3 Pin Charger Tripping House

[goul]

I had inline RCD in extension cable when I tried - it didn't trip but the house did. Quick update - pod point install is fine and not seeing any issues.....but the 3 pin will still trip house even with everything else in fuse box switched off - it must be something leaking on the sockets, but I've not got to the bottom of it!

 

[MrBadger]

Yep. Same here. Tried new cable in different socket but still the same outcome. I'll go through each breaker one by one over the weekend to see if I can isolate what circuit it is on, or if it is the UMC. I had hoped to find a 3 pin public charger, but it was so dark I didn't see where the socket was. So even more in dark if its the UMC or not. Car seems OK with AC type 2 and DC super charging.

Not being able to charge at home is becoming a PITA. 25 mile round trip just to supercharge is putting more of a chill to the range than the temperature.

 

[arg]

I'll go through each breaker one by one over the weekend to see if I can isolate what circuit it is on,

A test worth trying, but beware that it doesn't guarantee to tell you what you think it tells you, because standard MCBs are only opening the L and the neutral remains connected.

So any neutral-earth faults in those circuits remain connected. Normally, (particularly if PME earth) the neutral-earth voltage is very small so these faults have no effect; however, as you draw more current - on any circuit - the L-N voltage increases and these faults start to pass current. Also, in this condition (L switched off at the breaker) the L and N are effectively in parallel, so sources of leakage normally attached to L are now attached to N (albeit driven by less voltage so having less effect).

So unless your breaker flipping immediately points a smoking gun, you really need to go round unplugging everything (or switching off any double-pole isolators there may be like the cooker switch). And if you have hard-wired things without a double-pole isolator (outlets with built-in USB chargers?) then you are still stuffed.

These RCD tripping problems are really hard to resolve without the right test equipment, and sometimes not easy even then.

 

[MrBadger]

So unless your breaker flipping immediately points a smoking gun, you really need to go round unplugging everything (or switching off any double-pole isolators there may be like the cooker switch). And if you have hard-wired things without a double-pole isolator (outlets with built-in USB chargers?) then you are still stuffed.

So if I turn off all MCBs on that side of the CU except that for garage circuit (its on its own circuit) then trying to start a charge, do I risk damaging anything if it does not immediately trip? What if I then start reintroducing different circuits back on? What if I get all on and car is still charging?

As I am still to get my wall connector sorted, I guess its probably best to wait until then as it sounds like even a sparkie with correct equipment may struggle to find root cause.

I will be specifying a separate CU in the garage (probably off the existing Henley block) with 40/20A MCB so I can have a 13A socket distinct from main house CU.

 

[booyaka76]

Not quite the same issues but the 3 pin charger keeps just stopping after like 5/10 minutes charging.

Nothing trips but it just stops - a pain in the arse whilst my Rolec is out of action (hopefully getting replaced on monday)

I constantly have to keep checking the app and restarting the charge again. Can't see what the issues is, tried extension cables, no cables, different sockets etc.

Public chargers are great - zero issues with various ones I've tried so far so can't be the car.

 

[arg]

So if I turn off all MCBs on that side of the CU except that for garage circuit (its on its own circuit) then trying to start a charge, do I risk damaging anything if it does not immediately trip? What if I then start reintroducing different circuits back on? What if I get all on and car is still charging?

No risk of damage, just risk of getting totally frustrated!

If you turn it all back on and it's still working, you have to conclude that it is a transitory effect as the car starts charging.

There's really three different factors that can cause this kind of apparently spurious tripping where no one device on its own causes the trip (all additive):

• Cumulative leakage. No one item is leaking enough to trip the RCD, but the sum of everything in the house adds up to more than the RCD's tripping threshold. Note that almost everything with electronics in it (including the car) will have a small amount of deliberate leakage: to suppress radio frequency emissions down the cable, small capacitors are placed L-E and N-E. Under normal conditions, the one N-E has almost no effect on leakage (because N and E are at the same voltage); the one L-E will have a constant, small, 50Hz current flowing through it. If all your leakage is down to these legitimate cases and it adds up to more than 15mA, then the only option is to split it into multiple circuits with separate RCDs (this is common with computer suites, exhibition stands etc). Added to this legitimate leakage is any fault leakage through things like failed insulation, damp getting into connections etc.
• N-E faults and "borrowed neutrals". There can be quite severe N-E faults (even N-E short circuit) which don't cause an immediate trip because N and E are close enough to the same voltage that no current flows across the fault. As you start drawing significant current anywhere in the house, N and E drift apart and suddenly the fault is passing current and the RCD trips. A relative of this is 'borrowed neutral' where a circuit has connected to the neutral of a different circuit (with a separate or no RCD) so there's no leakage to earth but the current returns down the other neutral and the first RCD sees an imbalance. Another sneaky one in this category is if there's a high-resistance N-E fault but the on/off switch has been put in the neutral rather than the L (or it's a double-pole switch and the L opens first) - when everything is turned on and working normally, the fault is N-E and so not passing much current; open the switch and suddenly it's in effect L-E (plus the resistance of the load) and so passes much bigger current. Ceramic cooker elements (notorious for getting leaky when damp) sometimes show this effect where the RCD trips as you switch it off. One theory I had looking at the reports in this thread is that maybe the new UMC (which has a two-pole contactor in it) happens to close L first and then N: this will, for the short time the contactor is in motion, give you double the car's normal leakage (because both the L and N suppression capacitors are live).
• High frequency effects. RCDs are primarily specified for pure 50Hz AC. Various kinds of short-term transients or high frequency interference can cause them to behave outside spec - acting either more or less sensitive than they should be. Induction hobs are one notorious source of high frequency emissions; Renault Zoe EVs are another. You can buy special RCDs with improved immunity to these problems, but often people end up changing the RCD for another one that happens to be a different model and say "oh, the old RCD was faulty!" when in fact it wasn't faulty but sensitive to transients or HF.

So the preferred way of debugging if you have the equipment is first to do an insulation test with everything unplugged (to eliminate wiring faults), then to use a clamp meter with a sensitive mA range around L and N at the supply to see what the standing leakage is before you add the car. If the standing leakage is close to the RCD rating (15mA for a nominal 30mA RCD) then you go around turning things off to find where it's coming from.

 

[MrBadger]

We made a little progress this afternoon running through different combinations of circuits then sockets.

The good news is that we can charge, but its a PITA as we can only do this when we turn off a couple of devices in the kitchen to start the charge. I can't remember exactly what permutations definitely works as we got to the stage after a while that us, the car and the circuit board had had enough repeat tripping for the day.

We have a separate fridge/freezer and a small freezer and it would appear that if either of these are plugged in and on when charge starts, the RCD will trip. Can't remember if the plugging in bit is important or whether its just sufficient to be switched off, nor can I remember if the rest of the house was plugged in when we managed to get the charge to start, but all eyes are on these two devices. They are Leibherr so decent make but the fridge freezer is connected to 3 pin via factory fitted euro/uk adaptor, so I will cut that off and fit an MK plug. The freezer has a moulded 3 pin uk plug, however, during a recent episode of nasty transient power cuts, the freezer has not been the same since. Its currently off as its complaining audibly of power failure and I cannot seem to be able to reset.

So progress but no solution.