Laptop Power Supplies Trip RCD

ArchieB68 · Feb 25, 2022

Hi,

The RCD which protects my 16A ring main always "trips" when I plug/unplug a Laptop power supply. No other type of appliance causes a problem. I have 2 laptops with the external power supplies on leads which both cause this problem. I also have a similar 240v to 12v switching adaptor for a mini fridge which will trip the RCD too.
I've had an electrician look at it but he couldn't find the problem. He replaced the RCD for the bank that the ring main is connected but it made no difference.
When the RCD trips it takes out everything on that bank including lights and heating circuit. The consumer unit has two banks protected by two separate RCD's. The MCB on the ring main appears to be working properly.

Has anyone seen anything like this? If we leave the laptop supplies plugged in permanently then there is no problem. It's only when we try to relocate the plug to a different socket that the RCD trips.

Many thanks, Archie

pc1966 · Feb 25, 2022

Is it the act of plugging in, or when you switch the socket on, that causes the trip?

My suspicion would be on the plug/cable of the PSU being at fault. Have you got another mains cable (assuming it is "cloverleaf" style)?

littlespark · Feb 25, 2022

It could be cumulative earth leakage from the chargers… along with everything else on the rcd.

Does it only happen in one socket? Did the electrician check the cables behind it?

ArchieB68 · Feb 25, 2022

pc1966 said:
Is it the act of plugging in, or when you switch the socket on, that causes the trip?

My suspicion would be on the plug/cable of the PSU being at fault. Have you got another mains cable (assuming it is "cloverleaf" style)?

It's only when the plug is inserted. The socket can be on or off, it doesn't matter. I have three different power supplies that cause this problem and friends laptops cause the RCD to trip as well. I've had these cables PAT tested and they have all passed. I'm pretty confident that the fault is in the house. I've also used these cables in friends houses and they don't cause a problem there.

ArchieB68 · Feb 25, 2022

littlespark said:
It could be cumulative earth leakage from the chargers… along with everything else on the rcd.

Does it only happen in one socket? Did the electrician check the cables behind it?

It can happen on any socket on the ring main.

Avo Mk8 · Feb 25, 2022

There will be EMI filters on those power supplies (see below)
The act of plugging them in (even without switching on) connects a capacitor between N and E (amongst other things).
If you aleady have leakage on that ring, the surge due to connecting the uncharged filter capacitor might just be responsible, but it's likely there is something else amiss.
If you unplug absolutely everything else from the ring, does it still do it?

[ElectriciansForums.net] Laptop Power Supplies Trip RCD

ArchieB68 · Feb 25, 2022

Avo Mk8 said:
There will be EMI filters on those power supplies (see below)
The act of plugging them in (even without switching on) connects a capacitor between N and E (amongst other things).
If you aleady have leakage on that ring, the surge due to connecting the uncharged filter capacitor might just be responsible, but it's likely there is something else amiss.
If you unplug absolutely everything else from the ring, does it still do it?
View attachment 95438

When I unplug everything on the ring and then plug in one of the laptop power supplies it can still trip the RCD. It's not 100% repeatable though. Sometimes we can go weeks without tripping then it will happen every time we plug/unplug a supply. I think littlespark is correct and it's a cumulative earth leakage.

Avo Mk8 · Feb 25, 2022

ArchieB68 said:
When I unplug everything on the ring and then plug in one of the laptop power supplies it can still trip the RCD. It's not 100% repeatable though. Sometimes we can go weeks without tripping then it will happen every time we plug/unplug a supply. I think littlespark is correct and it's a cumulative earth leakage.

I agree. If you could beg/borrow a sensitive clamp leakage detector, you might find what is contributing to 'cumulative'.

LastManOnline · Feb 26, 2022

ArchieB68 said:
It's only when the plug is inserted.

I suspect there is, nt anything "wrong" per say. Inrush current is a feature of every electrical circuit. The natural leakage built in to the appliances you are using will also experience a momentary spike when initially plugged in. Usually rcd, s can cope with this but in your case there is obviously another (and very inconvenient) factor at play