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 21 hours ago 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 4 hours ago 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.