Random RCBO Trip...What Next?

[carlyai]

Trying to isolate which electrical cct. is causing random trips of a RCBO. 

With all the feed breakers (to greenhouse pumps, aquaphonics pumps and air pumps, pool pump and chlorinator disconnected), the main breaker in the garage CU still trips intermittantly.

I blew out all the red ants etc from the garage CU and thought the problem was fixed, but RCBO still tripping, but not nearly as much. This only started this wet season.

I don't really need the breaker to be an RCBO but installed it before the underground feed to the shed as the underground feed is Al cable (which I now know is a no no) but 7 odd years ago the local electrician said OK.

The circuit: from the 3 phase mains PEA supply to a CU on the 2m block fence, then splits underground to the house CU via 3 single phase stabalisers, then a phase to the RCBO on the fence, then underground to the shed CU.

So to my questions:

1. Can the main shed CU breaker go leaky and should I change it?

2. Should I replace the wall RCBO with a normal MCB?

I don't think the Al cable feed to the shed is a problem, at the moment, even though the conduit probably has water in it, because the Al cable is double insulated and thicker than the recommended underground cable.

This cable will be changed when I install solar on the shed.

Thanks.

 

 

 

Edited October 7 by carlyai
double pic

[Photoguy21]

You can get testers to check which circuit is activating the RCCB. Not sure how much they cost worth looking for one.

[carlyai]

9 minutes ago, Photoguy21 said:

You can get testers to check which circuit is activating the RCCB. Not sure how much they cost worth looking for one.

There's no load connected in the shed CU, only the main circuit breaker is ON, all circuit breakers removed and main breaker trips RCBO.

[Photoguy21]

32 minutes ago, carlyai said:

There's no load connected in the shed CU, only the main circuit breaker is ON, all circuit breakers removed and main breaker trips RCBO.

The instrument I am thinking of is used to check each outlet and it will tell you what the current is. Crossy may well know the name of the device he is more electrical than I am.

[Wanderer555]

RCBO MCB’s can go bad overtime, and require replacement. 😅

[carlyai]

12 minutes ago, Wanderer555 said:

RCBO MCB’s can go bad overtime, and require replacement. 😅

Our garage is hot and probably 100% humidity alot. All metal tools etc go rusty from the humidity me thinks.

Just off to Kuchinari to see if they have a MCB for the garage CU.

 

If not, my stick it in the microway. 🙂

[carlyai]

Replaced the MCB and RCBBO tripped. Bugger.

Tomorrow I'll replace the RCBO with a breaker.

[carlyai]

Just a question on Contact Break Spark Analysis: when the RCBO trips sometimes there is no contact spark visible and sometimes when the contact breakes there is a spark visible.

What sort of current is needed for a contact spark?

 

[carlyai]

I changed the RCBO to a normal 15A breaker and breaker didn't trip but measured 8A with the clamp meter and no pumps etc except the garage MCB on.

Will put this in the 'Too Hard Basket' and go and fix my car back discs while thinking (which is difficult when you're older.) 🙂

 

[degrub]

Not sure i follow everything you wrote, but sounds like a leak to earth. 8 amps is a lot of current for nothing connected/ on. Any chance L and N are reversed going to the shed ?

Edited October 8 by degrub

[Crossy]

1 hour ago, carlyai said:

I changed the RCBO to a normal 15A breaker and breaker didn't trip but measured 8A with the clamp meter and no pumps etc except the garage MCB on.

Will put this in the 'Too Hard Basket' and go and fix my car back discs while thinking (which is difficult when you're older.) 🙂

 

8A is a couple of kW going somewhere!

 

If nothing else it's costing you $$$ and something will be getting warm. 

 

Does your meter actually read zero when there's nothing in the clamp?

 

Have the neighbours tied in somewhere?

 

I note that the stand-alone RCBO is only 15mA, replacing it with a 30mA may solve the tripping issue without compromising safety.

 

[carlyai]

No I checked that.

Before I left to fix my car, I turned off all the garage breakers again with only the garage MCB on and the 8 A went away. When I get back home I will again check every cct. From the garage CU.

