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Fuse box/trip switch question


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Can anybody explain the purpose of this please.

 

What does it do? What is it for? And why do I need to press it once a month?

Please be gentle with me I know nothing..............

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Posted (edited)
20 minutes ago, carlyai said:

Because the RCBO is an electro-mechanical device it can fail and you wouldn't know that your house is not protected, so you can test it monthly to make sure it's working.

And when you press that little button the switch should go off and then you don't have any electricity anymore (in your house). That's the way it's supposed to work.

So make sure you don't do that in the dark.

If it switches off the way it's supposed to then you can just press the lever up again and the light will go on again.

On some of these things the lever needs a lot more pressure than you might think it needs. That is normal.

 

And if you press that small button and nothing happens then that is bad. Then the protection does not work. And then it's time to talk to an electrician ASAP to get this fixed.

Edited by OneMoreFarang
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The circuit diagram on the RCBO is misleading.

When the button is pressed a small electric current should flow to earth through the limiting resistor. 

A current loop connected to the trip sense coil will detect this imbalance of current between the live and neutral wires and cause the MCB to trip.

The button needs to be pressed every month to test this function.

 

As Carlyai said it will save you from getting toasted 🙂

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Okay I think I understand.

Many thanks for everybody's explanations.


It tripped out last night (blue button popped out and main switches were down) for no apparent reason and when I tried to reset it the switch would not stay up.

So what might cause this (apart from the toaster) and what is the correct way to reset it?

I should add that this has happened on two occasions in the last 10 days.
Once when we were asleep and the fan stopped working.
And again last night when I was cooking dinner.

I get that using an oven and other appliances might cause an overload but not in the middle of the night with only two fans going.

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3 minutes ago, mrjohn said:

Okay I think I understand.

Many thanks for everybody's explanations.


It tripped out last night (blue button popped out and main switches were down) for no apparent reason and when I tried to reset it the switch would not stay up.

So what might cause this (apart from the toaster) and what is the correct way to reset it?

I should add that this has happened on two occasions in the last 10 days.
Once when we were asleep and the fan stopped working.
And again last night when I was cooking dinner.

I get that using an oven and other appliances might cause an overload but not in the middle of the night with only two fans going.

My immediate thought is rodents.

To verify, you will need to do a visual survey of the places where rats can access your house wires.

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10 minutes ago, mrjohn said:

I get that using an oven and other appliances might cause an overload but not in the middle of the night with only two fans going.

It likely tripped not because of an overload but because the current didn't go where it should go.

The reason could be a damaged cable, or moisture, a (little) faulty device, etc.

The reason could also be that the RCBO does not work correctly, maybe it's too sensitive.

 

It seems you are not the electric specialist and for that reason you could make dangerous mistakes if you try to fix this yourself. Better hire an electrician, and a real one who knows what he is doing.

 

First thing you could do is switch off some devices like your fan and look if the problem only happens if the fan is on.

 

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22 minutes ago, sometimewoodworker said:

Good layman’s explanation though one key word is incorrect.
 

I have 3 protecting different areas 1 has just failed the monthly test and been replaced.

I keyboarded 'can' as most people won't test monthly or regularly. 'Should' is still as vague as 'can', maybe you meant "must". 🙂

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13 minutes ago, Muhendis said:

My immediate thought is rodents.

To verify, you will need to do a visual survey of the places where rats can access your house wires.

OR red ants. Or vibrator motor failure (VMF). 🙂

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18 minutes ago, carlyai said:

I keyboarded 'can' as most people won't test monthly or regularly. 'Should' is still as vague as 'can', maybe you meant "must". 🙂

Should is more positive than can, while must is rather too definite and IMHO not really accurate as a failure to test doesn’t, in itself, cause a problem.

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24 minutes ago, carlyai said:

OR red ants. Or vibrator motor failure (VMF). 🙂

Yeah.

I had a 2,000 Baht bill because of what the red ants did to my fridge control board. 

Although they didn't cause the RCBO to trip they did manage to fry the electronics by shorting themselves between the incoming live track/trace to the low voltage electronics.

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37 minutes ago, OneMoreFarang said:

 

It seems you are not the electric specialist Better hire an electrician, and a real one who knows what he is doing.

 

 

 

I confessed right at the beginning that I know nothing about electricity, so I have no intention of trying to fix it myself.

 

I like the idea of any sort of technician in Thailand who "knows what he's doing"

 

I've been looking for one of those for years.

 

An "electrician" changed this particular trip switch about six months ago.

 

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To reset these beasties, press the blue button back in, then just turn on the main.

 

If it trips again, switch off all your other breakers and try again.

 

Assuming it stays on then turn on the breakers one at a time until it trips, you then need to investigate that circuit.

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