Flash and bang turning granny charger off

Hi PH'rs

I've owned my Rav4 PHEV for a week and until Octopus give me a charge point installation date I'm using the Toyota supplied granny charger. Priot to picking which socket I used I plugged in my socket tester and also checked the plug and socket for increased heat during its use. Nothing flagged....

Until today!

My car was charging using the granny charger and not on an extension for an hour. I went to check for any heat on the plug and there was none of concern. As I needed to go out I went to turn the switch off at the granny charger and there was an almighty flash from the switch and a bang. Fortunately it tripped the RCD so I didn't get a shock.

My house has reasonably modern wiring, a new consumer unit and Solar plus battery (Not that I expect the solar contributed to this).

I have no idea what caused the flash, bang and tripping of the RCD. Its not as if I unplugged the charger from the socket without turning the socket off first.

Im trying to avoid this happening again so I would like to hear any suggestions as to what may have happened?

Is the socket double pole? Is it a waterproof type?
It would be best with an RCD plug on (or in line to) the charger.

If the flash was from the socket switch, you need a new socket.

If the flash was from some part of the granny charger, it's faulty.

Does the manual suggest stopping the charger with a button or something before switching off at the mains?

Once a switch has performed a decent flash, there is often metal sprayed around the works, the contacts will be pitted, it will never be the same again and may have leakage due to the metal and compounds coating the internals.

Switching off a large current can put a lot of stress on a switch. But it should cope. I'd try fitting a new one, double pole and preferably a premium brand unless there are decor matching issues....

A Crabtree double-pole switched socket. (Crabtree are easier to wire than MK, despite MK’s claim about their push fit connectors). I would invest in a RCD adaptor for the charger as well.

Thanks all. Appreciate the help and Im thankful the RCB kicked in too!

Why would you do that?

The OP said the circuit in question is RCD protected.

Adding a second RCD is pointless because you have no control of which of the two RCD's will trip. It's not a case of the RCD nearest the load will trip, it's whichever reacts fastest. It adds no additional protection.

In this case where a relatively high current device is being connected to a socket you want to minimise the number of connections in the circuit. Suggesting a plug in RCD is just adding two more connections, two more opportunities for a high resistance connection which will generate heat and melt something.

The safest way to use a granny charger is to plug it directly in to a decent quality socket. Stopping the charge on the car is a good idea as it will remove the load on the socket switch when you turn it off.

I don't disagree, but the flip side is, break the circuit with a £15 plug in RCD, worst case, you lose £15 instead of calling out a sparky to change your socket.

This is a problem that should not happen, but I'm not knocked over by the surprise of it.

When you flipped the switch off, the contacts arced as the circuit was broken. The same could happen if you plugged a kettle in and flipped the switch mid boil, although less likely as it's a shorter duration of current flow so the contact would be cooler and less pliable.

Probably best to just replace the socket set with a new one for a tenner, after such a large arc crossing the switch contacts, they'll likely be degraded now.

If you unlock the car and remove the car plug ahead of breaking the circuit at the socket in future, that will avoid the same thing happening again.