RCD random trips

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surfisup1000

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#191412 3-Feb-2016 16:30

The RCD on our house pops at seemingly random times.

Just came back from holiday to find our power off due to a RCD trip-- luckily it was just the day before as the freezer was still cold.

But, if we go on a longer holiday it could be a disaster, with our freezer and fridge going off.

Is it possible to even diagnose this for a reasonable price?

We did have an earlier issue where the ice defrost heat element in our fridge was causing constant RCD tripping --- but that was fixed early 2015 .

This seems completely random and reasonably infrequent (5-10 times a year maybe).

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#1484557 3-Feb-2016 16:36

RCD trips can be a nightmare to trace, been there done that, couple of random trips a year, and then bang it went totally troppo and tripped all the time.

Eventually at the end of a long night of circuit tracing and testing, we concluded the easiest option was to replace the RCD module,

Subsequent testing of the module on a test bench confirmed it was in fact faulty...

If you are worried, get your sparky to replace it...

gregmcc

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#1484568 3-Feb-2016 16:49

And it's quite possible you have a mouse that is chewing on the wiring somewhere, big problem it could be one of many things in many places.

surfisup1000

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#1484611 3-Feb-2016 17:40

gregmcc:

And it's quite possible you have a mouse that is chewing on the wiring somewhere, big problem it could be one of many things in many places.

You mean we get the trip when the mice chew on the wire?

Anything is possible.

I am thinking about getting the RCD replaced as per the previous poster. But, it is like hunting for a needle in a haystack.

I think the person who invented the rcd should have built in a method to spot faults. At the very least, say which circuit caused the trip. If that is even possible.

gregmcc

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#1484639 3-Feb-2016 18:03

surfisup1000:

gregmcc:

And it's quite possible you have a mouse that is chewing on the wiring somewhere, big problem it could be one of many things in many places.

You mean we get the trip when the mice chew on the wire?

Anything is possible.

RCD can't tell the difference between a mouse and a person

I am thinking about getting the RCD replaced as per the previous poster. But, it is like hunting for a needle in a haystack.

I think the person who invented the rcd should have built in a method to spot faults. At the very least, say which circuit caused the trip. If that is even possible.

if the tripping is happening on a more frequent basis, try leaving some of the circuits off to see if the ones left on still trip the RCD, remember the RCD is there to save your life when there is an fault, you can get your electrician to replace it, more than likely the fault isn't with the RCD, it's somewhere else and the RCD is doing it's job

richms

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#1484725 3-Feb-2016 19:16

Get it split out with RCBOs on each circuit instead of a single RCD for heaps of them. There is a limit of 3 per RCD now to stop cheap-ass sparkies sticking the entire house on one.

At least get the fridge and freezer stuck on their own RCBO so they dont trip out with everything else.

Also replace any powerstrips with surge protection in them. Old ones had capacitors between live and earth, and neutral and earth which can cause more current to flow to earth making trips more likely.

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surfisup1000

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#1485044 4-Feb-2016 09:51

richms:

Get it split out with RCBOs on each circuit instead of a single RCD for heaps of them. There is a limit of 3 per RCD now to stop cheap-ass sparkies sticking the entire house on one.

At least get the fridge and freezer stuck on their own RCBO so they dont trip out with everything else.

Also replace any powerstrips with surge protection in them. Old ones had capacitors between live and earth, and neutral and earth which can cause more current to flow to earth making trips more likely.

OK, I'll try the power strip thing as a start.

It basically sounds like I am largely stuck with this problem though, between the mice, the powerstrips, and the cheapo sparkies :) We have 2 RCD's, but, a ton of stuff on each. Big house big problems.

I have a feeling it is the fridge doing the tripping, as that was the culprit last time . F&P so wouldn't be surprised.

But, it is basically impossible to diagnose this from what I can tell - 1 trip each month or so cannot be isolated. Easy if it tripped constantly.

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mclean

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#1485069 4-Feb-2016 10:47

surfisup1000:

It basically sounds like I am largely stuck with this problem though, between the mice, the powerstrips, and the cheapo sparkies :) We have 2 RCD's, but, a ton of stuff on each. Big house big problems.

I have a feeling it is the fridge doing the tripping, as that was the culprit last time . F&P so wouldn't be surprised.

But, it is basically impossible to diagnose this from what I can tell - 1 trip each month or so cannot be isolated. Easy if it tripped constantly.

Don't accept that you're stuck with the problem.

As a first step, get a sparky to do an insulation test. Then measure the earth leakage current - if there's a measurable leakage up near the trip current then it's relatively easy to track down the fault. Then replace the RCD - otherwise you may be chasing rainbows.

If that doesn't work then things get harder. Heating elements and motors are common culprits, especially HWC/oven elements that get used infrequently. Or moisture getting on to a control board or something similar. Or an insulation fault.

Until you get it fixed, when go on holiday you turn off all your cookers/water heaters and unplug everything from the wall except the freezer.

10 trips per year is a fault that you need to fix.

surfisup1000

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#1485072 4-Feb-2016 10:52

mclean:

Don't accept that you're stuck with the problem.

As a first step, get a sparky to do an insulation test. Then measure the earth leakage current - if there's a measurable leakage up near the trip current then it's relatively easy to track down the fault. Then replace the RCD - otherwise you may be chasing rainbows.

If that doesn't work then things get harder. Heating elements and motors are common culprits, especially HWC/oven elements that get used infrequently. Or moisture getting on to a control board or something similar. Or an insulation fault.

Until you get it fixed, when go on holiday you turn off all your cookers/water heaters and unplug everything from the wall except the freezer.