What started all this was random tripping of the RCBO. I chased it down to the pool pump motor and changed the start capacitor, which fixed the problem for a few hours, then the intermittant tripping came back.

 

[degrub]

Are the breaker wire clamps specific for Al wire ?
i understand that if not, they need routine tightening and the conductor may tend to creep.

[Crossy]

In order to trace leakage to ground you need an insulation-tester (or "Megger").

 

They do tend to be a one-trick pony and the cheapest I've found is by "Aneng".

 

https://www.lazada.co.th/products/mh12mh13-i5128983639-s21648925185.html?

 

[degrub]

Where’s the crank ? 😀

[Crossy]

38 minutes ago, degrub said:

Where’s the crank ? 😀

 

Pressing the "Test" button of course 🙂 

 

A few (not many) years back I required a supplier to insulation test newly delivered equipment (it was in their Delivery Spec. for flips sake).

 

They turned up with a genuine hand-crank Megger!! It would have been ok but it was out of calibration (by 5 years). 

 

EDIT To prove I'm pure evil (as many members already know).

A favourite trick in a previous life (when I was actually allowed to touch electronics) was to charge up small ceramic capacitors using the megger, then leave them strategically "lying around" in the electronics lab just waiting for an apprentice to pick them up. They kept enough charge for a serious "nip" for several hours!!

 

Amazingly, you can still buy them.

 

[degrub]

1 microfarad caps kept everyone on their toes. 

[carlyai]

First year Telecom. TIT all us country guys stayed in a big boarding house near the Engineering College in Homebush, a suburb of Sydney.

There was about 60 of us pimplly faced young bucks, soon to be introduced to beer, beer, beer, nurses and song.

Someone had a hand cranked ring generator and we all held hands in a circle while someone cranked the handle. The circle would soon be broken. 🙂

[carlyai]

Thank you all very much for your replies.

After returning home I blew out the garage CU again and fiddled around and, like magic, the fault seems to have disappeared, waiting for the worst time to come back again.

I remember when I worked on the remote island of Milingimbi red ants used to cause all sorts of strange electrical problems.

 

 

[carlyai]

As I said before the PEA power first comes to a CU on the wall then used to split with one phase to the garage.

Because the power varies up to 235v and fish tanks in the garage, I installed 220v stabalisers in the house and also a genset and grabbed a house feed (which was to be used for an airconditioner in the lounge room) and replaced unregulated feed with the house regulated feed (that's the cct. breaker to the Al cable).

The only things now on the unregulated power is my 60m aquifer pump and equipment.

I want to also feed the pump etc with regulated supply from the house.

To do this I need to rearrange the Al cable and house feed (yellow conduit) to the pump box.

How do I add pigtails to the Al cable or how to get it to the pump box? 

I know they are dissimilar metals, but Cu pigtails.

The pump controller is showing 230v but does get up to 235v.

 

[carlyai]

Time for a swim   brrrrr.

[Crossy]

10 minutes ago, carlyai said:

How do I add pigtails to the Al cable or how to get it to the pump box? 

I know they are dissimilar metals, but Cu pigtails.

 

You need bi-metal cable splices https://www.aliexpress.com/item/1005004389997423.html

 

[carlyai]

1 hour ago, Crossy said:

 

You need bi-metal cable splices https://www.aliexpress.com/item/1005004389997423.html

 

Would something like this be OK? 

[Crossy]

1 minute ago, carlyai said:

Would something like this be OK? 

 

Looks good to me 🙂 

 

Avoids crimping if you don't have a crimp-tool.

 

[carlyai]

Just ordering a 30mA RCBO and connectors.

Thanks again. :)

[bluejets]

Megger and a lecky who knows how to use it.

[carlyai]

Looks like I need a Megger.

Leakage current now.

 

Edited October 11 by carlyai
Spelling

[degrub]

All devices removed from the circuits ?

 

[carlyai]

1 hour ago, degrub said:

All devices removed from the circuits ?

 

No. I will do that today.

 

[Crossy]

Does your meter actually read Zero with nothing in the clamp?

 

Use the "rel" function to get more accurate readings.