RCD tripping when earth core touched

[Keefyjet]

Hi,

As I understand, touching or cutting the earth core of a disconnected (via its MCB) circuit can cause an imbalance and an RCD trip – due to other working circuits connected to the same RCD bank.

So why doesn’t touching the earthed part of a working appliance (e.g. the chassis of a tumble dryer) cause the same imbalance and RCD trip?

Maybe I’m missing something blindingly obvious here – in which case please enlighten me.

Regards.


:21:

 

[markc123]

Nothing to do with other circuits, its because the neutral is common at the neutral bar and MCB's are single pole.

 

[markc123]

Not sure what you mean by touching the chassis of a tumble dryer? Touching with what? Your hand....?

 

[Wonderwall]

Touching an earth core shouldn't trip an rcd.
cutting the cables ( shorting the N & E) usually does

 

[telectrix]

remind me not to fly keefyjet. stick with BA.

 

[Badged01]

Are you sure it is earthed?

If your washing machine body is earthed and on a TN-C-S system the "Earth" and Neutral are effectively the same thing as they join together at the supply feed. You make a connection between your 'washers' CPC and the 'washers' neutral then it allows other circuits current an alternative path back (i.e. some current flows up the 'washers' neutral and down the 'washers' earth so passing the RCD and causing the inbalance).

There are a few assumptions there, the biggest being that you dont have a double pole 'washer' MCB and the neutral is isolated!

 

[Keefyjet]

Not sure what you mean by touching the chassis of a tumble dryer? Touching with what? Your hand....?

Yes, as in providing another earth route, in this case via ones body. Why doesn't it unbalance the system in the same way as touching or cutting through the earth cable?

 

[GMES]

remind me not to fly keefyjet. stick with BA.

Classic Tel :sifone:

 

[Badged01]

remind me not to fly keefyjet. stick with BA.

Even if hes offering free seats in 1st class with the hostesses and booze thrown in ;-) ..... would have said cigars too but that might be too much!

 

[Des 56]

Disclaimer to this thread

Your understanding is appreciated

This new technology is only just a recent introduction to us in Wales

 

[markc123]

Touching an earth core shouldn't trip an rcd.
cutting the cables ( shorting the N & E) usually does

It depends what you touch the earth with, i'm confused aswell by the OP lol.

Stick your manhood on the earth, and you wont trip the RCD and if everythings in working order you won't get the thrill you're probably desiring.

Stick a line conductor on the earth, then you'll trip it.

Mr.Keefyjet what do you mean by touching the metallic frame of an appliance? I hope you're not suggesting, why should it not trip when you pick it up lol

I suggest reading up on earthing and bonding.

 

[telectrix]

some good literature on that very subject by D .W. Cockbum, available from amazon. :carolers:

 

[Badged01]

This new technology is only just a recent introduction to us in Wales

It came as an upgrade with indoor toilets for some reason ......

 

[telectrix]

a pilot project in south wales introduced indoor toilets and bathrooms to a few select houses. when it was found that said toilets and bathrooms were being used to bath and shear the sheep, the project was abandoned in favour of underground housing, but those resourceful taffs kept coming back to the surface bringing up the coal.

 

[Keefyjet]

Yes, the neutral is common but, as I understand it, the imbalance causing the RCD to trip occurs only if one or more of the other circuits under said RCD bank is/are in use? In other words if all of the circuits under the control of that RCD had no load the RCD wouldn't trip as there'd be no imbalance for it to detect?