10 trips per year is a fault that you need to fix.

Is it possible to detect a fault while it is not currently causing a trip?

I think I'll take your advice first, get in a sparky to check it out. Then, go from there.

mclean

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#1485078 4-Feb-2016 11:08

surfisup1000: Is it possible to detect a fault while it is not currently causing a trip?

Yes. A leakage current of say 25mA won't trip a 30mA trip RCD, but normal variations in the leakage current on top of that could cause an intermittent trip. A sparky can measure the leakage current. If there's something unusual there then you're in luck.

Fred99

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#1485093 4-Feb-2016 11:22

HWC and ovens aren't normally on RCD protected circuits.

I'd be suspecting the fridge (again). If they replaced the defrost element, then they probably replaced it with same part, if there's an issue with that part, then...

Having multiple RCDs on different circuits doesn't necessarily solve a problem here (if it's the fridge) except making preliminary diagnosis by process of elimination a easier. If you go away for a few weeks and the RCD trips, then if you have to reset clocks etc on a few things it is a minor inconvenience - not so if you come back to find your fridge/freezer off and the house smelling like it's full of rotting corpses. When we go away for more than a day or two, I turn off everything anyway - in a household with the usual plethora of wall-warted and electronically switched devices left on standby, it's not worth the risk. The fridge is the only thing left on - mission critical you could say.

Note that the CGA includes compensation for consequential damages. If your fridge stopped and the contents rotted due to a fault determined to be because of some deficiency / failure from the supplier or repairer, then the fridge would probably be a total loss as well as the contents, and there'd probably also be costs for professional cleaning of the house.

BTR

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#1485206 4-Feb-2016 14:02

Is there any appliance on that circuit that isn't used often? Get a sparky to check all of the wiring to each sockets on the circuit. It could be as simple as a lose connection that a truck driving pasts causes a vibration that causes it to trip.

Also stupid question but its the RCD and not a MCB?

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surfisup1000

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#1534506 17-Apr-2016 18:21

OK, some good luck, if you can call it that. It is our house alarm.

The rcd tripped again recently, then again last night. After that, it was tripping every time we switched on the RCD.

So, we have about 10 trip switches on the one RCD circuit. 5 labelled lights, 5 labelled power.

When all 10 are "On", the RCD trips right away. Process of elimination, found that when one of the 'light' trips is off, the RCD doesn't pop. And, the alarm is wired into this particular lighting circuit. So, we switched off the alarm , and presto , no more trips. It was lucky because whatever fault is in the alarm worsened over time to the point where it would cause permanent RCD tripping.

The one thing I find a bit weird/troubling though, is that if we switch off all 10 trip switches and then turn on just the alarm trip switch, the RCD does not pop.

The RCD only pops when the alarm/light trip, and a few other trip switches are on.

Which makes me think we might have current leaks on the other circuits. And the RCD only trips when the cumulative leakage across all circuits exceeds the RCD threshold .

Anyway, the good news for now is that we can get an alarm technician in to fix this. We had issues with the transformer in the past, making a significant humming noise. Didn't think that was normal. The alarm is connect to the copper phone line, which is inactive too now that we have ufb. Might address that issue too.

Aredwood

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#1534649 17-Apr-2016 23:31

There are other things in your house that have current leaks. Some which cannot be avoided. Such as capacitive coupling in your wiring. And the interference filters that are built into every switchmode power supply. (the filter circuits contain small capacitors wired between the phase / neutral and earth).

See if you can get a dedicated RCD installed just for the circuit that supplies the fridge. If you cannot get all of the circuits split out to individual RCDs. As 10 circuits on that RCD means average leakage current of only 3mA per circuit. In reality lower as RCD will trip at less than 30mA.

Supposedly the electrical rules will soon require the use of Arc Fault circuit breakers. Hopefully they will also allow Arc Fault breakers to be used instead of RCDs on some circuits. As Arc Fault breakers provide better protection against electrical fires starting. And no problems with nuisance tripping due to small amounts of earth leakage.

linw

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#1534681 18-Apr-2016 08:28

Had to look it up but Arc Fault Breakers sound like a very good idea. Thanks for the education!

surfisup1000

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#1534716 18-Apr-2016 10:18

Aredwood:

There are other things in your house that have current leaks. Some which cannot be avoided. Such as capacitive coupling in your wiring. And the interference filters that are built into every switchmode power supply. (the filter circuits contain small capacitors wired between the phase / neutral and earth).

See if you can get a dedicated RCD installed just for the circuit that supplies the fridge. If you cannot get all of the circuits split out to individual RCDs. As 10 circuits on that RCD means average leakage current of only 3mA per circuit. In reality lower as RCD will trip at less than 30mA.

Supposedly the electrical rules will soon require the use of Arc Fault circuit breakers. Hopefully they will also allow Arc Fault breakers to be used instead of RCDs on some circuits. As Arc Fault breakers provide better protection against electrical fires starting. And no problems with nuisance tripping due to small amounts of earth leakage.

Thanks for the reply, you seem to know what you are talking about.

So, I have a lot of ac adapters around the house. I'm guessing, probably somewhere between 30-50 plugged in around the place.

As for the fridge, yes, I understand why. Our fridge was causing one of our trips last year when the internal defrosting element failed (for the second time). But, hard to figure out because it only happens randomly at first. An electrician couldn't have figured it out as it only happened 'sometimes' when the heating element came on. Although, I guess fridges may be the primary reason for trips so they might have zeroed in right away.

I like the idea of these arc breakers. RCD trips have been a nightmare for us.

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