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Static Caravan Problems.

Zoomup
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
    I got lost around when you mentioned 100mA. Is this an existing device, or is it a proposal to install one to reduce nuisance tripping?
  • 0
    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

    Yes - you always need timedelay on any upstream RCD to achieve discrimination - as  Reg 536.4.1.4 etc. tries to say (but probably with far too many words).


    To my mind the ratio of the residual ratings should ideally be 3:1 not to highest rated downstream device, but to the sum of the downstream devices.


      - Andy.
  • 0
    What is actually tripping? You say there is a 30 mA RCD in the van and in the pitch hook up point is it both of these or just one?  Or was it one of the MCBs? If it was then yes that points to an overload  16 amps seems a bit stingy and with a few electric heaters and suchlike its easy to exceed that. Finally where is this in the country I know of one caravan site that has big supply problems due to an undersized  pole pig. Sorry zoomup I not trying to teach you how to do fault finding i could of worded it better
  • 0
    AJJewsbury:
    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

    Yes - you always need timedelay on any upstream RCD to achieve discrimination - as  Reg 536.4.1.4 etc. tries to say (but probably with far too many words).


    To my mind the ratio of the residual ratings should ideally be 3:1 not to highest rated downstream device, but to the sum of the downstream devices.


      - Andy.


    So, the Fig. 7.1 illustration should have the words "Time delayed" added to the 100 mA R.C.D. that supplies 4 caravans, in Guidance Note 7, Special Locations.


    Z.


  • 0
    Kelly Marie Angel:

    What is actually tripping? You say there is a 30 mA RCD in the van and in the pitch hook up point is it both of these or just one?  Or was it one of the MCBs? If it was then yes that points to an overload  16 amps seems a bit stingy and with a few electric heaters and suchlike its easy to exceed that. Finally where is this in the country I know of one caravan site that has big supply problems due to an undersized  pole pig. Sorry zoomup I not trying to teach you how to do fault finding i could of worded it better


    I suspect overloading myself on this Norfolk site. The customer can not remember exactly what tripped off, but all is reset and is on now. Some sites are downgrading to a 10 Amp. per pitch supply from the traditional 16 Amp. supply. The site electrics used to be purely for touring vans, but now are for statics. I wonder if the electrics have not been upgraded to allow for this as tourers usually demand less electricity, a battery charger, t.v.,  heater and a kettle maximum.


    Z.


  • 0
    wallywombat:

    I got lost around when you mentioned 100mA. Is this an existing device, or is it a proposal to install one to reduce nuisance tripping?


    The 100mA R.C.D. supplies 4 individual pitches maximum, each with a 30mA R.C.D. per pitch. So up to 4 caravans run through one 100mA R.C.D.


    Z.


  • 0
    16 amps should suffice for a TOURING caravan with modest loads and LPG for heating and cooking.


    16 amps is almost certainly very inadequate for what is in effect a full time home or a holiday home with the usual appliances including electric heating. The reported three space heaters are probably very roughly 30 amps in total. No diversity allowable for space heaters as simultaneous operation is expected in cold weather.

    30 amps will trip a 16 amp MCB in "not long" no great accuracy may be claimed in this as the exact load is not known.


    To this estimated 30 amp heating load should be added a nominal 2 amps or so for lighting and small appliances, and say 15 amps for the kettle and one other appliance such as microwave oven, coffee machine or the like.

    A 32 amp supply would be marginal with that load, and 16 amps no way.


    And even if the problem IS earth leakage, then on rectifying this, overload tripping seems almost certain.


    A larger supply or changing the heating to LPG seems to be required.


    BTW, I recently wired a mobile home for a neighbour.  4 circuits 

    1) 4 amp lighting.

    2) 4 amp numerous general use 13 amp sockets for low loading appliances.

    3) 4 amp, water heater, 750 watts.

    4)  16 amp feeds a 3 position manual changeover switch which is connected to 3 of single 13 amp sockets but only to one such socket at a time.

    The three switch positions are marked

    "kettle" about 10 amp loading.

    "space heater" 10 amp loading

    "other" For use of power tools, hair dryer, or cleaning equipment.


    Significant overloading of a 16 amp supply is thereby prevented and reasonable use of most appliances is allowed.

  • Former Community Member
    0 Former Community Member
    Apparently the electrics were reliable before the van was moved to a new pitch on the same sandy site.


    It could be something as simple as the new pitch location (sandy or not is irrelevant) being nearer to the incoming DNO supply point and thus having a greater voltage at source and thus a greater current draw on the resistive loads.


    Plus, if the user can be believed, the use of LPG is rare on all the sites I've inspected where the electric, metered or not, is available. Who wants to lug around a propane bottle?


    If the two 30 mA RCDs were tested and that the  100 mA "locked away" RCD didn't trip, it is almost certain that the 100 mA device is time delayed, or faulty.


    Regards


    BOD
  • 0
    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.
  • 0
    Could easily be a staple through a cable from when it was built in the factory, along with those heaters.

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