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V.O.E.L.C.B.

Zoomup
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.


  • 0
    What is the tripping current of a Voltage Operated Earth Leakage Circuit Breaker?
  • 0
    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.


  • 0
    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.


  • 0
    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.


  • 0
    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.


  • 0
    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.

    2927c3c3ff70925b72ae168f7e93a33b-original-437296f1-1ebc-4cdb-b526-6d5b47ecbeb1.jpg

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    1109469dec0bac670c87f6a3b7c71877-original-11910edc-753f-4a5d-95ac-101f4501004c.jpg
  • 0
    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.
  • 0
    ca609695175a58107ce6b72a6cec2ee2-original-447fcdf7-1eda-4de4-b5d3-19d93e5120ea.jpg
  • 0
    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.

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