Mains electricity through motorhome chassis

Discussion in 'Tech/Mech General' started by veevee, Jul 21, 2016.

  1. veevee

    veevee Funster

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    Our motorhome is parked up and plugged into power, all 240v devices are working correctly, no apparent problem.
    This afternoon was checking tyre pressures and picked up a small shock off of a steel wheel rim, first for me getting a static electricity shock from a vehicle chassis. While adding air and checking tyre pressure again received more shocks but they increased in power and were becoming quite sharp.
    One shock was a little like the shock (I think 60v) from a phone line, well it was 35 years ago anyway. So decided to try to measure if there was any AC power through the wheel rim, it measured 80v.
    Got wife to switch the mains off and the reading dropped to 18v, switched on again back to 80v.

    So a question. Is there a shortcut to where to start looking for the problem or is it a case of starting at the 240v input socket and going through everything from there?

    I was involved with general vehicle electrics for 20+ years with own garage workshop and have rewired a couple of houses, but wouldn't call myself an electrician.

    Any help gratefully received
     
  2. Gromett

    Gromett Funster

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    Isolate each circuit in turn. My van has two breakers which would cut the search in half. after that it will require disconnecting wires.. Good luck.
     
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  3. veevee

    veevee Funster

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    Good idea, we have 2 breakers too, thanks Gromett
     
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  4. Flamenca

    Flamenca Funster Life Member

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    The 'mains' supply should be completely isolated from the chassis.
     
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  5. mitzimad

    mitzimad Funster

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    did you have anything in the van running on 240 as it could be an earth fault on that
     
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  6. veevee

    veevee Funster

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    Yes, the charger in the Elektroblock only
     
  7. veevee

    veevee Funster

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    Thank you Flamenca, I realise that but something is passing current to earth and mitzimad's suggestion above may be the worst thing for it to be. It's raining hard here for the next 2 days so maybe as the MH is outside I'll leave the testing until Sunday or Monday.
     
  8. Tootles

    Tootles Funster

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    Just had a trawl online. It seems the Elektroblock units suffer from poor or faulty earth connections. In effect, your becoming the earth for the unit. Now I dont know how these units are wired, or if in fact they are earthed to the chassis??????????? Could there be a possibility that your EHU earth is faulty, either cable, at the van, or even the house??
     
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  9. veevee

    veevee Funster

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    I guess any of that is possible, this may be a long process and thanks for checking all that out. I'll check which circuit the problem is on first or if it's one or both, then go back initially to the EHU supply socket and so on. I do have the Hymer wiring diagram so can study that while it rains.
     
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  10. Bobby22

    Bobby22 Funster

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    Why would you still get 18v when disconnected from mains????

    Battery charger? Common with AC and DC circuits?
     
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  11. Tootles

    Tootles Funster

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    Or a leak from an inverter??
     
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  12. veevee

    veevee Funster

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    No inverter, no aircon, no fans, no 240v oven or microwave, no tv, just the basic MH as it came in the standard form a 2006 Hymer B680 Starline comes in. There are 3 extra plug sockets but with nothing plugged into them.
     
  13. jonandshell

    jonandshell Funster

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    Any earth leakage should be detected and isolated by the RCD.
    It sounds like that should be checked for correct operation first and foremost.
     
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  14. jonandshell

    jonandshell Funster

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    Out of interest where did you place your probes when measuring the AC voltage?
     
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  15. mitzimad

    mitzimad Funster

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    to get 18v without ehu connected you must have solar running? sounds like its an earth problem from the electroblock and the voltage increases when ehu is on
     
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  16. emmitdb

    emmitdb Funster

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    I had a similar problem last year when on hook up. I used the steadies to earth the van before I touched it.
    Those very nice people at 'VanBits' talked me through checking.
    (Assuming your RCB's are not tripping?)

    Check the plug on your cable that plugs into the mains. You are checking to see if the Earth is connected properly.
    If that is OK, check the plug that goes into the 'van, (assuming you are using a single cable and not as reel with a spur on it). Again see if the wires are connected properly and securely.
    The next to check on the 'van where the cables are attached at the rear of the input socket where the electricity enters the vehicle.
    Here's the words of VanBits.
    "If it's all OK up to there then you need specialist help"

    I was OK because I found one of the Earth connections on my Hook Up cable were hanging on by just a thread or two. On rewiring the plug, everything returned to 'Normal' whatever that means. Good Luck.
     
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  17. veevee

    veevee Funster

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    I thought about it all overnight and came to the same conclusion of checking the input into the MH first, but as it's tipping it down at the moment and the ground is very damp will leave that for a couple of days.

    + to the wheel rim and - to the ground the MH stands on. It's a thin layer of gravel with soil underneath


    no solar fitted yet but that's an interesting point of a residue 18v with the EHU disconnected.


    After some basic checking this may be the route I'll take but will test first. I do have another 2 EHU leads so swapping them may prove something to start, then the plugs and sockets.

    Thanks to everyone, I'll certainly report back with whatever result I find, all this may be helpful to others.
     
  18. Wagoneer

    Wagoneer Funster

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    I've used a mains tester which plugs into a standard 240v socket. Mainly got it to test for reversed polarity but has been handy for checking the EHU cable. It checks for No Neutral, No Earth, Live/Earth reversed and Live/Neutral reversed.

    Can also be used to check campsite bollards with suitable adaptor.
     
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  19. veevee

    veevee Funster

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    Wouldn't have the make/model/price and where from would you WA? Thanks
     
  20. Wagoneer

    Wagoneer Funster

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    Mine is from W4 http://www.w4limited.com

    Cost £9.98 but available from most Caravan outlets.
     
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