Tripping RCD (earth leakage detector)

[bennylaird]

There have been very noisy rodents (rats or possum) active in the roof and now the RCD keeps tripping. I will get a sparkie in but just trying to think things through.

I suspect some chewing of wire insulation first up but cannot get into all the cavities to check this out. Also that funny wet stuff has been falling a lot and maybe some dampness has caused the problem.

I'm just trying to work out how the sparkie would go about this. Use an earth leagage tester on the fused circuit that seems to be the culprit then keep half splitting to locate the problem?

Biggest problem is I'm working all weekend and cant look into it leaving the family to work things out but the other problem is the wood for the fire is stored behind electically operated rolladoors on the offending cct. Hence no wood to light the fire.

Think my best bet is to find some time and get the sparkie out and hope someone else can be at home to let him in etc.

Sometimes silly stuff like this can really ruin your whole weekend.

[Ashore]

Incase its something inside benny UNPLUG ( don't just turn it off )everything on that circuit, if it still trips (and I take it it is only one circuit) then you need a sparkie, if it doesn't trip plug one thing in at a time and turn it on until the earth leakage trips again, from what you have said though I think it could be the wiring but at least you will have eliminated anything pluged into the circuit

Rgds

[bennylaird]

Ta Mate, been going down that path with no luck so far so handing it off to a sparkie is the best move. Just wondering how he would trace it. Cheers.

[Bodgy]

Benny

I understand that the two worst offenders causing the leakage are the fridge and the steam iron. The iron should be easy to isolate, but the fridge seems to be more random.

If it does turn out to be ferals in the roof space, good luck finding the hole. For what its worth, I had a puppy who gnawed on a power lead to the pool pump. I coated the lead with a mixture of cayenne pepper, Susie's favourite sauce (paint stripping chilli type from the Windies) sump oil and citronella. The dog never went near it again.

[emptybucketman]

The electrician should conduct an insulation resistance test on the entire installation using a megger (IR tester) and then on each cct if required.

[Cliff Rogers]

As I read it, Benny already knows which circuit is causing the problem & the fact that the RCD trips when that circuit is turned on already makes it perfectly clear that there is an earth leakage on that circuit so a megger is not going to tell them any more that what they already know.

What the sparky will have to do is try & work out the route that circuit runs.
Finding all the sockets on that circuit is simply a matter of leaving just that circuit isolated & checking to see what points don't have power.

Then pick a GPO part way along the circuit & pull it off the wall & break the circuit at that point & try it.
Then, by using the half spit rule, work toward or away from that point til he finds the section of circuit that has the fault in it.

Finding it shouldn't take too long, then it is just a matter of pulling a new piece of cable through using the old piece as a draw wire.

[NCArcher]

That's pretty much it Cliff.
If it turned out to be rodent eaten i would be setting some baits and/or blocking up any holes. If they chewed it once they'll do it again.

[DavidG]

If the problem is rodents.

The fact that the RCD is tripping probably means that the rodent that did the biting wont do it again. It is the leakage.

Fried rodent any one.

[NCArcher]

Not necessarily. I've seen lots of cables chewed back to bare copper with no sign of the culprit. (Seen a few fried ones as well) Can be a bit iffy when you find bare copper, usually the hard way.

They have to chew through Active and Neutral/Earth at the same time and take a good bite to get zapped. And the RCD probably saved him so he could run away to chew another day.

[spartan]

Rodent trips of RCD in winter a very common. A megger is an obvious tool to start fault finding. But assuming that you can't easily meet up with a qualified electrician there are some simple, safe, and effective things you can do to narrow the problem down.

After checking the obvious - water around kettle/jug, condensation on the top of out door appliances, Its less common that rodents will chew through wires that have 240V or higher flowing through them - they usually stop before they get that deep. They are much more likely to chew through your phone, computer, and tv cables though...

What you often find is that they are stepping on exposed contacts in electical devices - particular reverse cycle air cons in this weather. (Its cold in Brisbane this time of year!). They also pee everywhere and that causes problems too.

Another important point to note is that there is residual earth leakage present at all times. Some device leak more often than not. Some electrical components that have deteriated will progressly leak more until the 30MA barrier has been reached.

Given your availability problems consider purchasing from Jaycar a powerpoint tester with an integrated earth leakage tester in. They cost about $20.

Plug it in and test at 10MA and then 15MA - if the RCD trips that will indicate that you have a residual earth leakage problem - of somewhere just below 30MA. It then trips when devices are under load - motors start etc.

[emptybucketman]

If you've disconnected all the portable appliances and the RCD is still tripping then it is time to call in the electrican. It is best practice to use the megger all the way down to isolating the fault in the section of the cable rather than relying on the RCD trip. Also the standing leakage on the circuits protected by the RCD can be determined.

In any event, ensure that an IR test is conducted on the entire installation after the repair.

[rat52]

I recall a problem on a building site where the rcd was tripping out at random times.

It turned out to be the coke machine. There was a evap tray in the bottom with a faulty wire and whenever the tray had water in it it would trip.

[thatirwinfella]

I recall a problem on a building site where the rcd was tripping out at random times.

It turned out to be the coke machine. There was a evap tray in the bottom with a faulty wire and whenever the tray had water in it it would trip.

i had a similar thing happen at work, where a heater element in the evap tray had burnt out.

we tested the resistance, and it was a half ohm across active and neutral.

it was tripping the 200A breaker of the main panel before it was tripping the 16A breaker on the sub board.

contractors had done the canteen, and had stuffed up the breakers...

[bennylaird]

Gudday Guys Thanks for all the help and advice. Problem is now fixed.

I knew which circiut was the problem and went about the half split rule to isolate it. The run went through the lounge, a bedroom then through a brick wall to the double garage. Isoloted it there and all was well, next half split was garage, automatic doors then into the storeroom off the garage. Here it left the house to head off to the shed. Isolted it here and all was well again.

Out to the shed and a connection from there went underground and about 30 metres to the septic tank overflow tank. Isolted it in the shed and all was well.

Looks like the submerged pump in the overflow has developed a leak and that must be the problem.

As usual the half split rule did work but I started from the wrong end. Didnt realise where the run went till I chased it down. Silly thing is after all that run I'm only 20 metres from the power box where I started after a run of about 100 metres.

As i was selling wine for most of the weekend I didn't have time to get a sparkie in after all. Just managed to keep the rest of the family annoyed by dropping the power off whenever they were enjoying tv. Now to go and stoke up the fire now I have wood again.

Up for the cost of a new pump I guess. But at least we can access the fire wood now and warm up.

[bennylaird]

Spartan, you reminded me of Malaysia. Not rodent pee but whatever comes from coackroaches. What ever is in it is bad, totally corrodes everything it touches. We used to get it inside most of our equipment. That and fried geckos.