TRUMA Series 3 Ultra Store Water Heater - Tripping Caravan RCD As Soon As Switched On

[truckin73]

Hi,
My TRUMA Series 3 Ultra Store water heater keeps tipping the caravan RCD as soon as unit switched on, following filling up with water.
Is this a classic case of the heater element having failed and if so, is there any way to prove this is the case before buying a new element.
Thanks.

 

[Damian]

Yes it is a case of the mains element having failed.
Switch off the circuit breaker to the heater, apply power to the van, and having filled the heater with water, switch on the heater circuit breaker,if it throws the trip,it eds a new element.
Or,trace the wire from the heater to its plug connection ,about half a metre away, disconnect and with no power to the van, measure the resistance of the element, if you get a 0 reading it has failed.

 

[Afyfe]

A RCD device will only operate if there is an earth fault.It measures the current in each pole - in this case line and neutral and if the current value (amps) is not the same in each pole the RCD device will trip.
From your description the element must be touching earth somewhere with the water being the conductor and some of the current is leaking to earth causing the amps in each pole to different and creating an unbalance in the RCD device
It is still possible that the heater element is intact (not broken) in which case you could still measure a resistance between the Line and neutral connections of the element.
A broken (open circuit ) element will not trip an RCD device - only an earth fault will.
The heating element probably has a metallic outer sheath directly in contact with the water and the outer sheath has probably corroded rather like a domestic kettle.

 

[waffler]

Most probably is the heater. When it failed the wire broke and is possibly touching the element case so shorting it out. Maplins sell a voltmeter that reads resistance as well. (£5) Switch off mains, disconnect heater from mains and use meter to read resistance between red and brown leads. If it reads 0 the heater has gone. Sorry if my instructions are pedantic but most folks assume every one knows how to do it-.