110 - 240 volt conversion

Discussion in 'American RV's' started by tonatcher, Apr 8, 2009.

  1. tonatcher

    tonatcher Read Only Funster

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    Hi
    This is my first post on forum, so be gentle with me !!!!!

    I'm in the process of converting our Leprechaun for 240 volts. I intend to put just one UK double socket for the odd bit of kit that is 240 only and keep the present 110 sockets for modern 110-240 appliances.
    Instead of using a yellow auto transformer(which only has one winding and the potential in fault conditions to apply 240 volts to the output) I have a 3.5kva isolating transformer(primary 240 secondary 110). This will feed the existing breaker box along with 110 volt generator to power roof A/C, fridge, battery charging and 110 domestic sockets (microwave has been changed to a new UK one).
    My problem is this transformer has the centre tap of the 110 secondary connected to earth so output legs are both at 55 volts above earth, and I not wanting to damage the A/C, or anything else, don't know whether to leave it like this or disconnect this earth ????
    I have looked around the forum, but cannot find a similar query.
    Any advice would be appreciated
    KIND REGARDS
     
  2. scotjimland

    scotjimland Funster Life Member

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    Hi

    Sorry for not replying sooner but I wanted to check my tranny wiring first..

    It is a 3kva site tranny with separate primary and secondary windings.. it's not an autotransformer type.

    On the 110v side it has 55 - 0 -55 v .. the centre tap is earthed .. the genny feeds this side via a relay controlled by the EHU supply , this prevents both feeding the tranny at the same time and the EHU plug from being live while running the genny ..

    hth

    Jim
     
    Last edited: Apr 9, 2009
  3. tonatcher

    tonatcher Read Only Funster

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    Hi, Jim
    That sounds exactly the same as I have, with the relay switch for the gennie and shore power. My real concern is how my aircon and fridge will react to the central earth.The last thing I want to do is damage them and then have the problems of getting replacements or spares from the US because I made a silly mistake. The Americans earth their neutral I believe !!?? so the units may or may not get only 55 volts or much more.

    As I see you are major contributor to this forum, on the lighter side we bought our leppy last year in Texas and drove it over to Brunswick and RoRo'd it to the UK.We took three weeks to drive it there, and eventualy got it home from Pompey, and then realised we should have kept it in the US longer,meanwhile our daughter was in the LA getting her commercial pilots ilcence. So we went to see her later in the year and the day before we were due to leave her FAA examiner said his neighbour was trying to sell his C class( a 1985 34ft Pace Arrow, his pride and joy, that he had owned since new, had workshop maintained, and because he was 87 he thought he could no longer cope with it) it is in A1 condition and I gave him what he asked for it on the spot--£4,000 !!!!
    So in the next few weeks we are going to move it (Harvey) to our friends home in Alabama and create a base for the family (and us ) to explore the US properly
    We are no spring chickens, but, thankfully still alive.

    To go back to the main subject - will my aircon and fridge work.

    Many thanks for your trouble and kindest regards

    Tony and Cheralyn
     
  4. scotjimland

    scotjimland Funster Life Member

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    Hi Tony

    Mine has been fine, but if you want to be absolutely sure,( it's worth checking anyway), switch off the 110v MCBs for the fridge and aircon and check the voltage at the board. Alternatively, unplug the fridge and check there.

    We would love to tour the US but for the present will have to stick to Europe, we still have lots to see and explore..

    Exciting times ahead for you and family in the US :Smile: Good luck and safe travels, let us know how you get on..


    Jim
     
    Last edited: Apr 10, 2009
  5. tonatcher

    tonatcher Read Only Funster

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    Hi Jim
    Not only "cooking on gas" but now cooling on electricity. Tranny worked fine once I had the confidence to load it, knowing that yours worked.
    Using an in line adaptor on the 240 side I read(ignoring power factor) :-
    Tranny only 90 watts
    Fridge/freezer +300
    A/c fan only +150
    A/c cooling +700
    This left me to investigate the only other,I think, permanent 110v load, the leisure battery charging(which load must be deducted from the above).I'm on a Ford E350 chassis, which I have a handbook for, but the coach has an extra box of tricks under the hood with lots of heavy battery connectors and a strange looking cylindrical unit labelled a BD relay, which operates when I press the battery disconnect in the rv's entrance.
    If I dis the leads of the leisure battery and voltmeter across the leads I have 12.5v dc, which is coming from the 110v supply, and I assume is the charging voltage ?? !!, not what I would call a satisfactory charge voltage--am I missing something else??

    Kind regards
    Tony
     
  6. scotjimland

    scotjimland Funster Life Member

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    Hi Toni

    The BD (battery disconnect) relay isolates the house batteries .. as you already discovered by pressing the control box, this will also auto disconnect if the battery voltage drops below 12v in order to prevent total discharge and possibly damaging the batteries

    USRVs don't usually have decent chargers, merely a 110vac - 12vdc power pack that doubles up as a charger. It either cooks the batteries if left on all the time or doesn't charge them properly.. many owners, including myself, fit a decent 230v three or four stage automatic charger .. but you need to check first, it may already have a decent charger..

    hth

    Jim
     
  7. Glennt

    Glennt Read Only Funster

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    The Best voltage for USRV

    Like so many RV'ers we all make do with a basic transformer to drop the EU voltage down to 110-120v this is fine to a point but when you start doing a bit more investigation you realise that it's not the voltage that is the all important factor here but the Hz, products that were produced in the USA have been made to work on 60Hz and not 50Hz which is what is available in the EU. Yes most items appear to work OK with just the voltage being converted but the truth of the matter is that items such as Air con, Washing machines, microwaves, water haters to name but a few will get very hot and not work properly at the wrong frequency in some cases a fire could develop and you will drastically reduce the life of the product.

    So why do we fit these micky mouse step down transformers? because there isn't a product out there that changes both the voltage and the Hz. OR IS THERE.

    Check out this product made specifically for the EU RV'ers
    RV Transformers
    This is the answer if you want to do the job propely and sleep easy at night.
     
  8. bashers

    bashers Read Only Funster

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    This 240/50Hz to 120V/60Hz converter does not do "step up" so you have to find yet another solution when you use your 120V generator to power your EU appliances
    possibly by driving all 240V appliances from an inverter?
     

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