Home power intermittently tripping

[DPG]

Did you say you had had your RCD tested?

 

[devion]

Update - Been more than 10hrs with no trips, I conclude it is the fridge defrost heater causing the random trips. Ytd when I terminated one of the wires to the heater unit, I actually worsen the condition & experienced more frequent trips of 3-4hrs interval vs previous 12hrs. Read the manual of my fridge & it did state auto defrost every 4 hrs.
After disconnecting the defrost connection from the control board, the entire defrost heater is now terminated from the controls & power.
Thanks all to have provided feedbacks for my past 1 week plus ordeal.
Random power trips in middle of night w/o additional loads, trips in specific intervals of time, good lesson learnt here of what is the likely cause for such predictable patterns on trips. The one thing that confuses me was my bedroom MCB tripped occasionally & made me run a wild goose chase to start isolating devices from my bedroom. Funny that kitchen MCB did not trip where my fridge was.

 

[DPG]

I'm still intrigued by that bedroom MCB tripping.

 

[devion]

I'm still intrigued by that bedroom MCB tripping.

I spoke too soon, tripped again at the 11th hour. Its frustrating now. Guess will have to engage professional service to investigate, probably wait after my new fridge arrives in 4 days time. Sigh...
One electrical company provided me standard package for basic checks, troubleshoot live out-going, circuit breaker trip/function test, short circuit test & water heater connections, additional charges if need to further isolate the root cause.

 

[DPG]

Yeah definitely need to get some testing done. Keep us posted.

 

[devion]

Update - fridge was replaced & past 2 days no more random trips. Fridge was the cause but maybe not e defrost heater unit since I disconnected it from main circuit board, or maybe its still connected somewhere? Should have terminate e other end of the heater to confirm. Another interesting finding was even when fridge power is shutoff, it can still trip with the power cable still plugged in.
Suspect some residual current was still leaking after just turning off the fridge during e trip occurrence.
Lastly as in why my other MCB to bedroom was occasionally tripping, no idea on this. However this MCB is just beside the MCB connected to my kitchen where fridge was. Whether due to some kind of interference or something, it trips it. This one really blew me to a wild goose chase & doubting the fridge to be the culprit in the beginning stages of the frequent trips.

 

[Mike Johnson]

You need to unplug the fridge so it is totally isolated from your power, switching it off does not isolate it.

 

[DPG]

And did the RCD get tested?

 

[devion]

Wanted to update since my last one. After 3 days of no trips, it tripped again which concluded it was not the fridge. I continued to isolate individual devices in my room that had that occasional MCB trip during the frequent RCD trips, until one of my PC 750W power supply encountered an issue that my PC was able to power up & unable to boot up. After removing this PC out, no more trips observed for more than a week. Indeed it was one of my devices in the room causing this intermittent RCD trips.
Googling about earth leakage current causing trips, understood that it is the accumulative of leakage current of each devices that will cause the RCD to trip if it exceeds the limit. During my meddling with the fridge defrost heater, it probably caused more leakage current in my home circuit which then incur more trips & made me to suspect to be the fridge.
The lesson learnt here is that when isolating each device, need to unplug the cable from the power socket, the rogue PC that had been shutdown during times of trips made me not to suspect it to be the cause.
I was wrong about this.
A quicker method to check for high earth leakage current from each device is to use a leakage current meter & probe it with the live n
neutral wires of the device, & if the cable has an earth together with the live and neutral cables, need to exclude that from the measurement.
Saved some money of not calling an electrician to check. The PC power supply was RMA to the vendor as it is still under warranty.

 

[DPG]

I hate to bang on, but an RCD test when i suggested it would have helped .

 

[Mike Johnson]

Even unplugging every appliance and plugging them back in one at a time may have also helped, just switching them off never does anything, except fool you.

 

[Electro-tech]

I hate to bang on, but an RCD test when i suggested it would have helped .

The obvious solution ! After all the tripping over that time the device may have become too sensitive & not latching properly

 

[devion]

RCD test, can elaborate more what is this? Can it done by my own or require license electrician?
Unfortunately, today my main RCCB tripped again, after 5 days!!! This time I managed to use my recent purchased GFCI power socket & then I plug my 2nd PC to this. Within minutes, the GFCI tripped w/o my mains tripping!!!
This GFCI socket actually tripped 2x when I turned on my 2nd PC connected to it, so I replace the power supply with a spare. Now am monitoring.
This is indeed very hard to determine with the longer intervals of a trip event but am subtly confident that am nearing a fix.

