Dishwasher tripping RCBO

[JohnW2]

What am I missing?

You are missing the fact that there is a high resistance cpc in the wound extension lead which is limiting the fault current to earth so it no longer trips the RCBO.

I find that hard to believe. The most marginal situation would be that of a fault current of exactly 30mA (without extension lead), corresponding to a L-E fault of approx. 8,000Ω (it's much more complicated with N-E faults, so I won't consider that possibility ). The CPC of even a 50 metre 1.25mm² extension lead would be (just) under 1Ω - so the chances of the fault being so marginal that it would operate the RCBO without the extension lead, but not with it (due to the extra 1&#937, would surely be incredibly small?

Kind Regards, John.

 

[ColJack]

my guess, water / damp causing a N-E short..
nothing plugged in means not much current running down that leg to cause a big enough N-E current.. with the dishwasher in then there's more current in the leg so more can leak..

have a look in the socket and see if it's wet / damp... ( with the power off.. )

 

[JohnW2]

I was thinking high impedance neutral.- loose, burnt.

Yes, but a high resistance neutral would not, in itself, cause an RCBO to operate; as I said, I think you'd need a second fault for your idea to work.

IHowever, mfarrow's idea is good.

I'm very far from convinced - see my response to him/her.

Kind Regards, John.

 

[JohnW2]

my guess, water / damp causing a N-E short.. nothing plugged in means not much current running down that leg to cause a big enough N-E current.. with the dishwasher in then there's more current in the leg so more can leak..

I don't really get that theory. Provided the neutral of the circuit are intact, I would have thought that plugging in the load to any socket on the circuit would result in essentially the same (very small) rise in neutral potential at the 'suspect' socket (hence rise in N-E fault current, if there is a N-E fault).

Kind Regards, John.

 

[EFLImpudence]

Perhaps there is no earth in the extension lead.

 

[JohnW2]

Perhaps there is no earth in the extension lead.

That would obviously be an answer, but (unless due to a fault) AFAIAA the only ones of those are those intended for use with Class 2 garden tools etc - and, unless modified, would not have the right sort of socket for a dishwasher It surely cannot be allowed, or compliant with the relevent Standard, to have a 2-core extension lead with a BS1363 socket on the end of it?!

Kind Regards, John.

 

[ban-all-sheds]

I only have led torch from my mobile.

Get one of these: