RCD tripping

[Susco]

Every now and then, like once every one or two months, I wake up to tripped RCD.

 

It is the circuit that has the pool pumps and the irrigation pumps on it, but also the kitchen sockets.

 

I don't know the exact time that it trips, but going by the temperature the freezer has at the time I wake up, I suspect it trips when the pool pump starts.

 

The strange thing is that there is also a safe-T-cut RCBO in the pool pump house, but that one doesn't trip.

 

The safe-t-cut RCBO in the pump house is adjustable from 6 to 30, and is set at the 30. If I move to a lower setting, it may trip.

 

Any idea what I'm looking at?

[BritManToo]

14 minutes ago, Susco said:

Any idea what I'm looking at?

Faulty (or oversensitive) RCD.

[bankruatsteve]

Where is the RCD that trips and what setting?  A trip once in a couple months is not likely easy to sleuth.  First guess would be effects from humidity.

 

[Susco]

3 minutes ago, bankruatsteve said:

Where is the RCD that trips and what setting?  A trip once in a couple months is not likely easy to sleuth.  First guess would be effects from humidity.

 

 

The one that trips is in the main breaker box in the house, and is 63A ABB RCD with a 30mA sensitivity

[Crossy]

1 hour ago, Susco said:

The safe-t-cut RCBO in the pump house is adjustable from 6 to 30, and is set at the 30. If I move to a lower setting, it may trip.

 

Leaky something on the pump house circuit.

 

With two RCBOs cascaded it's impossible to determine which will go first even if one is set to a lower current than the other.

 

Is it possible to move the pump house so that it's not fed from the house RCBO? It will still be protected by its own RCBO but it won't be taking out the freezer.

 

Can you post a photo of the main CU with the lid off so we understand exactly what you have?

[Susco]

4 minutes ago, Crossy said:

 

Is it possible to move the pump house so that it's not fed from the house RCBO? It will still be protected but it won't be taking out the freezer.

 

 

I think that would be a difficult job, because the 2 breakers that feed the pump house are almost next to the RCD.

 

If I want to do that, I assume I will have to move them to the end of the circuit, so that I can give them their own feed, but I guess that may create issues with the length of the wires, and that would be a job for a qualified electrician.

[Crossy]

Alternatively, could you move the freezer to feed from before either of the RCDs?

 

[bankruatsteve]

If the main RCBO is tripping, how do you correlate that to the pump circuit?

[Crossy]

1 minute ago, bankruatsteve said:

If the main RCBO is tripping, how do you correlate that to the pump circuit?

 

Assumption. If he turns down the pump RCBO it trips. 

 

The real fix is to find the leak in the pump circuit and avoid cascading RCDs.

[Susco]

5 minutes ago, Crossy said:

Alternatively, could you move the freezer to feed from before either of the RCDs?

 

 

That would be even more complicated. I have 3 breaker boxes on top of each other, each with their own RCD.

 

The pump house and the kitchen sockets are in the top one, and there I have space for 3 more breakers.

 

So I would have to move the kitchen sockets to a lower box, but they have their rails completely full.

 

 

[Crossy]

OK, are there any "risky" (water heaters, outside outlets etc.) circuits in the top box?

 

If not just replace the RCD with a regular MCB, the pool stuff is still protected by it's local RCBO.

 

You could shuffle the top box to put the RCD half way along making a split box one side with no RCD.

[bankruatsteve]

2 minutes ago, Susco said:

The pump house and the kitchen sockets are in the top one, and there I have space for 3 more breakers.

One option would be to replace the RCBO with a MCB.  Assume the freezer on the kitchen circuit?

[Crossy]

Great minds there @bankruatsteve

[Susco]

6 minutes ago, Crossy said:

OK, are there any "risky" (water heaters, outside outlets etc.) circuits in the top box?

 

If not just replace the RCD with a regular MCB, the pool stuff is still protected by it's local RCBO.

 

You could shuffle the top box to put the RCD half way along making a split box one side with no RCD.

 

The same circuit feeds 2 aircons, 2 water heaters and the maids quarters.

 

Moving the pump house breakers to the left, before the RCD, may be an option

 

 

[Crossy]

3 minutes ago, Susco said:

Moving the pump house breakers to the left, before the RCD, may be an option

 

Sounds like the best option.

Don't forget to move the relevant neutral(s) to before the RCD too.

[bankruatsteve]

2 minutes ago, Susco said:

The same circuit feeds 2 aircons, 2 water heaters and the maids quarters.

Hmm.

[Susco]

Just now, Crossy said:

 

Sounds like the best option.

Don't forget to meove the relevant neutral(s) to before the RCD too.

 

That was supposed to be my next question.

 

How do I find which are the relevant neutrals?

[Susco]

Just now, bankruatsteve said:

Hmm.

?

[Crossy]

Just now, Susco said:

How do I find which are the relevant neutrals?

 

In a typical Thai installation - use a crystal ball ???? 

 

Probably easiest would be to turn off the power, pull all the neutrals from the neutral bar, apply a L-N short in the pump house and look for the neutral thats shorted to the L in the box.

 

[bankruatsteve]

The water heaters and the maid quarters are in the top box also?  You don't suspect either of those causing the RCD trip?

[Susco]

Just now, bankruatsteve said:

The water heaters and the maid quarters are in the top box also?  You don't suspect either of those causing the RCD trip?

 

No because the breakers from the water heaters are open, the respective aircons are not running, and the maids quarters have never been occupied lol

[lopburi3]

1 hour ago, Crossy said:

 

Leaky something on the pump house circuit.

 

With two RCBOs cascaded it's impossible to determine which will go first even if one is set to a lower current than the other.

 

Is it possible to move the pump house so that it's not fed from the house RCBO? It will still be protected by its own RCBO but it won't be taking out the freezer.

 

Can you post a photo of the main CU with the lid off so we understand exactly what you have?

As said above - the upstream RCD will have additional leakage so will likely always trip first if both set at 30.  The "fact" that you can not run the pump RCD below 30 without trip indicates fault in pump circuit and probably time to replace.  You do not want to take any chances around pools/electric.

 

[carlyai]

19 hours ago, Crossy said:

 

In a typical Thai installation - use a crystal ball ???? 

 

Probably easiest would be to turn off the power, pull all the neutrals from the neutral bar, apply a L-N short in the pump house and look for the neutral thats shorted to the L in the box.

 

Turn off all the breakers except the pump breaker. Start the pump. Remove each neutral until the pump stops. 

[Crossy]

36 minutes ago, carlyai said:

Turn off all the breakers except the pump breaker. Start the pump. Remove each neutral until the pump stops. 

 

That would work, bit it's a bit risky for someone not used to live working.