100mA RCD Keeps tripping...

C.R.A.Z.Y said:
An RCD use's a ...
Click to expand...
I was making a post to comment on Sinny's references to neutral leakage.

While what I wrote may be technically less correct than yours it is also slightly more understandable from a conceptual point of view :p

An RCD is better described as an earth leakage detector. If the current flowing through the live and neutral are not in balance it implies some current must be leaking through someone or something to earth. Once detected the RCD trips.
 
A residual current device is designed to protect you from shocks.

It uses the idea that the current in the live and the neutral must be exactly the same. If it isn't then some current, even a very small one, must be leaking to ground somewhere, perhaps through you. A current leaking to ground always indicates a fault so the RCD breaks the circuit.

So what an RCD does is compare the current in the live and the neutral. If they're not identical it trips out.
Click to expand...
 
Water in an external socket? That's a common one.

(no pun intended).
 
Lucero said:
This has made my brain explode.

If it's your drier causing the trip, surely the drier is then off anyway as it has no source of electricity
Click to expand...

Errrrrr no.....
Obviously the drier has an intermittent fault, this then in turns trips the MCB! This fault is still present when the trip is being reset ergo it refuse's to reset until fault is removed from the circuit.
 
C.R.A.Z.Y said:
Clearly as you don't understand how an RCD works tbh!
An RCD use's a differential current transformer to detect the current balance going out of the Phase conductor and returning via the neutral, obviously this should always be equal/sum of zero in an electrically sound ring final/radial.
It's extremely rare for their to be ''unecessary current flowing through the neutral'' as this would require an extra circuit or external influences to create this magical 'extra current'
The vast majority of the time RCD's operate by detecting LACK of current in the neutral.
Click to expand...

Yes, I'm sure the OP knows what a "differential current transformer", and yes I know what an RCD is seeing as I'm training to be an electrician.

checking the balance between line and neutral is the most basic for you can put it without completely confusing the op...

If I'm wrong then sorry, but thats the way I understand it.
 
Last edited:
The vast majority of the time RCD's operate by detecting LACK of current in the neutral.
Click to expand...
No they dont

It uses the idea that the current in the live and the neutral must be exactly the same. If it isn't then some current, even a very small one, must be leaking to ground somewhere, perhaps through you. A current leaking to ground always indicates a fault so the RCD breaks the circuit.
 
MOOGLEYS said:
No they dont

It uses the idea that the current in the live and the neutral must be exactly the same. If it isn't then some current, even a very small one, must be leaking to ground somewhere, perhaps through you. A current leaking to ground always indicates a fault so the RCD breaks the circuit.
Click to expand...

Aye, it should be in a domestic environment 30mA which is tiny.
 
I very common fault that i used to find would be a washing machine getting to a certain point in its cycle which was 'faulty' and this would cause RCD's to trip. I have also had RCD's trip and found, after many hours, that a mouse had chewed through a cable in the floor void. These type of intermittent faults can be a pain for us sparks to find sometimes but my advice is to unplug all non essential appliances and see if you still have the problem. If you do still have problems then it may be time to call a spark in who can test the RCD and all circuits.
 
You must log in or register to reply here.
Back
Top Bottom