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An odd one: at the in-laws and the granny charger trips their electrics. Immediately. Tried 3 different sockets and put charger on 6A setting. Tested the charger elsewhere and it works. But also the same sockets run a kettle fine, which must be a similar or greater draw than 6A granny? So, any ideas on what could be wrong or what to do to diagnose? TIA.
 

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An odd one: at the in-laws and the granny charger trips their electrics. Immediately. Tried 3 different sockets and put charger on 6A setting. Tested the charger elsewhere and it works. But also the same sockets run a kettle fine, which must be a similar or greater draw than 6A granny? So, any ideas on what could be wrong or what to do to diagnose? TIA.
What's it tripping, an RCD or MCB, or RCBO?

Excess current will trip MCBs, load imbalance/earth leakage will trip RCDs. RCBOs do both in one unit.

If they've got type A RCDs then it could be DC leakage that's causing a trip that won't trip type AC RCDs which might make it work elsewhere.

Regardless if it's been tried on some different circuits, it's probably faulty if other appliances are working fine.
 

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Discussion Starter · #3 ·
What's it tripping, an RCD or MCB, or RCBO?

Excess current will trip MCBs, load imbalance/earth leakage will trip RCDs. RCBOs do both in one unit.

If they've got type A RCDs then it could be DC leakage that's causing a trip that won't trip type AC RCDs which might make it work elsewhere.

Regardless if it's been tried on some different circuits, it's probably faulty if other appliances are working fine.
It’s the main switch that is tripping - see pic - not any individual breakers. Is there any way to test the charger itself?

It’s not a big deal for me - the charger belongs to the loan car I’m using so it’s not mine - right now it just means spending £20 at a rapid instead of charging it at the in-laws!

Thanks for your help.

 

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I guess it is tripping the RCD rather than the MCB so the Granny with car connected is causing an earth leak big enough to cause a trip.

Several possible causes:

1) There is already a lot of leakage from fish tanks, ovens, USB chargers, etc. that a teeny bit more is pushing the RCD over the 30mA limit.

2) The MCB is overly sensitive.

3) There is a fault in the granny/car that is causing a legitimate trip and the other RCDs are faulty.

This is an inherent problem in having loads of circuits on the same RCD. Many years ago RCBOs (breakers with both overcurrent and earth leakage protection built into a single device) were too expensive so either the whole house was put on one or the house was split int two with half the circuits on one RCD and half on the other. Nowadays RCBOs are cheap enough that there is only need for separate RCDs if you are exercising extraordinary economic restraint.
 

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It could be a poor earth elsewhere and the granny is just pushing it over the edge and causing the issue.
 
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RCD on the incomer says TT supply to me.
It's not unusual for a normal household to have something like 20-30mA of earth leakage due to all the power electronics we have - LED lightbulbs, PCs, TVs etc, so plugging the car in probably provides enough leakage under normal operation to take it over the edge.
Not much can be done without changing the RCD, I suspect, which will end up being a fuse board change - not a cheap job
 

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This is an inherent problem in having loads of circuits on the same RCD. Many years ago RCBOs (breakers with both overcurrent and earth leakage protection built into a single device) were too expensive so either the whole house was put on one or the house was split int two with half the circuits on one RCD and half on the other. Nowadays RCBOs are cheap enough that there is only need for separate RCDs if you are exercising extraordinary economic restraint.
But still likely to find older installs that have a separate RCD. Or worse yet that have no RCD protection at all.
 
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