When do the Nuisance Trips Happen with the Earth Leakage Circuit Breakers?

Nuisance trips can take place when there is an installation with two connections to the earth. Whenever there is any high current striking near by it can cause a voltage gradient in the soil which in turn provides the ELCB with enough voltage causing it to trip.

Whenever the rod used in the installation is placed close to any earth rod of adjoining building, the leakage in the earth in the neighbouring building can also raise the ground potential and in turn cause a huge difference in voltage between the two earths. This also causes the ELCB to trip. Such occurrences do not happen often but are encountered at times which close earth rods which are unsuitable for the ELCBs are used of the installations.

Nuisance trips are at times caused even from normal and harmless currents or earth leakage happens to an extent. Nuisance trip are more often seen in the RCDs rather than in the Earth Leakage Circuit Breakers.

One of the major causes of nuisance trips is due to the accumulated currents which are caused by the installations which have a low insulation resistance. This can happen if the equipment is older or can also take place in equipments which have heating elements or can also occur in the wiring in the buildings which are longer damp as well as rainy climatic conditions. The resistance can lower in such cases due to the tracking of the moisture. If the device which is used is 30 mA and if the burden from the various sources is 10 mA then the ELCB unit would trip at 20 mA. The individual appliances in this case are safe and out of risk but such occurrences will reduce the tripping level of the unit. Such problems were majorly seen in the old installations where a single Earth Leakage Circuit Breaker was used for the protection of multiple circuits. Many of such are now replaced with the RCDs as they provide more protection to the appliances but the RCDs are more often seen to suffer in cases of false trips. 

There are also occurrences when there is a passage of fault current which is not sensed by the Earth Leakage Circuit Breaker, but the operation of the ELCB is never compromised. The ELCB just does the same by preventing the earth metal work to rise due to the dangerous voltage conditions.