Sub board earth leakage trips when on at main DB

[Reginald]

I have a sub board in the studio, it keeps tripping (does not stay up) . When i turn the main boards breaker to the sub board Off in the house (main board) the sub board stay up. When i turn it back on in the house the sub board trips. All breakers at the sub board are off.  IS this a faulty earth leakage on the sub board?

[Marv]

Earth leakage breakers almost never go faulty. I'd guess that out of every couple of hundred earth leakage tripping faults one might be cause by a faulty earth leakage breaker. If there's a fault the earth leakage breaker will reset if the power to it is off then trip if the power is put back on, this is normal.

Earth leakage breakers are sensitive to faults on circuits they supply even if the circuit breaker for that circuit is switched off. This is because the earth leakage is monitoring both the live and the neutral wires and the circuit breaker only disconnects the live and the neutral remains connected.

If this is a new installation or if there have been changes to the installation recently then it's possibly a wiring fault within the installation.

If the fault started out of the blue then it's more likely an appliance that's faulty in which case unplug all appliances completely from all sockets and see if the fault goes away.

Some other things you can check are outside lights or connection boxes that might have leaked water or suffered an insect infestation. Check the geyser for water leaks or condensation where the wiring connects into it. Check for any signs of damp on the ceiling inside, maybe an internal light got wet.

[TaliaB]

On 2024/09/28 at 1:34 PM, Reginald said:

I have a sub board in the studio, it keeps tripping (does not stay up) . When i turn the main boards breaker to the sub board Off in the house (main board) the sub board stay up. When i turn it back on in the house the sub board trips. All breakers at the sub board are off.  IS this a faulty earth leakage on the sub board?

I agree the probability that you have a faulty RCD(earth leakage) is slim. It sounds like you have a neutral to earth fault. You have 2 types of leakage currents 1. Intentional leakage(all power supplies)and 2.Unintentional leakage current.(Appliances )All electronic devices with power supplies has  capacitors that leaks small amounts of currents (Class X and Class y capacitors are placed in EMI filter circuits on the front end of a power supply) Another culprit is the surge plugs at the sockets that protects equipment against surges they are normally reddish colour or green 3 prong plug tops. I would suggest if you have followed @Marvprocedure above without success then you need to call in an installation electrician as the next steps is dangerous if you are not familiar or able to do this safely. All neutrals needs to be disconnected from the neutral bar then all breakers needs to be switched on then connect each neutral one by one until the RCD trips then that is the faulty circuit. All connections on that circuit then needs to be traced out until the fault is located and eliminated. If your electrician has a ramp tester the RCD can be tested for correct threshold disconnection( normally 30 mA) in less than 300ms. 

[Clint]

On 2024/09/28 at 1:34 PM, Reginald said:

I have a sub board in the studio, it keeps tripping (does not stay up) . When i turn the main boards breaker to the sub board Off in the house (main board) the sub board stay up. When i turn it back on in the house the sub board trips. All breakers at the sub board are off.  IS this a faulty earth leakage on the sub board?

Just push the test button on the earth leakage ,this could give you an accurate account if it is faulty.

remember you cannot go from one EL to another one

My theory is when the power is on you have a neutral to earth wire short.

Try disconnecting all the neutral wires and connect one at a time to find the fault

For gods sake dont electricute yourself(I'm a registered electrician)

Good luck

[Scorp007]

1 hour ago, Clint said:

Just push the test button on the earth leakage ,this could give you an accurate account if it is faulty. 

 

I'm not so sure. The test button will only indicate if you exceed the threshold it would trip. If it doesn't trip yes then it indicates it is outside of spec. It still does not indicate if it perhaps trips at a level lower than the common 30mA.

For a correct value one needs to test as per the reply from @TaliaBTaliaB earlier. 

[HendrikBigChief]

13 hours ago, Clint said:

remember you cannot go from one EL to another one

 

What does that mean?

[Scorp007]

1 minute ago, HendrikBigChief said:

What does that mean?

I can just assume it is meant as in series. Like a main E/L on a DB that is then wired to a sub E/L. 

[Clint]

10 hours ago, Scorp007 said:

I can just assume it is meant as in series. Like a main E/L on a DB that is then wired to a sub E/L. 

Correct

[Clint]

22 hours ago, Scorp007 said:

I'm not so sure. The test button will only indicate if you exceed the threshold it would trip. If it doesn't trip yes then it indicates it is outside of spec. It still does not indicate if it perhaps trips at a level lower than the common 30mA.

For a correct value one needs to test as per the reply from @TaliaBTaliaB earlier. 

Correct I use a E/L tester at every job I do.

I also find that all the E/L I test the test button has always indicated if the E/L is functioning correctly.

Maybe one day I,ll find one that does not.

[Marv]

To find an earth leakage fault I'd use a ramp tester on the E/L breaker first to test it but it's extremely rare to find one that fails. Occasionally there will be one that's a bit on the slow side on the 5x test at 0° or 180° but usually they all usually pass after they've been operated a few times.

If it's an immediate trip problem I'd isolate power then split all the RCD final circuit neutrals and test each circuit individually. This test would be a 250v IR test but as mentioned by Clint you could also reconnect each circuit one by one and live test until you find the culprit.

If it's an occasional tripping fault I'd do a live global leakage test at the earth leakage breaker and live leakage tests of each circuit using an earth leakage miliamp clamp meter by clamping the live and neutral simultaneously to give an indication of total leakage both down the CPC and also through parallel earth paths. The beauty of using a clamp meter and doing it as a live test is you're seeing exactly what the earth leakage breaker is seeing including functional leakage such as EMI and common mode suppressors etc as well as fault leakage due to low IR values. Doing an old fashioned megger or IR test at 250v will give you a good idea of the earth leakage due to faults but won't accurately reflect functional leakage values.

Bottom line for a home owner is it's cheaper and easier to call an electrician if you can't localise the problem by unplugging appliances and visual inspection. Unfortunately finding these types of faults isn't possible with a R50.00 multimeter from Builders Warehouse, an RCD ramp tester is going to cost a minimum of R5k for the cheapest and maybe R15k for a decent one, an earth leakage clamp meter is about R15k for a decent one and even a megger tester is R5-6k for a basic analogue version. Just call a decent spark in and don't moan when he charges you 800 bucks an hour if he's arriving at the job with 30 or 40 grand of test equipment.