<P> Another cause of nuisance tripping is due to accumulated or burden currents caused by items with lowered insulation resistance . This may occur due to older equipment, or equipment with heating elements, or even wiring in buildings in the tropics where prolonged damp and rain conditions can cause the insulation resistance to lower due to moisture tracking . If there is a 30 mA protective device in use and there is a 10 mA burden from various sources then the unit will trip at 20 mA . The individual items may each be electrically safe but a large number of small burden currents accumulates and reduces the tripping level . This was more a problem in past installations where multiple circuits were protected by a single ELCB . </P> <P> Heating elements of the tubular form are filled with a very fine powder that can absorb moisture if the element has not be used for some time . In the tropics, this may occur, for example if a clothes drier has not been used for a year or a large water boiler used for coffee, etc. has been in storage . In such cases, if the unit is allowed to power up without RCD protection then it will normally dry out and successfully pass inspection . This type of problem can be seen even with brand new equipment . </P> <P> Some ELCBs do not respond to rectified fault current . This issue is the same in principle with ELCBs and RCDs, but ELCBs are on average much older and specifications have improved considerably over the years, so an old ELCB is more likely to have some fault current waveform that it will not respond to . </P> <P> With any mechanical device, failures occur, and ELCBs should ideally be tested periodically to ensure they still work . </P>

What to do when the earth leakage trips