I did contact electricians & explained my issue, at least 2 of them stated that they cannot guarantee a fix but they can help narrow down the cause/s. They mentioned about mega ohm the circuit to check which I believed it is measuring the amount of leakage current in each circuit in my household.
Hopefully today's incident with the GFCI socket tripping on my 2nd PC is inferring the issue to be my PC, power supply or other components, this I might not know, at least I had the power supply replaced & monitor.
Very frustrating as it is very random & now becoming more sporadic & less frequent.
Am also hoping that the main RCCB is still fine, in case it gets much more sensitive to earth leakage after this many tripping...50x at least for now. I believed my RCCB is rated at 30mA, I googled the various RCCBs available out there, saw some which is rated at 100mA, not sure whether this is safe for household usage, which I thought can handle more higher leakage current appliances.

 

[DPG]

RCD test, can elaborate more what is this? Can it done by my own or require license electrician?
Unfortunately, today my main RCCB tripped again, after 5 days!!! This time I managed to use my recent purchased GFCI power socket & then I plug my 2nd PC to this. Within minutes, the GFCI tripped w/o my mains tripping!!!
This GFCI socket actually tripped 2x when I turned on my 2nd PC connected to it, so I replace the power supply with a spare. Now am monitoring.
This is indeed very hard to determine with the longer intervals of a trip event but am subtly confident that am nearing a fix.

I did contact electricians & explained my issue, at least 2 of them stated that they cannot guarantee a fix but they can help narrow down the cause/s. They mentioned about mega ohm the circuit to check which I believed it is measuring the amount of leakage current in each circuit in my household.
Hopefully today's incident with the GFCI socket tripping on my 2nd PC is inferring the issue to be my PC, power supply or other components, this I might not know, at least I had the power supply replaced & monitor.
Very frustrating as it is very random & now becoming more sporadic & less frequent.
Am also hoping that the main RCCB is still fine, in case it gets much more sensitive to earth leakage after this many tripping...50x at least for now.

A ramp test will determine at what amount of leakage the RCD trips at. It will need a proper tester to do this (either a dedicated RCD tester or a multi function tester)

 

[devion]

Likely my final update. It finally got down to the PC PSU power cord causing the trips, but it was really weird in how this came about. I was using my PC with a replaced PSU connected to a GFCI power plug for few days w/o issues. I then head off to a week vacation & off mains power to this PC.
When I returned from my vacation & powered on this PC, my RCCB tripped immediately. I was dumbfolded. I was able to repeat this again & so its now very consistent that my PC caused this trip, but a week ago I was using this w/o issue.
When I unplugged the PSU power cord from it, I did noticed the end of the cord to have a tiny bit of liquid on it....tried to smell it but nothing.
I found another power cord & plugged this into this PC & there was no trip. Next I simply plug the problem power cord w/o load to a power socket, the moment I turn on the power, my RCCB tripped.
I tried to use a multimeter to measure the 3 pins of this cord but I was not able to read any ohms between them.
Dunno how this could have occurred, especially when this power cord was used fine a week ago & after powering off & a week later, this same cord had a catastrophic failure. How puzzling is this....some degradation of the cables within this cord?
What was that tiny bit of liquid found at the ends where it connects to the PC PSU?
I will try to cut open the cable to check for internal cabling issues. Maybe around the ends, might have some cable kinks that resulted in internal damages.

 

[Lucien Nunes]

Thanks for the update!

Detachable appliance power cords vary in quality from excellent to nightmare, often with few visible differences to tell them apart as the bad ones usually have counterfeit approvals moulded in. They are often bundled with the appliance at a late stage by the vendor, and may not be of a quality that the OEM of the goods would approve. I have seen high-end professional media equipment costing $30k bundled with cords that did not meet the applicable regulations, because the global distribution warehouse purchased them separately to match the plug requirement of the destination country.

Problems found in defective and counterfeit cordsets include undersize conductors, aluminium instead of copper, out-of-spec plug pins, unapproved and non-sand-filled fuses, female contacts that are not correctly touchproof, reverse polarity, shoddy spot-welding and complete disconnects at the terminations, etc. etc. On this forum, we heard about a cord that was giving people shocks where the black plastic moulding of the connector body was partially conductive, presumably through contaminated plastic feedstock containing carbon being used in the moulding line. We have also seen a plug where the spot-weld tags were less than 1mm below the top surface of the plug and the slightest damage would allow them to punch through and be exposed.

Another cable manufacturing error that we saw causing intermittent faults was a mechanical splice, intended to draw a new length of conductor into the extruder, that had been allowed to run through and gotten into the finished cable, which cut through the adjacent core's insulation. Presumably they didn't even do a water bath test on the insulated core before making up the cable. I can imagine some constructional defect like this being responsible for your problems. It will be interesting if you are able to dissect it and find something definite.