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Static Caravan Problems.

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I was called out to a static holiday/residential caravan today. Nuisance tripping was reported. Apparently the electrics were reliable before the van was moved to a new pitch on the same sandy site. The van's consumer unit comprises 1 30mA R.C.D., a 32 Amp socket M.C.B. and a 6A lighting M.C.B.


The pitch permanent "hook up" point comprises a 30 mA R.C.D. and a 16 Amp M.C.B.


The lady has many high powered appliances, 2kW kettle, three 2kW+ room heaters, a 2.2kW coffee machine etc. The heating is normally by bottled gas.


The two R.C.D.s tested out fine, not over sensitive. But the van owner can not remember which devices tripped off over a period of time. Once the nearby brick supply building had to be accessed to reset something, but we were not allowed even just to look inside it today by the site owners. Very unhelpful.


Anyway, all appliances tested good, no faults. I presumed that the lady had plugged too many items in at once.                                                                                                                                                                                                                                                                Guidance note 7, page 58 Fig. 7.1 it shows 4 possible separate vans being supplied via a single  100 mA R.C.D.


So, looking at the possibility of nuisance tripping if 4 vans each leak say 20 to 30 mA, the 100 mA R.C.D. could trip off blacking them all out. Should a time delayed 100mA type be used? The Guidance note says that the 100 mA R.C.D. is chosen to discriminate with the pitch socket outlets R.C.D.s. But, if say 100mA was to flow from a van fault,  both the 30mA pitch socket R.C.D. AND the 100mA brick supply building could trip off together. This would then deprive a total of 4 vans of a supply.


Comments please.


Thanks,


Z.


  • 0
    Sparkingchip:

    If you did a 5x test and sent 150 mA to earth without tripping the the upfront RCD then as Bod says it’s either time delayed or faulty, alternatively it is 300 mA, an ELCB or doesn’t exist.


    A 30 mA test will often take 100 mA RCD out if it’s not time delayed and the test button on the 30 mA RCD can take both of them out.


    The tests were a 1/2 and 1X test, as I wanted to lessen the risk of taking out the inaccessible R.C.D., if there is one, in the locked brick supply shed. I was more interested in checking over sensitive R.C.D.s at the van hook up and inside the van. They both tested o.k. for functionality.

     


  • 0
    Morning all how's it going? Sparkingchip i thought an ELCB was an RCD by another name? Or am I wrong?
  • 0
    ELCB is indeed generally an older term for what we today call an RCD.


    Two types of ELCB existed. Current operated types measured the current in the live and neutral conductors and tripped if these were not very nearly equal. They had four connections, live in and out, neutral in and out. Still used today and now known as an RCD.


    The other type was a voltage operated ELCB. This measured the voltage between the E terminal connected to an earth rod, and the F terminal connected to the installation  earth wires. If this voltage exceeded a certain figure they tripped.

    They had six terminals. live in and out, neutral in and out, E and F.

    Obsolete. Vulnerable to parallel earth paths such as a metallic water pipe that was connected to the F terminal via the CPC to a water heater.

  • 0
    Kelly Marie Angel:

    Morning all how's it going? Sparkingchip i thought an ELCB was an RCD by another name? Or am I wrong?  


    Hello Kelly, an E.L.C.B. is an earth leakage circuit breaker. Here is a JW video about the now obsolete Voltage Operated Earth Leakage Circuit Breaker (V.O.E.L.C.B.).


    They normally tripped well before the installation earthed metalwork reached 50 Volts, say at 30 to 40  Volts max.


    The earthing lead and rod were essential to proper operation. The rods sometimes rotted away or the earthing lead was pruned through thus making the device useless. I still find working models installed but they are getting rarer nowadays.


    A family were receiving shocks from installation metal work in an old holiday chalet here. The V.O.E.L.C.B. had no reliable connection to its earth rod, so thus did not work. Very dangerous.

    https://www.bing.com/videos/search?q=youtube+JW+VOELCB&docid=608039490843982793&mid=E9C7C600CA59C2530BDFE9C7C600CA59C2530BDF&view=detail&FORM=VIRE



    Edit. Add, What JW fails to say is that if the very long metal undergrounf water pipe is connected as his diagram shows the 15 Amp immersion heater fuse will automatically blow thus quickly clearing the fault. The V.O.E.L.C.B. will still limit the installation Voltage to less than 50 Volts in any case.


    A big fault with them was that a fault next door causing a water pipe to reach say 3o to 40 Volts would trip off your V.O.E.L.C.B. which would be a nuisance.


    If the earth electrode was not positioned out of the resistance area of other buried metalwork say like the underground metal water pipe, the coil would be effectively shorted and would not detect the fault Voltage of up to 50 Volts.


    One good thing about the design of the V.O.E.L.C.B. was that the test switch confirmed the good condition of the device plus the earthing lead and earth rod as well. A break in the connection to the earth rod would not allow the device to trip if the test button was pressed with the Crabtree design.


    Z.


  • 0
    Thanks guys for the explanations  I got it now
  • 0
    The big black VOELCB with the yellow test button is easy to spot as are most RCD devices. 


    However there's some hybrid devices, RCDs made up using a VOELCB.


    Try this one from Wednesday in Devon, VOELCB or RCD?
    c5f8551222043d37eb68e524b00878e2-original-20210424_213426.jpg

  • Former Community Member
    0 Former Community Member
    I'm going for 500 mA RCD in there Andy!


    Regards


    BOD
  • 0
    Today I tried testing the RCD and at 30 mA it failed to trip, at 150 mA it tripped in 8.5 milliseconds,  this was the point I checked what it said on the RCD. 


    I had already realised there's issues with the CU but had only glanced at the RCD. 


    There's not actually many electrical installations on the UK with adequate RCD protection. 

    235f295dc6f9b6c00175ddb03f7e237f-original-20210424_125246.jpg

  • 0
    perspicacious:

    I'm going for 500 mA RCD in there Andy!


    Regards


    BOD


    Quite possibly, I tried it at 30 mA and 150 mm without getting it to trip, so I fitted a double pole B40/30 mA RCBO to the shower circuit and wrote an advisory note.


    It is earthed TNCS-PME.


  • 0
    91f336dee0d852dcea5c7e59286acdea-original-20200728_110719.jpg


    One in South Wales from last year I posted a picture of before on this forum. 


    The label on it says it’s a 0.5 amp RCD, just as Bod said.


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