Reverse polarity

Discussion in 'Motorhome Chat' started by mojo, May 13, 2014.

  1. mojo

    mojo Funster

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    Just spent two nights on a marina campsite in Uphill,Somerset.With the mains plugged in our Sargent supply unit showed up a red light stating reverse polarity.When this happens abroad I use a extra plug that has the wires reversed to bring the supply to normal and the light expires.
    On this occasion it remained on ?

    Now on a new campsite and all is back to normal.

    Does anyone understand what was happening on that one particular campsite ?
     
  2. JeanLuc

    JeanLuc Funster

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    Could the warning have been caused by a bad earth connection?

    I have to say I don't bother about reversed polarity but I usually put a socket tester in the van to check for poor earth.
     
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  3. Traveller_HA5_3DOM

    Traveller_HA5_3DOM Read Only Funster

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    I have yet to see a camper that has switches on the 13 amp sockets so even with normal polarity the live wire follows right down to your appliance switch. It does stop there but when reversed polarity the whole appliance is live right round to the on off switch. Does it matter? Not if the appliance wiring does not touch something that you can touch in handling it. i.e. it is faulty in some way. The main risk in single live switched sockets as we use in the UK or indeed non switched sockets that campers use is that the plug wiring remains live as long as it is plugged in, so wiring breaks due to the flexing and general handling of the plug can result in you touching live wires.
    Does anyone have switched sockets in their motorhome fitted as standard?
     
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  4. NickNic

    NickNic Funster Life Member

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    Mine does :Cool:
     
  5. 1_man_and_his_dob(lo)

    1_man_and_his_dob(lo) Funster

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    Yes...one double socket and a single.
     
  6. camocam1

    camocam1 Read Only Funster

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    No switched plugs but I bought switched adaptor for the plugs so we can switch off items if required
     
  7. aba

    aba

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    At a venue we have done several concerts at the audio mains supply is transformer isolated that brings on all sorts of lights on the distro.

    Don't understand how it works but it seems to ok.
     
  8. pappajohn

    pappajohn Funster Life Member

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    agreed.....this also happens a lot when using a generator.

    The normal polarity circuit needs a proper earth and as the generator doesnt have a true earth so sees it as reversed polarity.

    insufficient or complete lack of earth is FAR more important than reversed polarity for two reasons.

    1...it protects you in an earth fault situation.....it cant if theres no earth

    2...protective devices (RCD/RCBO) rely on an earth to work....it cant work if theres no earth.
     
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  9. gasman2008

    gasman2008 Read Only Funster

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    English MCB's are on the live circuit, RCD's are on both live and neutral, so if you have reversed polarity, your MCB is not working if you have a short to earth even if it is through you to earth, the RCD may still protect you but not always. If you use your home with reversed polarity you have removed one safety device. For that reason I always deal with the situation using a changeover lead I made. I don't know for sure as I have not worked in France but I have been told that their MCB's work on both live and neutral so reverse polarity not so important, but I take no chances.
     
  10. pappajohn

    pappajohn Funster Life Member

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    alternating current (AC) spends 50% of its time reversed anyway.....

    230v+ / 0v / 230v- / 0v / 230v+.....60 times a second
     
  11. SMB

    SMB Funster

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    I have the Sargent control box in my Swift and the reverse polarity light comes on for that and also no earth. I have a tester which plugs into the internal plug sockets and gives a indication re the electricity supply i.e. no earth etc. Van hasn't blown up yet fortunately...:BigGrin:
     
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  12. Clive

    Clive Funster Life Member

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    You get the same issue with a generator and, so I've been told, it's a lack of earth point that causes it.
     
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  13. gasman2008

    gasman2008 Read Only Funster

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    This is not how ac works neutral is just that neutral, the live goes 120 above neutral then 120 below 60 times a second. At no time is any current carried along the neutral. In fact in a PME earth system the earth and neutral are linked.
     
  14. pappajohn

    pappajohn Funster Life Member

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    i wondered how long it would take !!!!!!
    Just under 2 hours :Rofl1:

    I work with the stuff for a living. :thumb:

     
    Last edited: May 13, 2014
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  15. Techno

    Techno Funster Life Member

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    They are only linked at source before the RCD or RCBO
    If you put the neutral to earth or anywhere else outside of the circuit it will immediately trip the device. The most important thing is to test the device operates every time you set up somewhere new. Polarity is irrelevant unless you're going to open things up and meddle with live wires.
     
    Last edited: May 13, 2014
  16. Voyger1010

    Voyger1010 Funster

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    If it was a marina that you were camping at, and using their EHU , then it is probably an earth fault. Marinas are renowned for the problem with the main electric supplies and poor earth connections. In a number of marinas I have visited over the years with the boats there has been this problem which also causes galvanic corrosion via stray electrical currents.
    Given what you've reported, when you got back to your normal site hook up and that all was well, I certainly would worry about reversing polarity devices. Hope it helps:Smile:
     
  17. scotjimland

    scotjimland Funster Life Member

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    first of all, the frequency in the UK is 50hz.. not 60

    and the neutral conductor in an AC circuit carries the exact same current as the live ..

    if you don't believe, me try a tong tester on your Live and Neutral on your domestic supply ..

    if that was imbalanced it would trip the main ELCB

    NO current flows in the Earth unless their is an earth fault .. which as said.. would trip the ELCB
     
    Last edited: May 13, 2014
  18. Puddleduck

    Puddleduck Funster

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    Okay, continuing with the thread I've been told that we have a double pole (I think - it was getting a bit too technical at this point) MCB and were told that protected in some way. Is this correct and we don't have to worry about reversed polarity?
     
  19. JeanLuc

    JeanLuc Funster

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  20. andy63

    andy63 Funster

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    hi puddleduck, I think the reference to double pole just means the switching isolates both the live and neutral lines at the switch..
    it seems to be generally agreed that as long as you are not going to be working on live appliances in your motorhome then its not really an issue.
    I run a generator to charge my batteries and the tester would indicate a fault but all works ok.
    discussions on the subject always get quite technical :BigGrin: but I always enjoy reading peoples views on the subject.
    regards andy
     
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