charleydog Posted August 22, 2019 Share Posted August 22, 2019 In my 250volt control unit there is a circuit breaker with a plunger which says test monthly. what should happen when I do . pressing it when connected to the mains of course,does nothing,is this correct? Link to comment Share on other sites More sharing options...
BruceM Posted August 22, 2019 Share Posted August 22, 2019 Assuming that the circuit breaker is set (ie you have 240v at the van’s plugs), then I would expect that pressing the ‘plunger’ will cause the circuit breaker to activate, cut the 240v supply to the van’s plug sockets and require the circuit breaker to be reset before power can be restored. Link to comment Share on other sites More sharing options...
charleydog Posted August 22, 2019 Author Share Posted August 22, 2019 Thanks for the swift reply Bruce.Ordered a new one, Link to comment Share on other sites More sharing options...
Alanb Posted August 22, 2019 Share Posted August 22, 2019 charleydog - 2019-08-22 4:16 PM In my 250volt control unit there is a circuit breaker with a plunger which says test monthly. what should happen when I do . pressing it when connected to the mains of course,does nothing,is this correct? The circuit breaker to which you refer is the Residual Current Device or Residual Current Breaker , commonly abbreviated to RCD or RCB. If an RCB does not trip when the test button is pressed, with mains supply connected then it must be assumed to be faulty. If the RCB is faulty, then you are at increased of a possibly fatal electric shock, in the event of an electric fault occuring within the vehicle. I strongly advise that you have the RCB replaced, or at least checked by a competent person. A RCB works by comparing the currents flowing in the live and neutral conductors, which should be the same. If the imbalance is greater than 25mA, (25/1000A) it should trip. The test button creates a similar imbalance within the circuit breaker. Many homes now have these devices fitted, particularly in the supply to the electrical sockets and showers etc. While we should test them regularly, it does not always happen due in part to the need to reset the time on microwave ovens etc. Alan Link to comment Share on other sites More sharing options...
Derek Uzzell Posted August 23, 2019 Share Posted August 23, 2019 charleydog - 2019-08-22 6:48 PM Thanks for the swift reply Bruce.Ordered a new one, You are certain that the present RCD is not functioning? There seems to be no standardisation regarding the size, position or colour of the RCD’s test button and - although the button on many RCDs is large and prominent - the test button on my Rapido is very small and not that easy to depress. Link to comment Share on other sites More sharing options...
colin Posted August 23, 2019 Share Posted August 23, 2019 The last time we had a similar problem on a house it was a short from neutral to earth. RCDs rarely go wrong, but not unheard of. Link to comment Share on other sites More sharing options...
Alanb Posted August 23, 2019 Share Posted August 23, 2019 colin - 2019-08-23 1:13 PM The last time we had a similar problem on a house it was a short from neutral to earth. RCDs rarely go wrong, but not unheard of. Charleydog, the OP, queried the fact that the RCD in his motorhome did not trip when the test button was pressed. An internal neutral to earth fault will result in some current bypassing the neutral side of the RCD. When with increasing load, this imbalance exceeds the RCD threshold (typically 25mA), the RCD should trip. I would not expect a neutral to earth fault to cause the RCD to fail to trip unless current was flowing from the supply neutral into the domestic earth, and partially balancing the current applied via the test button. This situation is not impossible, particularly with overhead distribution, and the earth being a ground rod at the premises. However in these circumstances nuisance tripping could occur, when no internal loads are connected. Alan Link to comment Share on other sites More sharing options...
charleydog Posted August 24, 2019 Author Share Posted August 24, 2019 Thank you all for your knowledge and explanation of the problem. I have changed the r.c.d and all is as it should be. I am in fact, about to trade this camper for a AS Warwick XL but did not want too in any less than perfect order, so thanks again all :-D Link to comment Share on other sites More sharing options...
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