Another tripping RCCB

[CallumWK]

I have followed @carlyai thread with interest, as I have a similar issue, in my maid's quarters.

The maid's quarters is about 30 meters from the house and fed by an underground cable coming from the main house, and on a circuit that has a 63A RCCB.

 

MQ has never been occupied, and for the last few years the RCCB in the house tripped maybe once every few months, which I attributed to the pool pumps being on the same circuit. But when I closed the RCCB again, all would be fine.

About a month ago it tripped during heavy rain, and then I found out that the issue was in the MQ, because I couldn't close it until I opened the MCB to the MQ. I left it like that for more than a week, but then the problem still existed, so I started checking.

 

In the MQ there is a 2 pole 40A MCB (ABB S202M) and 5 single MCB's. Unfortunately, the breakers are not marked which circuit they cover.

Everything is switched off, I switch 2 pole MCB on, no problem. I can switch on MCB 1 and 3 without the RCCB in the house tripping.

Whenever I switch on MCB 2 - 4 or 5 the RCCB trips immediately, and can not be closed unless I open MCB 2 - 4 and 5. As said nothing is active in the MQ, nothing plugged in the sockets either.

 

I already removed all neutrals from the neutral bar, as suggested in the other thread, but that doesn't make a difference.

 

So now I would like to try another RCCB, but I'm not gonna part with 2500 baht for an ABB RCCB, just for testing purposes, so any suggestion on a cheaper/reliable brand are welcome.

 

I should add, the house and MQ have earthed electrics and are 12 years in use.

 

 

 

[carlyai]

While looking for my garage wiring circuit I found this about about a home built RCD test device.

The web site is This is Prathumthani, I think.

The information may be in the pinned threads at the start of the Electrical Forum as is from Crossy I think.

[Crossy]

1 hour ago, carlyai said:

While looking for my garage wiring circuit I found this about about a home built RCD test device.

The web site is This is Prathumthani, I think.

The information may be in the pinned threads at the start of the Electrical Forum as is from Crossy I think.

 

That's probably the only currently accessible copy of that website in the known universe!

 

The WaybackMachine is down after a cyber-attack although they say that the data is safe and they will be back "soon".

[Crossy]

15 hours ago, CallumWK said:

Whenever I switch on MCB 2 - 4 or 5 the RCCB trips immediately, and can not be closed unless I open MCB 2 - 4 and 5. As said nothing is active in the MQ, nothing plugged in the sockets either.

 

Time to find out what these MCBs control and investigate, I'll bet the damp has got in or the local wildlife has had a nibble.

 

If not already done, pop off all your outlets and light switches to get any damp or creatures out. Madam's hair-dryer is a useful tool!

 

Since you can get two MCBs active, check what they control (and record) so you at least have an idea what not to look at.

[CallumWK]

This morning I decided to open all the MCB's on the same circuit as the RCCB in the main house, then went to the MQ and closed all MCB's there.

Following that I opened the MCB to the MQ and the RCCB didn't trip. Next I closed all the MCB's on the circuit, and it still didn't trip.

Now I went to the MQ and opened all lights - fans and the outside floodlights, still no tripping.

At that moment it started raining and the brown outs started, so had to stop testing.

Will update tomorrow.

 

[CallumWK]

So after the power was restored t 10pm yesterday, I started testing again today. There had been heavy rains all day yesterday, so surely plenty of water in the ground, and moist everywhere.

Closed all MCB's in the MQ, then closed the MCB feeding the MQ in the main house board. No RCCB tripping.

Opened all lights and everything else in the MQ, till no tripping. Started some heavy consumers on the same circuit in the main house, like pool pump with chlorinator and deep well pump, still no tripping.

Lesson learned, I have to start a thread on this forum earlier if I want something fixed mysteriously.

[CallumWK]

Tell me if I have a problem.

As explained, RCCB doesn't trip anymore, but I now started to test the 5 individual MCB's in the consumer unit.

 

MCB 1 - I can't find power anywhere

MCB 2 - every light switch - power socket - outside lights has power.

MCB 3 - I can't find power anywhere

MCB 4 - every light switch - power socket - outside lights has power.

MCB 5 - every light switch - power socket - outside lights has power.

 

Maybe MCB 1 and 3 individually power the water heater and cooking hood, not easy to check, but sure the other 3 MCB's should not each power everything.

Where should I start?

[Crossy]

3 hours ago, CallumWK said:

Tell me if I have a problem.

As explained, RCCB doesn't trip anymore, but I now started to test the 5 individual MCB's in the consumer unit.

 

MCB 1 - I can't find power anywhere

MCB 2 - every light switch - power socket - outside lights has power.

MCB 3 - I can't find power anywhere

MCB 4 - every light switch - power socket - outside lights has power.

MCB 5 - every light switch - power socket - outside lights has power.

 

Maybe MCB 1 and 3 individually power the water heater and cooking hood, not easy to check, but sure the other 3 MCB's should not each power everything.

Where should I start?

 

I'd start with a beer!!!

 

[CallumWK]

I have started removing wires from the MCB's, as 2-4 and 5 had each 2 or 3 wires attached, and now are trying to find out where each wire leads to by providing power individually.

 

I found one wire that comes out of the wall, which has 230V on it when MCB 2 or 4 are closed. That wire was attached to MCB 5. I have for the time being that one cut off

[Crossy]

Please be careful!!!

 

You should really be doing this with your continuity tester (battery and bulb, or your meter) with the juice off!

 

[CallumWK]

There is only 1 red wire that get current from one of the appliances, and that one is insulated already, all the others feed something.

I intend to remove them all and then use just 1 MCB, and connect 1 wire at the time, then check which light or socket works, and mark the wire.

I have a multimeter.

I don't really understand the principle of a borrowed neutral, because after all they all connect to the same neutral bar.

To check on borrowed neutral I assume that only can be done above the ceiling in the junction boxes. Is that correct, because if so that will require an electrician

[MangoKorat]

Just a thought from a non electrician - although I agree with Crossy that your problem is probably due to moisture............. I've known leakage on Thai sockets and light switches.  Some seem to be very poorly insulated and the insulation that does exist seems to break down over time. I discovered this after getting a 'tingle' from a light switch - I went round checking all sockets and switches with a meter and a small voltage was present on quite a few - on the plastic!!! The one that gave me a 'tingle' was registering over 100 volts!!!

 

Also, because many Thai houses don't have a separate lighting circuit, when testing for moisture, you may also need to check the light switches/fittings.

 

It took me a while to work out how the lighting in my house is wired - a simple live taken from a socket in the room 😁.  The lights seem to have their own neutral though - so that's alright then 😁.

[sometimewoodworker]

4 hours ago, CallumWK said:

I don't really understand the principle of a borrowed neutral

You and a lot of Thai “electricians”

 

the principle of an RCBO is that the same current must flow through the line and neutral conductors 

 

many Thai electricians will disregard having a single pair of wires for a single circuit that is supposed to be protected by an RCBO and use any neutral or borrowing it from a different circuit. This means that the RCBO will either trip instantaneously or trip at random intervals.

 

Finding and eliminating borrowed neutrals is a time consuming job and took a genuine election almost a complete day as our house had been originally wired up by a typical electrical fitter who had any neutral around. 

[carlyai]

When the Sparky wired my house I counted the red wires and black wires (old power cable colour code). All added up but 2 less blacks as had 2 three phase heaters.