Random earth leakage problem

[Dave A]

Has the earth leakage unit in the house been replaced?

Nuisance earth leakage tripping sure is a PITA. Part of the problem is the fault that is causing the tripping never gets enough juice to really advertise where it is while on the earth leakage unit. My sparkies use the term "blow the fault clear." It involves taking the suspect circuits off earth leakage so that when the fault blows, it blows properly!

Obviously needs to be done with due regard for safety issues, and I'm probably going to take some flack for even suggesting it - but sometimes it is the only way to find the fault.

[AndyD]

For a few months now I have been experiencing random earth leakage problems - earth leakage switch tripping for no apparent reason. For a while it appeared to be both random trips and when plugging in a charger power brick for a laptop.

There's no reason a laptop power supply would cause earth leakage, they're usually Class II appliances and don't even have an earth connection.

I have now spent several thousand rands on replacing all sorts of things based on advice from sparkles, eg gate motor, pool pump, all day/night switches, plus I have had the garage/workshop rewired with a new DB and own earth leakage breaker because some of the problems occurred when the garage lights were switched on each day! Each of these faults was detected using a 'megger' (?).

Assuming the electrician removed the garage subDB from the RCD (earth leakage breaker) in the house when he fitted a new RCD in the subDB then this rules out the garage as being the problem. If the garage is still supplied via the main RCD in the house then without discrimination it's a lottery which one would trip fiirst to a fault in the garage.

I cannot find a sparky who can get me past this point.

This seems to be your problem. You need someone who's capable of localising and fixing this problem. You're going to have to get past the cheapest price mentality and find a good capable electrician and pay him his extortionate labour rate to find the problem.

I understand that the combined effect of power bricks and ups units (I have several ups units powering essential systems in the office) can create a background earth leakage level that makes the el breaker trip at very low additional el loads?

Firstly there's no such thing as background earth leakage. There's just earth leakage.... period. Earth leakage is usually measured in milliamps unless there's a lot of it and then it might be measured in amps.

Secondly class2 appliances (double insulated) such as cellphone and laptop chargers would have zero earth leakage. A UPS usually has a chassis with an earth so with the UPS it's possible to have a low insulation problem resulting in earth leakage. It is unlikely however and would easily be proved using a Mega tester.

I would appreciate some diagnostic advice as this is now driving me nuts!

My immediate diagnosis is that you need a decent electrician otherwise your prognosis is looking bleak.

RCD nuisance tripping is one of the more difficult problems to solve.
Start with sorting out the easy stuff and only then get complicated if necessary.
1 Ramp test both RCD devices.
2 IR test all circuits on the main DB and fix anything with an IR value of less than 2 MΩ.
3 Do same with Sub DB in garage.
4 Check both DB's for circuits with borrowed or crossed neutrals.

One thing you can do is keep a log of every time the RCD trips. Note the time of day, exactly what appliances are running and any other circuit breakers that trip at the same time.

Can you attach photos of the inside of the main and garage DB's?
Can you tell us whether the RCD resets first time after it trips?
The more info you can give the better.

fluorescent light fittings are a common problem when connected to an earth leakage units...when they ignite (start up) they cause tripping issues...

If fluorescent light have low IR readings then they're faulty. A fluorescent light should present no earth leakage even during ignition cycle.

My sparkies use the term "blow the fault clear." It involves taking the suspect circuits off earth leakage so that when the fault blows, it blows properly!

Not sure what 'blow the fault clear' means but the phrase is exciting in a very scary sort of way.

[BillH]

Thanks for your time to respond so comprehensively.

I found a USA forum where someone found that different laptop power bricks tripped his circuits from different points in his house. This is exactly what I have been experiencing. The forum responder said that this was common and that with many such units plugged in renders the earth leakage more sensitive. Seemed logical at the time - some transformers give quite a buzz if you touch the wall socket end when disconnecting?

I urgently need to find a good electrician who can fault-find in a scientific manner?

We have kept logs for a while but could not link the faults to any appliance switching on or off. We have three types of occurrence: entirely random, plugging in a charger or the garage light issue. The random could be ants or geckos but we cannot find where if this is the case. Maybe a frayed wire underground somewhere.

Thanks again!

[BillH]

I forgot to add that the earth leakage resets immediately.

[BillH]

Hi again,

In response to the make of earth leakage switch, they are not Heineman (my mistake) but are marked "CBi". Most of the other breakers on the boards are SAMITE, with one or two Heineman switches left over from the original DB when we built the house 30 years ago.

Is the CBi make OK?

[BillH]

Ok, today (Friday), had a random trip around 08:00 and the garage lights again tripped the house RCD and not the new one in the garage!

[murdock]

cbi...heineman...same company...the older earth elage units where the better ones...the new ones...seem to be a lot more "sensitive" to voltage fluctuations etc...or so i am told by the experts...but if the earth leakage is really old and has been causing endless tripping problem...it "could be a place to start...

having 2 earth leakage units in series is just unpracticle...the ony reason you fit one in an outbuilding...so that the person in the outbuilding doesnt have to keep going into the house to reset it...so you isolate the outbuilding from the main house..etc

the older type light fittings like the 8 ft double with the big ballast have caused many a headache for me in the past...especially in factories where we have multiple rows of lights...the newer 5 ft and electronic ballast units dont seem to affect the earth leakage unit as much...but then in saying that i dont connect light fittings to an earth leakage unit...and the fatories which i service...i remove the light circuits from the earth leakage...if they create an issue.

dave the sound of it is bad...but in theory only 15 amp plug sockets and a few other items as per sabs regulations are required to be on earth leakage...maybe they should try an insulation resistance tester "megger" before blowing them selves up... dont ever try that if you work near RBM or any of those big companies in richards bay...the DOL are like lice in that place

[Dave A]

maybe they should try an insulation resistance tester "megger" before blowing them selves up...

They do

And it's not that big a blow for crying out loud. Technically it isn't even a contravention of regs as long as the plugs are on earth leakage (and earthing, isolators etc. are all where they should be).

Certainly out of the question on heavy current stuff - but then in those situations nuisance earth leakage tripping doesn't normally come into play anyway.

I don't know how many times it's been the geyser after being left off for a few weeks that's been the culprit.
And stove plates at coastal holiday flats! Don't get me started on those...

[BillH]

Yes, it was replaced quite early in the process.