240V earthing

Discussion in 'Motorhome Chat' started by sinbad1, Feb 9, 2009.

  1. sinbad1

    sinbad1 Deleted User

    The 240V system on the van is is basic consisting of a simple consumer unit and CB's & RCD's for the basic lighting and plug circuits +ve -ve and earth.

    With the EHU this provides continuity ie the earth is grounded at the source of supply and thats ok.

    My question is how is the system earthed? when using an onboard generator.

    regards
     
    Last edited by a moderator: Feb 9, 2009
  2. Linda and Steph

    Linda and Steph Funster

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    When I use a genny for outside performances I use an earth spike - basically a large rod with an earth cable running to an earth stud on the genny.
     
  3. pappajohn

    pappajohn Funster Life Member

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    dont forget....if you use an unearthed genny the RCD's will NOT work.

    they rely on a balance between LIVE and NEUTRAL which can only alter if theres an EARTH fault meaning something that is not normally live has become live and current will go to earth causing the imbalance amd trip the RCD.........no earth......no protection.

    as steelysteph says.....a copper earth spike and 10sqmm cable will help but it has to be driven well into the ground.
    for domestic earthing we drive a 4ft spike in with just 4" sticking out.
     
  4. sinbad1

    sinbad1 Deleted User

    thanks
    I guess the spike is really the only answer, from what i've seen i don't think many people do this or are perhaps aware.


    thanks
    You are correct the rcd's would not work quite dangerous when you think about it
    gonna need a bigger hammer:Rofl1:
     
  5. hilldweller

    hilldweller Funster Life Member

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    Just a thought......

    If the generator is on board and the there is no earth at all ( see later ) then you can't get an electric shock from live to earth.

    ( later ) But of course the earth will be connected via the plug on the genny so live to earth/chassis short inside will trip the RCD.

    Maybe it's late but I can't think of a way not having an earth spike could cause a problem with the genny on board.

    Genny outside on the ground..... With no earth you can't get a current flow from 240V to earth.

    Where does the earth go on a genny anyway ? Just to the chassis or to the neutral as in normal mains ?

    Of course the easy answer is stick an earth spike in wet ground which means you can electrocute yourself with a Live to ground short.
     
  6. shifter

    shifter Read Only Funster

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    earth spike

    In some plaises you might not get an earth withe a spike even at 4foot or more.we had to reearth our house when they replased the old mains water pipeline with plastic.could not get an earth anywhere around house with a 4 foot spike.the nie came to test the spike and could,nt believe their was no reading of it.endid up the nie got us a earth of the main over head cable.
    Had to apply for planning permision first before they did it.
     
  7. scotjimland

    scotjimland Funster Life Member

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    I think there is much misunderstanding of what earth is.. it is the center tap of the supply transformer which gives the consumer an 'earth' The Earth is not a big sponge soaking up all the stay currents going around..

    Consider an aircraft, boat oil platform or even a space craft .. they all have an 'earth' return system without having a four foot spike in the ground..

    Back to the genny, it has it's own earth return provided by the socket outlet, so the RCD WILL trip if there is a leakage back to the genny via the 'earth' connection.. nothing what so ever to do with the muddy ground outside the van..

    If you want to be absolutely safe you should bond the genny case or frame with the van, on board gennys already have this.. smaller portable ones depend on the cable.. as most suitcase models have plastic cases it would be impractical to do that.
     
  8. pappajohn

    pappajohn Funster Life Member

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    i see where you're coming from Brian,

    the genny will have an earth tag/bolt somewhere on it.

    yes....in household mains the earth does go to the neutral BUT at the local substation...not in the house.

    the ONBOARD genny should be earthed to the chassis so yes it will be earthed at the sockets/switches. i didnt read the bit about 'onboard'

    as for a stand-alone un-earthed genny on the ground......when i pitch the first thing to be done is the corner steadies......instant earth maybe a poor one but an earth non the less.

    then if it rains the tyres become an earth conductor as well, also every time you step from the van you become an earth conductor.

    then we come to the real problem. what if you use an invertor.....they have no earth at all.:Eek!:

    once saw a bloke on a JCB accidently lift a live an 11,000v mains cable.....he was told to sit still until the power was cut. if he'd stepped off he'd be dead in an instant. human earth conductor.:Eeek:
     
  9. pappajohn

    pappajohn Funster Life Member

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    so why do gennies have an earth tag on them and instructions to earth the genny to ground.....my kipor does!
     
  10. sinbad1

    sinbad1 Deleted User

    So am i right in thinking that the onboard genny earthed to the chassis would be safe provided there is some metal connection between chassis and ground only if i remained inside the faraday's cage (the van) ;but if i use 240v outside of the van it could be dangerous if or not?:Sad:
     
  11. Linda and Steph

    Linda and Steph Funster

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    My licensing authority would be rather annoyed, actually they'd shut us down, if they spotted us using a genny that didn't have an earth spike.
     
  12. scotjimland

    scotjimland Funster Life Member

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    The original question was about an on board genny ,.. it is bonded to the vehicle so it does not require a ground spike.. if a genny is used away from the vehicle as a stand alone unit and it has exposed metal parts it should be grounded with a spike to prevent any possibility of the user getting a shock from the frame.

    there is a thread here that deals with the question ..
    IET Forums - Horsebox to be wired for 230v
     
  13. sinbad1

    sinbad1 Deleted User

    Your right Jim my original question was regarding onboard gennies ;but i guess if its onboard or standalone outside does bring up some confusing issues.

    if as you say stand alone metal gennies should be grounded by a spike, then surely earthing the onboard metal genny to the chassis would only be an extension of its metal case so could be more dangerous if outside using 240V?

    I still believe some kind of grounding between onboard genny, beit to chassis then a spike is the safest option, unless your in a thunderstorm:Eeek:

    RCD's Not sure how or if they are effective in a groudless situation, just don't want to be a human conductor :Rofl1:
     
  14. hilldweller

    hilldweller Funster Life Member

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    Easy enough to find out - press the test button.

    Being fearless I would get a small lamp, stick one wire in the Live somewhere and jab the other to chassis or earth. The breaker should trip.
     
  15. Linda and Steph

    Linda and Steph Funster

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    Oops :Blush: another case of me not reading the question properly :Blush:
     
  16. sinbad1

    sinbad1 Deleted User


    Hey never thought about that can i borrow your wellies:Rofl1::Rofl1:
     
  17. hilldweller

    hilldweller Funster Life Member

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    Wellies ?

    I wear a Faraday cage, except when in the bath.
     
  18. Linda and Steph

    Linda and Steph Funster

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    That's a bit personal :Wink:
     
  19. olley

    olley Funster

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    Hi I think you are worrying un-necessarily, here is my understanding of the situation.
    With household electrics sockets you are looking at an almost unlimited momentary amperage before a fuse blows, that's why RCD's are so essential, and its the amps that kill you, with a 1000watt genny only about 4amps, so it will make you jump but its unlikely to kill you.

    That's why you can have a shaver socket in the bathroom, your protected from the household mains by a mains isolating transformer, its still 230v but at a much lower amperage so is considered safe.

    Olley
     
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  20. smifee

    smifee Read Only Funster

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    my head hurts
     
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