DIY - Am I testing my EV charger RCBO correctly?

[stefan9107]

Hi all, just a quick one to ask about an issue I'm having with my EV charger. I'll give a little background first but ultimately I want to know if I reached the correct conclusion or whether I'm actually doing something wrong with the testing?

I had an EV charger installed a couple months back but didn't have my car yet to test it. Car arrived just before Christmas, plugged in for my first charge and it just stopped working after about 20 minutes. The charger didn't go into any of the normal fault modes that would be expected, it just lost power altogether. I went and checked the breaker and all appeared fine. I waited for it all to come back online which took several hours and then tried again. This time it failed after less than 5 minutes. Since then I've had varying success with the longest charge lasting just over 30 minutes, but normally it dies after just 5 or so.

Now the weird thing is I've had to start flipping the RCBO off and then back on to get it to work. Not quick flicks but off for 15 minutes and then back on. This doesn't always work though and I'll flip it off for 30 minutes or an hour and then back on. Eventually it always comes back on (until now anyway). I hadn't used the charger in a couple days because of the issue and was reading around about what might be the fault. Someone suggested trying the test button on the RCBO. I hit the test button and the breaker went. All good. Well since then I haven't been able to power my charger back on and the test button no longer works.

I figured I'd get the multimeter out and see if anything obvious was going on. I put the meter on the live input to the RCBO (A on picture below) and I'm reading 240V. But when I put it on the live output (B below) I'm getting nothing (used the same earth point both times). Now I know testing voltage can sometimes be a bit of an odd one so I was wondering if there is anything downstream that could affect my results? Or with the RCBO in the on position, should I be getting 240V at point B and therefore something is clearly wrong?

On a side note, I also found it odd that the RCBO is rated to 32A when that's the max rating of the charger. Shouldn't some redundancy be built in using say a 40A RCBO?

Thanks for any help ahead of time - it's much appreciated.

 

[westward10]

If you are testing to earth you should get mains voltage between A/earth and B/earth with the rcbo switched on.

 

[stefan9107]

Okay thanks. Looks like its no good then.

 

[westward10]

Could be just a loose connection which has now become permanent. The fact it worked for short periods especially after you switched the rcbo on and off which could have disturbed the connection. Get the people who installed it back.

 

[stefan9107]

Could be just a loose connection which has now become permanent. The fact it worked for short periods especially after you switched the rcbo on and off which could have disturbed the connection. Get the people who installed it back.

Fair point. It didn't look like anything was loose and I gave it a quick tickle with the screwdriver and it felt tight. Either way though, I've got them coming back after the bank holiday to take a look.

Thanks for your help.

 

[stefan9107]

Could be just a loose connection which has now become permanent. The fact it worked for short periods especially after you switched the rcbo on and off which could have disturbed the connection. Get the people who installed it back.

Okay so here is something that I'm confused by.

When I last switched the RCBO back to the on position several hours ago, I measured the output one last time and it was 0V. Okay, it doesn't work I thought. Then just now I notice that my charger has power to it as the lights are on. I go back to the output of the RCBO and now its reading 240V. I haven't touched it in that time frame. So what can possibly of changed in those few hours that suddenly makes the output go from 0V to 240V?

This is why I thought something on the charger end could possibly make it so that at the point even with power able to travel through the RCBO, I could somehow be seeing 0V at that point B. In an ideal world I'd like to disconnect the charger to rule out it somehow interfering. But that might just be my lack of understanding.

 

[westward10]

The issue is not the charger however the load from the charger may well be indirectly causing the issue to occur. From what you describe this sounds like a poor connection and I would personally be leaving the rcbo switched off until someone can look at it.

 

[stefan9107]

The issue is not the charger however the load from the charger may well be indirectly causing the issue to occur. From what you describe this sounds like a poor connection and I would personally be leaving the rcbo switched off until someone can look at it.

Okay will do. Got the electrician coming out Tuesday morning to investigate so will leave it until then. Thanks again.

 

[westward10]

Let us know the outcome.

 

[brianmoooore]

I'll have a fiver on the source MCB terminal cage being tightened up without the busbar being in it.

 

[stefan9107]

It was a faulty RCBO. Not sure of the exact specifics but the electrician managed to replicate the fault I had, replaced the RCBO and all is now working.

Thanks for your help.

 

[El Kid]

I have the same SPD-RCBO unit that you have and mine came with a Busbar that connected up all 4 output terminals (x2 Live and x2 Neutral) at the bottom of the units.
Looks like yours has been setup without any busbars and with just ferrules connecting up the cables.
Will you be able to post a picture of your setup showing the bottom(underside) of the wiring. thanks