Another RCBO tripping

[Susco]

I enable breaker from aircon, it is open by default because I never use aircon in that room, open the aircon and after about 10 minutes the RCBO trips.

 

Since then I just enable the breaker, without the aircon running, and after 15 seconds RCBO trips each time.

 

Where should I start looking?

[Metropolitian]

Is it a plain breaker or a RCBO.

 

Many breakers for the aircons here in Thailand do look like those :

 

And RCBO's come in many forms and sizes, they share one specific thing and that's having an -TEST- button.

[RichCor]

Personally I'd suspect a bad breaker and suggest you disconnect the load wire and see if it still trips.

[Susco]

9 minutes ago, RichCor said:

Personally I'd suspect a bad breaker and suggest you disconnect the load wire and see if it still trips.

If I disconnect the load wire from the breaker the rcbo obviously can not trip any more, or do I miss something?

 

But how would that determine if the breaker is bad or not?

[Metropolitian]

 

1 hour ago, Susco said:

I enable breaker from aircon, it is open by default because I never use aircon in that room, open the aircon and after about 10 minutes the RCBO trips.

 

Since then I just enable the breaker, without the aircon running, and after 15 seconds RCBO trips each time.

 

Where should I start looking?

 

 

I can read this in two ways:

 

Breaker for the aircon on the wall turned on (enabled) and it turned on the aircon for 10 minutes and then the RCBO in the consumer unit tripped.

And after that, without operating the aircon, by turning the breaker for the aircon on the RCBO in the consumer unit tripped.

   ->  The breaker has probably failed, it worked for ten minutes and then something inside the breaker went bad and consequentially tripping the RCBO in the consumer unit.

   = replace the breaker (but do read the footnote * )

 

The breaker on the wall, and assumed as an RCBO which it probably isn't (but not impossible because RCBO themself CAN be used as an 'breaker-on-the-wall' for aircons), trips after ten minutes of operating of the aircon and afterwards failing after 15 seconds then the story is the same as above = replace the breaker/rcbo.

 

* There is another possibility and that's when the problem is in the feed from the breaker to the aircon or at the aircon itself.

To eliminate that probability you could disconnect the wire going to the aircon at the breaker.

If problem persist, it is the breaker.

If there's no tripping, do check the wiring and the terminals at the aircon.

 

[Susco]

There is no breaker on the wall, we are talking here about a proper consumer unit with ABB MCB's and a RCBO

[sometimewoodworker]

5 minutes ago, Metropolitian said:

The breaker on the wall, and assumed as an RCBO which it probably isn't (but not impossible because RCBO themself CAN be used as an 'breaker-on-the-wall' for aircons)

A stand-alone RCBO on the wall isn’t at all difficult to imagine. They look very similar to the switches at the top in your first picture and are around 350 baht depending on the rating. The test button is the only giveaway from a distance. I use one as an on/off switch on my homemade polishing wheel and wire brush, it’s probably unnecessary but the difference in cost is minimal.

[Metropolitian]

8 minutes ago, Susco said:

There is no breaker on the wall, we are talking here about a proper consumer unit with ABB MCB's and a RCBO

 

(MAKE SURE THE ELECTRIC IS OFF AND DO SO EACH NUMBERED STEP)

 

1. check the wiring and connection at the terminal in the aircon

 

test..

 

If trips, then

 

2. disconnect the wiring in the aircon and tape off the ends.  (to eliminate the problem being inside the aircon or outdoor unit itself)

 

test..

 

If trips, then

 

3. Check the wiring/connection and the rcbo in the consumer unit (discoloration of the rcbo/loose screws/burn marks/molten insulation at the terminals)

 

Looks good?

 

4. Disconnect the wiring from the RCBO, that goes to the aircon, in the consumer unit (to eliminate the problem in the wiring from CU to the AC)

 

test..

