187&mid=D18E886DA26FA44990EBD18E886DA26FA44990EB&view=detail&FORM=VIRE

Z.

Sparkingchip
4245 Posts
VOELCB -Voltage Operated Earth Leakage Circuit Breaker.

They protect against leakage, but not efficiently. The installation was designed to get the same outcome with a VOELCB as with an RCD, both being available in the 1940’s, however the earthing arrangement could be tweaked to improve the performance of the VOELCB by doubling up on electrodes.


 
Sparkingchip
4245 Posts
Sparkingchip
4245 Posts
The basic requirements were the same to limit:
  • Voltage
  • Current 
  • Time
Current cannot be limited, but the minimum threshold for the protective device can be set.

The reality is that a RCD is more efficient and reliable than a VOELCB.

But there are still millions of VOELCB still in people’s homes in the UK despite having been obsolete for over forty years.
Sparkingchip
4245 Posts
Sparkingchip
4245 Posts
The electricians who installed the VOELCBs seventy years ago put far more consideration into installing earth rods than today’s electricians do, as the earthing was far more critical back then.

It is time to replace that old VOELCB with a far more reliable RCD that is less dependent on sound earthing, particularly out in the areas where homes are on sand and gravel, which includes where I live on the second alluvial plain of the River Severn. 
Normcall
60 Posts
I think you will find they have an inherent tripping current of 500mA
Sparkingchip
4245 Posts
I think 500 mA is realistic as Normcall‍  says, assuming 30 mA would be very foolhardy.

Time was a bit of an unknown, there isn’t any way to determine how long it took them to clunk off.

Testing was just applying voltage  to the earthing system with a transformer to see what happened, with the anticipation of a clunk.
Sparkingchip
4245 Posts
Zoomup:

The man in the next chalet was trying to use his old Black and Decker 1970s car boot sourced electric drill outside on the grass. He was making a wooden clothes hanger with wood and pegs. A jolly good job too.



 


A forty year old Black and Decker drill with a metal case, a Class I hand held appliance unlike the modern all insulated drills with plastic cases, being used outdoors?

That probably comes under the heading of foolhardy as well.

 

Chris Pearson
2686 Posts
Sparkingchip:
Zoomup:
The man in the next chalet was trying to use his old Black and Decker 1970s car boot sourced electric drill outside on the grass. He was making a wooden clothes hanger with wood and pegs. A jolly good job too.


A forty year old Black and Decker drill with a metal case, a Class I hand held appliance unlike the modern all insulated drills with plastic cases, being used outdoors?

That probably comes under the heading of foolhardy as well.

Are you sure that it is Class I? I have a Wolf drill which was old when I bought it 40 years ago and it is Class II even though the gearbox forwards is metal.

mapj1
3753 Posts
If it much more than 50 years old that marks about half time in the development of the pistol trigger hand drill -
history of electric drills, 1916 to date

beware the adverts

Time and the evolution of kit and manufacturing standards is a funny thing. Looking at that leaflet from 1940, 80 years ago, 1980 would be a mid point, and yet 1980 seems almost 'modern times' while as  I recall in 1980, stuff from  1940 felt like another much older era, but the interval is the same . Equally the youngsters tease me for stuff I recall as being 'so last century'.
Mike.

 
Sparkingchip
4245 Posts
I’m old enough to remember that the new fangled drills with the plastic bodies would never last as the metal bodied drills we had.

It’s not just about the electrical safety of the drill itself, if you drill through a live cable it’s far better to do so with a drill that has a plastic body.
Chris Pearson
2686 Posts
mapj1:
Equally the youngsters tease me for stuff I recall as being 'so last century'.

I still think of the last century as being the 19th Century. 😁

AJJewsbury
2698 Posts
it dawned on me that he had zero shock protection
Why?

If the drill is class I and correctly earthed and presuming the VoELCB is working, then ADS should occur as normal (and wuth less dependence on a good Zs too).

If the drill is Class II (which I rather suspect) then he has shock protection by double or reinforced insulation, the ELCB makes no difference.

It's lacking additional protection perhaps, but that's another matter.

  - Andy.
AdrianWint
53 Posts
So, using such a device but connected between a 'PME neutral/earth' & "true earth" would give a mechanism that would disconnect if they moved more than about 50V apart.

The VOELCB having the distinct advantage that it already has a set of high current contacts! 

Maybe they arent so useless after all!
 
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3131 Posts
AJJewsbury:
it dawned on me that he had zero shock protection
Why?

If the drill is class I and correctly earthed and presuming the VoELCB is working, then ADS should occur as normal (and wuth less dependence on a good Zs too).

If the drill is Class II (which I rather suspect) then he has shock protection by double or reinforced insulation, the ELCB makes no difference.

It's lacking additional protection perhaps, but that's another matter.

  - Andy.

Too many assumptions Andy/ The drill, bought from a car boot sale for little money, had a plug that was not correctly wired.

Z.

Do you mean L&N reversed Zoom? Otherwise, it never worked or would trip the VOELCB. I don't think the trip current can be anything like 500mA, because that would be useless on a slightly high Ze electrode of say 125 Ohms, giving no volts for the trip, or at least far less current. I seem to remember the coil resistance was several K Ohms, so the current might not be too far from 30mA. Anyway changing to a 30mA RCD is very cheap and easy, everything is in place for the wiring
Sparkingchip
4245 Posts
Maybe being a belt and braces man Zoomup‍ might be inclined to fit a RCD downstream of the VOELCB?
AJJewsbury
2698 Posts
A class one appliance used outdoors would give the user a 49 volt shock. Much less dangerous than line voltage, but still twice the limit of SELV.
Eh? I thought ELV was under 50V a.c. (or 120V d.c.)?
  - Andy.
mapj1
3753 Posts
With a VOELCB if the earthing is good you can get a surprisingly long way with a very badly wired plug indeed.
Silliest I have seen was green to neutral , red to earth and black to live. Worked OK apparently, until it really was plugged into an new fangled RVD, then it knocked the power off to a whole camsite.
Mike.
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3131 Posts
davezawadi (David Stone):
Do you mean L&N reversed Zoom? Otherwise, it never worked or would trip the VOELCB. I don't think the trip current can be anything like 500mA, because that would be useless on a slightly high Ze electrode of say 125 Ohms, giving no volts for the trip, or at least far less current. I seem to remember the coil resistance was several K Ohms, so the current might not be too far from 30mA. Anyway changing to a 30mA RCD is very cheap and easy, everything is in place for the wiring

David I need to clarify things as many are confused or making assumptions, although Andy is perfectly correct in what he said. The old electric drill is Class 2 plastic cased. The condition of the old installation may be very bad. The one next door of similar age was just hanging on by a thread, and when I moved the earthing lead (conductor) for inspection it just came away from the rod.

The drill was being used outside and that posed addition dangers to my mind or damp grass, possible flex damage etc.

The drill plug was showing inner worn cores outside its 13 Amp. plug. I rewired the plug for the owner and noticed that the two live conductors were reversed at the plug terminals. (I know that this makes no difference for a Class 2 appliance regarding safety).

The whole situation shouted "DISASTER WAITING TO HAPPEN"

Also, the lack of proper earthing/protection means that I can not add the new socket requested by drill man's wife.

z.

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