RCD trips when I switch off

[Racundra]

The RCD sometimes trips (3 or 4 times in two weeks) when I switch off at a particular wall socket. My computer’s plugged in there, via a surge-protection socket. I always shut the computer down using the Windows ‘turn off’ menu, then when it’s stopped, I switch off at the wall. It’s that last action that seems to trip the RCD.
I’ve only a sketchy knowledge of RCDs, but it seems odd to me that it trips when switching off, not on. This problem began after I installed a new power supply unit in the computer, but that’s stopped running by the time I switch off at the wall. House wiring is only 4 years old.
Any thoughts please?

 

[securespark]

The only time I solved a conundrum like this was after I had done a board change.

It was a "16th" split board. Upon switching the main switch OFF, the RCD tripped.

I found a NE reversal at the plug top of a freezer.

Odd.

 

[JohnW2]

The RCD sometimes trips (3 or 4 times in two weeks) when I switch off at a particular wall socket. My computer’s plugged in there, via a surge-protection socket. I always shut the computer down using the Windows ‘turn off’ menu, then when it’s stopped, I switch off at the wall. It’s that last action that seems to trip the RCD.
I’ve only a sketchy knowledge of RCDs, but it seems odd to me that it trips when switching off, not on. This problem began after I installed a new power supply unit in the computer, but that’s stopped running by the time I switch off at the wall. House wiring is only 4 years old.

Doing a 'soft' turn-off, using Windows, does not completely shut down the power supply - it's like a 'Standby' mode.

What happens if, having done the soft shutdown, you switch off the computer's power supply with the switch on it? Does the RCD then immediately trip? If not, does it then trip when you switch off the socket?

Kind Regards, John

 

[ricicle]

A simple check solution would be to try replacing the wall socket. An older one might be worn so the switch isn't breaking cleanly or evenly (if double pole)

 

[securespark]

MK DP switches are never even. The neutral makes first and breaks last.

 

[ricicle]

Possibly more of a debouncing issue then on one or both poles.

 

[Racundra]

Thanks to all.
JohnW2: I'd forgotten about the switch on the power unit itself. I used that several times & it was OK. Then I used the wall switch and it tripped.
Ricicle: I'll try another wall socket next.

 

[JohnW2]

JohnW2: I'd forgotten about the switch on the power unit itself. I used that several times & it was OK. Then I used the wall switch and it tripped.
Ricicle: I'll try another wall socket next.

In that case, before you go changing the wall socket ...do I understand that you have some sort of 'anti-surge' device between the computer and the wall socket? If so, what happens if you remove that from the setup?

Kind Regards, John

 

[Racundra]

JohnW2: thanks. It's a trailing set of sockets with surge and spike protection. I've had it a couple of years with no problem, but I'll remove it & see what happens. This being an intermittent fault, it may take a while!

 

[JohnW2]

JohnW2: thanks. It's a trailing set of sockets with surge and spike protection. I've had it a couple of years with no problem, but I'll remove it & see what happens. This being an intermittent fault, it may take a while!

In that case, are there any other things (other than the computer) plugged into that set of trailing sockets? If there are, then your first experiment probably ought to be to see if tripping still occurs if they are unplugged before you operate the wall switch.

Kind Regards, John

 

[Peet]

There's a B16 RCBO ( a 16A breaker combined with a 30mA RCD) here that does the same thing. I've never stopped to investigate it as it forms a temporary supply which will go soon. The only load on it is a 3.3kVA 110V transformer. I don't think I've ever known it trip when switching off using the switch on the socket, but switch off by pulling the plug out of the socket and it will trip maybe once every 10-15 or so times. I'd just put it down to a noisy breaking of contacts when done by hand, or maybe the RCD was overly sensitive.

Its appearance your end, coinciding with a power supply change in the PC maybe for a number of reasons. Like JohnW2 says 'off' is only nearly off. ATX power supplies have a +5v standby voltage on them which is used for a number of features. Besides these the input filtering capacitors/input rectifier and main input capacitor will all remain in circuit regardless of the power supplies state. It could be that this combination on the new power supply with a noisy breaking of contacts causes larger current spikes on the power line which unsettles the RCD.

I'd guess that the input filtering capacitors, going from line to earth and neutral to earth may also play a part in it perhaps?

 

[Spark123]

There's a B16 RCBO ( a 16A breaker combined with a 30mA RCD) here that does the same thing. I've never stopped to investigate it as it forms a temporary supply which will go soon. The only load on it is a 3.3kVA 110V transformer.

One thing I do know is when I plug my 3.3kVA yellow box in it often trips the B16 MCB owing to the initial pulse of startup current. Maybe when you unplug it is causing a make/break situation hence going above the 80A momentarily thus causing it to trip on over current as opposed to earth leakage.

 

[Racundra]

I've taken the surge protector out of the setup; no trips yet! (I've used it without problem for a couple of years -- but I moved house 4 months ago; the RCD in this house is more modern and therefore perhaps much more sensitive).
I've also tried unplugging the printer, the display, etc etc, and a different wall socket, in various combinations -- all without any trips. There may be a solution somewhere in all that, and again there may not! Pants to intermittent faults!
Thanks to all contributions -- much appreciated.