 

If trips, then

 

5. Replace the RCBO.

 

 

[Metropolitian]

If we are talking about two separate breakers in the consumer unit, the one being the RCBO and the other the breaker then..

 

 

 

3. Check the wiring/connection and the breaker in the consumer unit (discoloration of the breaker/loose screws/burn marks/molten insulation at the terminals)

 

Looks good?

 

4. Disconnect the wiring from the breaker, that goes to the aircon, in the consumer unit (to eliminate the problem in the wiring from CU to the AC)

 

test..

 

If trips, then if behind the RCBO are more breakers and the RCBO works fine with them, then..

 

5. Replace the breaker.

[Metropolitian]

2 hours ago, Susco said:

Where should I start looking?

It would be good for us to help you if you provided us with a photo of the actual consumer unit (front and later we can ask for the inside if you are able to handle that) and the aircon.

[RichCor]

29 minutes ago, Susco said:

If I disconnect the load wire from the breaker the rcbo obviously can not trip any more, or do I miss something?

 

But how would that determine if the breaker is bad or not?

 

The 'trip' could be indicative of an actual fault, a failing breaker, or a nuisance (indeterminate) borderline fault.

 

Without proper test gear we are forced to resort to simplified order elimination or replacement and hope when the issue stops being an issue we've solved it (and not buried the fault to later bite us in the a$$).

 

Metropolitian seems to have you covered for the moment.

[Susco]

11 minutes ago, Metropolitian said:

If trips, then

 

5. Replace the RCBO.

There is no wiring that goes from the RCBO to the aircon, wiring goes from the MCB to the aircon. There are 12 MCB's behind that specific RCBO..

 

I have to say that occasionally the  RCBO has tripped spontaneously in the past, without the aircon breaker engaged, but then I just switch on again and it may trip again in a month or two

 

Edit to correct without

Edited May 21, 2020 by Susco

[Metropolitian]

3 minutes ago, Susco said:

There is no wiring that goes from the RCBO to the aircon, wiring goes from the MCB to the aircon. There are 12 MCB's behind that specific RCBO..

 

I have to say that occasionally the  RCBO has tripped spontaneously in the past, without the aircon breaker engaged, but then I just switch on again and it may trip again in a month or two

 

Edit to correct without

Check post #9 ????  a follow up of the steps mentioned in post #8 but #9 is now the right list for you.

It -can- be the faulty breaker (MCB) that cause the RCBO trip.

 

As you said there's 12 MCB's behind that one RCBO and in normal use it only trips once in a month or two then for now we should look at the MCB for the aircon or the wiring to the aircon.

So again check the steps in post #9 to eliminate the fault from end to begin.

[KMartinHandyman]

Last time this came up recently it was a loose wire connection on the back of the rcbo if I remember correctly. Days of speculation before pulling the breaker and seeing the back scorched a little. 
You can see the thread in the electrical forum. 

[Susco]

14 minutes ago, Metropolitian said:

4. Disconnect the wiring from the breaker, that goes to the aircon, in the consumer unit (to eliminate the problem in the wiring from CU to the AC)

 

 

I don't have the consumer unit open right now, but if I remember correctly, all breaker at the bottom are interconnected by a bus bar, and at the top are all the red wires.

 

The red wire is the one that I have to disconnect, right?

 

 

[RichCor]

a photo of the CU with the cover off would make troubleshooting a tad easier (and safer).

[Metropolitian]

37 minutes ago, Susco said:

 

I don't have the consumer unit open right now, but if I remember correctly, all breaker at the bottom are interconnected by a bus bar, and at the top are all the red wires.

 

The red wire is the one that I have to disconnect, right?

 

 

Correct. The red wire is the one to disconnect then.

 

That way we can check the disturbance solely from the MCB. Which is in step 4.
Try step 1 and 2 first, which can be done without opening the CU.

 

After step 1 and 2 if problem still persist then proceed with step 3 (Opening the CU and here do check the screw terminals at the busbar side too, tighten it) and so on.

[Crossy]

Something that I don't think has been mentioned is the possibility of a N-E fault on the load side of the RCBO.

 

These can cause all sorts of interesting random effects and lead you in circles.

 

@Susco do you have any test gear (multimeter)?

 

And as noted, photos of what we have are very useful.

[bankruatsteve]

Also one of the primary causes for mysterious happenings is ants/gecko getting into the equipment.  Take the top cover off the AC and check for that.  Any outside outlets?

[Susco]

3 hours ago, Crossy said:

Something that I don't think has been mentioned is the possibility of a N-E fault on the load side of the RCBO.

 

These can cause all sorts of interesting random effects and lead you in circles.

 

@Susco do you have any test gear (multimeter)?

 

And as noted, photos of what we have are very useful.

 

I have a multimeter, but it has been in use for 8 years, and I always let this aircon run for a few hours every month as maintenance.

 

Can such a N-E fault start years after installation?

[lopburi3]

10 minutes ago, Susco said:

Can such a N-E fault start years after installation?

They normally do.  Rat bite is very common way it happens as they like to bite into warm wires and if exposed wire goes to ground you have a fault (and often intermittent in such cases).

[Crossy]

9 minutes ago, lopburi3 said:

They normally do.  Rat bite is very common way it happens as they like to bite into warm wires and if exposed wire goes to ground you have a fault (and often intermittent in such cases).

 

Cute little chaps aren't they ????

 

[Susco]

8 minutes ago, Crossy said:

 

Cute little chaps aren't they ????

 

How do I check for N-E fault?

[lopburi3]

4 minutes ago, Crossy said:

 

Cute little chaps aren't they ????

 

They really loved our previous two dishwashers from Germany.  No issues with current (cheaper) Electrolux.  Also had one eat in attic both L/N so they occasionally touched (no ground fault) and tripped actual breaker.  Perhaps a reason to make home cat friendly.

[bankruatsteve]

8 minutes ago, Susco said:

How do I check for N-E fault?

Open outside outlets.  If you find critter debris, that can/will create N-E or L-E fault when the humidity gets up there.  Same for the compressor.  Those are just the obvious ones and do not require instrument.  Otherwise, testing can get a bit tricky.

[sometimewoodworker]

18 minutes ago, Susco said:

How do I check for N-E fault?

You usually find it by the RCCD tripping and if it does look for the trip flag to have changed colour or possibly by checking the temperature of it. If warm to hot it is probably an overload trip if cool it’s likely to be an imbalance trip.

 

an overload trip will not change the flag colour.

[Metropolitian]

4 hours ago, Crossy said:

Something that I don't think has been mentioned is the possibility of a N-E fault on the load side of the RCBO.

 

These can cause all sorts of interesting random effects and lead you in circles.

Not directly mentioned but would be if issues with the breakers are eliminated as -not- being he cause.

Hence the steps I mentioned to rule out some parts of the circuits.

 

Example: If the wires are disconnected at the aircon, and no tripping occurs then we would need to look at N-E issues at the indoor unit (terminals and mainboard for foreign objects) and the outdoor unit. 

 

Easier to do that, especially if the wiring is tucked away in the wall/ceilings.

 

4 hours ago, Crossy said:

And as noted, photos of what we have are very useful.

The consumer unit mush be blushing by now as several people has asking a photo from it ????

[Metropolitian]

37 minutes ago, Crossy said:

 

Cute little chaps aren't they ????

 

You can come to pick up mine for free.  ????

 

 

[Metropolitian]

29 minutes ago, Susco said:

How do I check for N-E fault?

That's included in the steps ???? Once we knew where in the circuit the problem is we can focus on that.

[Crossy]

18 minutes ago, Metropolitian said:

The consumer unit mush be blushing by now as several people has asking a photo from it ????

 

Yeah, with it's cover removed too ????