TWC - Charge interrupted due to circuit tripping

[stonecoldrmw]

Hi all,

I'm curious to note if anyone else has experienced issues with the TWC tripping out.

So on 2 occasions, I've had my car on scheduled charge overnight to make the best use of the cheap tariffs (Octopus Agile, it's done wonders for my electricity bills even with an EV - dm me for referral). When I came downstairs the following morning and checked the app, I had a notification saying charging interrupted. When I checked the unit, the light was off and I had to check the circuit only to find that the circuit had tripped.

The installation was done by a Tesla recommended installer but as I posted a while ago, I wasn't 100% confident with the 3 guys that installed it.

Before I ring them up and ask for it to be looked at, I just wanted to see if others have experienced this too and what your remedies have been.

 

[AnthonyLR]

Nope, mine is fine. Sounds like your instincts with the 3 guys were correct

 

[Plagued]

My brother had an issue when his TWC started tripping the MCB after a couple of years. He assumed it was a faulty MCB and bought a replacement to have fitted. Turns out that when the electrician moved the consumer unit earlier that year he'd not fully tightened up the bus bar so it was touching but not tight. Things like that can be really dangerous and can end up with wires and connections overheating.
I'd get a sparky in to check everything is tight.
I am assuming here that they fitted the correct cable and MCB in the first place

 

[Dilly]

Call them back. Shouldn’t happen if it hasn’t been installed for very long. One of my Zappi’s has been there for 3 years, the other for two years. Both without issue. Both can use 7 Kwh simultaneously.

 

[Roy W.]

I’ve had a TWC for about a year, installed in my garage. In that time it has never tripped, and I’ve never reset it. You’re right to be suspicious of the installation!

 

[MrBadger]

This occurred with 2020.16.2.1 and I have had 2/3 spurious charge errors - never had a failed charge with that setup up until that point so bit of a coincidence. Second defo tripped the RCD, not sure about the first - I didn't see the TWC green light (it was very bright conditions so easy to miss) and I instinctively pressed the RCD reset but I don't think it actually needed resetting and something else had happened as I subsequently needed to power off/on that circuit to clear the fault. It happened on second charge after .16 update too. That definitely tripped the RCD at very end of charge. Third charge was fine. Jury out on whether it will blow next time - I've moved on a couple pf updates since then. A few other people noted charge issues around the same firmware. Its almost as if a fault condition occurred right at end of charge.

 

[Adopado]

Call them back. Shouldn’t happen if it hasn’t been installed for very long. One of my Zappi’s has been there for 3 years, the other for two years. Both without issue. Both can use 7 Kwh simultaneously.

Charge points do have their failures from time to time ... even Zappis ... I'll not catalogue my own Zappi issues unless you really want me to but suffice to say they can have their issues too!

 

[Plagued]

The firmware update may cause charging issues but it should never trip a breaker, the charger itself should never draw more than 32A (on single phase) and no combination of car or cable should alter that.
MCB's are rated at a set temperature, they will either trip if the current exceeds the rating of the MCB at their designated temperature, or if the temperature of the MCB is increased dramatically by a poor connection or other failure. A 40A MCB would get tripped by a 32A current if it was over say 60 degrees C.
So you could have a faulty charger drawing too much current, an incorrectly rated install using the wrong size cable and MCB (unlikely), a faulty MCB or a mistake when fitting by not correctly securing the cables on either the charger or consumer unit end.
Ultimately it should never trip, so something's wrong and it shouldn't be the car. Get someone to pop round and take a look.

 

[MrBadger]

RCD tripping is different to MCB tripping. Much easier to trip a RCD and conceivably, a change to the charger characteristics from a firmware update could I believe trigger a change in electrical behaviour whilst it was transitioning between modes - like at end of a charge when mine tripped.

 

[Jonslatt]

I have had this happen with my original Chargemaster charger. Will routinely trip if I plug cable into car, starts to wind up to charge but then I cancel on the app.

 

[Plagued]

RCD tripping is different to MCB tripping. Much easier to trip a RCD and conceivably, a change to the charger characteristics from a firmware update could I believe trigger a change in electrical behaviour whilst it was transitioning between modes - like at end of a charge when mine tripped.

Ahh I was assuming when he said the "circuit had tripped" he was referring to the whole circuit from the MCB, but you could be right, maybe he means the RCD, only stonecoldrmw knows the real truth. The truth is out there!

 

[stonecoldrmw]

Ahh I was assuming when he said the "circuit had tripped" he was referring to the whole circuit from the MCB, but you could be right, maybe he means the RCD, only stonecoldrmw knows the real truth. The truth is out there!

Yes, the it's on the local EV charge board (if that is such a thing!) that tripped. The rest of the electrics are fine. I'm not the best with electrics hence why I rely on a professional sparky but deffo think I'll be calling them back to check it over.

 

[MrBadger]

Yes, the it's on the local EV charge board (if that is such a thing!) that tripped.

Did it have a test push button with something like test monthly written on it, or just a single flip switch with maybe B32 or B40 written on it?

 

[ACarneiro]

I’ve had a TWC for about a year, installed in my garage. In that time it has never tripped, and I’ve never reset it. You’re right to be suspicious of the installation!

Same here.
Two TWCs for about a year. I think I did have to reset one of them once when some read lights came on but that was the only thing. Hasn't happened again.
I'd suspect a dodgy install as well...

 

[pow216]

Well I found the car at 25% this morning and the C32 MCB tripped. First time this has happened in 9 months. The breaker is in its own consumer unit and I charge 00:30 to 04:30, two things likely to keep temperatures low.

 

[Plagued]

My reference to temperatures wasn't really about it being hot weather, more a poor contact with the terminals of the MCB. if things aren't correctly tightened up then a smaller contact patch can over heat to the point of setting things on fire/badly burning cables and melting plastic. The issue my brother had was the poor contact with the bus bar was causing the MCB contacts to heat up and presumably get to over 60 degrees in winter before tripping. If it hadn't tripped it would have probably continued to heat up until it burned out. an MCB with a heat issue will generally trip after some time rather than right at the start. If something trips instantly there's a more fundamental issue.

 

[stonecoldrmw]

So update on this...

Yes I know I originally raised this thread back in June, I've had some things to deal with! Anyway, since then, the TWC has tripped a few more times with the latest being last week. So this morning I finally got round to emailing the company that did my install. Got a call back around an hour or so later asking if they could come round today to review and investigate.

Chap came and checked all connections and set up, etc and couldn't find any fault. So next step is he will email a contact at Tesla for a little more investigation before I get in to it with them as he says, there could be a fault with the unit.

 

[LukeUK]

What's the device that's tripping? Post up a photo, it will be a great help.

Charging at 32A on a 32A MCB is not ideal. If you look at the characteristic curve of an MCB, you don't have much change in current between running indefinitely, and running for some period of time, which could be measured in minutes or hours, before tripping. MCBs are built to a tolerance as well, they're not perfect devices.

The MCB is ultimately providing protection for the cable, so if a 32A MCB is fitted it raises the question of what size cable is fitted.

 

[stonecoldrmw]

What's the device that's tripping? Post up a photo, it will be a great help.

Charging at 32A on a 32A MCB is not ideal. If you look at the characteristic curve of an MCB, you don't have much change in current between running indefinitely, and running for some period of time, which could be measured in minutes or hours, before tripping. MCBs are built to a tolerance as well, they're not perfect devices.

The MCB is ultimately providing protection for the cable, so if a 32A MCB is fitted it raises the question of what size cable is fitted.

Will post a pic later but let me just say, the majority of what you just said went straight over my head!