Trip MCB at times RCD too intervals days or hours; test if faulty appliance

[MattyA]

Hi
I am asking for help as a novice and 1st time user of this forum.
Recently started to experience tripping of MCB & sometimes with the RCD at random times, intervals can be days after resets or several hours.
Could an appliance or appliances be overloading the circuit?
How can I test an appliance to see, if it faulty and a cause of the MCB/RCD tripping?
What equipment is needed to test appliances such as Fridge, Rice Cooker, Electric heater, Fan etc for an MCB/RCD tripping?

At present all I have is a multi-meter.

Thank you in advance for any advice you can offer?

 

[littlespark]

MCB's and RCD's work different ways.

An MCB is like an old fuse in as much as it turns off if there is an overload, or overcurrent.

An RCD trips off if there is an earth fault. Basically compares what is running through live is the same as neutral... which it should be.
If theres a difference (say, 30mA) then it trips off, because that 30mA may be running through a human body

An RCBO is a device which is an RCD and MCB combined.



Any chance of a photo showing the board and which mcb/rcd are tripping off?

 

[UNG]

In a lot of cases I find random trips are down to fridges or freezers and the auto defrost cycle, the cause is usually a failed defrost heater that can only be properly tested by taking the appliance apart and testing the heating element

 

[MattyA]

Hi
I am asking for help as a novice and 1st time user of this forum.
Recently started to experience tripping of MCB & sometimes with the RCD at random times, intervals can be days after resets or several hours.
Could an appliance or appliances be overloading the circuit?
How can I test an appliance to see, if it faulty and a cause of the MCB/RCD tripping?
What equipment is needed to test appliances such as Fridge, Rice Cooker, Electric heater, Fan etc for an MCB/RCD tripping?

At present all I have is a multi-meter.

Thank you in advance for any advice you can offer?

 

[MattyA]

MCB's and RCD's work different ways.

An MCB is like an old fuse in as much as it turns off if there is an overload, or overcurrent.

An RCD trips off if there is an earth fault. Basically compares what is running through live is the same as neutral... which it should be.
If theres a difference (say, 30mA) then it trips off, because that 30mA may be running through a human body

An RCBO is a device which is an RCD and MCB combined.



Any chance of a photo showing the board and which mcb/rcd are tripping off?

Hi LittleSpark,
I am new to Forums in general and sent an image to myself as way of putting it up there. Just noticed I can reply to you directly too.

 

[MattyA]

In a lot of cases I find random trips are down to fridges or freezers and the auto defrost cycle, the cause is usually a failed defrost heater that can only be properly tested by taking the appliance apart and testing the heating element

I too suspect the fridge freezer... I wondered if a PAT test equipment would reveal if it was faulty. Thank you for taking the time to give me your thoughts.

 

[UNG]

I too suspect the fridge freezer... I wondered if a PAT test equipment would reveal if it was faulty. Thank you for taking the time to give me your thoughts.

Because the defrost timer resets when the power is lost and it removes the defrost heating element from the circuit a PAT test will not find the problem so as mentioned in a previous post you have to find where it is in the fridge and physically test it

 

[littlespark]

I don’t see an rcd here. Is it elsewhere, supplying this board?

It looks like it’s in a garage… is there excessive moisture getting into anything?


I’m afraid, the only way to know for sure is to unplug the suspect appliance and see if it holds over time.