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Discussion Starter · #1 ·
A couple of months ago I bought a secondhand Rolec 7.2kw Type 1 tethered unit. It even had the original green RCBO, with no signs of burning contacts! It was cheap and looked simple enough to be durable. All was OK until about 2 weeks ago when I noticed it kept tripping said safety device. I bought a Garo equivalent to replace it after reading about the contacts overheating. This made no difference - the breaker trips as soon as my car takes current. I can only assume the little white module inside is faulty. Has anyone else had such an issue, and managed to return it to its former glory?
 

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The green RCBO will have been the newer replacement, as the original ones that burned out at the neutral terminal had blue printing. However, it sounds as if you may have a real earth leakage fault in the installation. Do you have the test results from the EIC? The installer will have done insulation testing, functional testing as well as testing things like Zs, so it's unlikely there was anything marginal when it was installed, but those values may give a clue.

Easy way to determine where the fault lies is to connect a vehicle simulator test box and do a few measurements. The installer will have done this, so I'd suggest getting them back to do some tests, it's a quick job to just plug the test box in and do a couple of quick tests.
 

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Does the contactor pull in?.. when you go to charge, do you hear a click?.. or does the rcd trip prior to this?
 

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The green RCBO will have been the newer replacement, as the original ones that burned out at the neutral terminal had blue printing. However, it sounds as if you may have a real earth leakage fault in the installation. Do you have the test results from the EIC? The installer will have done insulation testing, functional testing as well as testing things like Zs, so it's unlikely there was anything marginal when it was installed, but those values may give a clue.

Easy way to determine where the fault lies is to connect a vehicle simulator test box and do a few measurements. The installer will have done this, so I'd suggest getting them back to do some tests, it's a quick job to just plug the test box in and do a couple of quick tests.
Sounds like a DIY install Jeremy...
 

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Discussion Starter · #6 ·
Yep, it's a DIY job but it shouldn't necessarily be frowned upon - I consider myself experienced enough to do a decent job. It worked fine for 6 weeks, which made me think the installation was fine. Thanks for the pointers - I'll check the impedances.
 

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Yep, it's a DIY job but it shouldn't necessarily be frowned upon - I consider myself experienced enough to do a decent job. It worked fine for 6 weeks, which made me think the installation was fine. Thanks for the pointers - I'll check the impedances.
I wasnt frowning upon it, was just pointing it out that there isnt going to be an EIC/installer etc...

Does the contactor pull in and RCD trip, or does the RCD trip prior to the contactor pulling in..

fyi; the contactor will make more of a thud sound then a click...
 

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Discussion Starter · #8 ·
Yes, it trips when the contactor pulls in. The car charges fine on the Kia granny charger so I assume the car's not the issue.
 

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First things to check would be to isolate the supply and do the usual dead tests, but if the RCBO is only tripping after the car requests power, turning on the contactor, then the only way to test for a downstream fault is to simulate the car handshaking with the charge point. I found myself needing to do this a fair bit, and rather than buy a (rather expensive) vehicle simulator I made one:

146912


This makes testing a doddle, as the lead from the charge point can just be plugged in and the normal car signalling, as well as fault simulation, is then easy to do. With my MFT plugged in to the socket this makes testing the cable and connector easy, too. To fool the charge point into turning on only needs a couple of resistors and a switch, and although it's not ideal to poke probes up into the connector you could do this at a pinch, if you know what you're doing.

Another advantage of using some sort of test box arrangement is that you can make sure that it's an earth leakage trip and not an over-current trip. It may be that the car is trying to draw too much current, perhaps the charge point is advertising more than 32 A (possible with the earlier Rolec with the current setting resistor). Not something I've ever seen with a 32 A charge point, but it would be good to rule this out.

The fault isn't likely to be with the protocol controller I think, it's more likely to be in the cable or connector, perhaps with the CP, PP or current setting resistor connections, assuming that everything else checks out OK. Presumably this is wired as TT, if you're on a PME supply, so worth double checking that there's nothing awry there (shouldn't be, as the RCBO trip indicates there's a reasonable earth loop impedance, if it's tripping because of earth leakage).

I had a charge point trip a while ago just due to a build up of water inside the connector, after it had been left plugged into a car for a couple of weeks. The angle was such that water sat behind the terminals, rather than drain out through the hole on the underside, and there was enough dirt and water inside to give just enough leakage to trip the RCD. Might be worth having a quick look inside the connector to see if there's something similar.

Just for the legal bods, I will add that it's a criminal offence to DIY a charge point installation in England and Wales, without getting it inspected and tested for compliance with Part P, so the above is in no way intended to aid and abet such activity.
 

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Yes, it trips when the contactor pulls in. The car charges fine on the Kia granny charger so I assume the car's not the issue.
Ok, so you hear the thump?.. i was thinking of a faulty contactor... Usually they stick and then require too much current to pull in, tripping the rcbo... but if you clearly hear it, then maybe not that..

To check the contactor youd require the test instrument that Jeremy has suggested. Do not try to do this when the unit is under load...
 

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Discussion Starter · #12 ·
UPDATE: Sorry Robinson, I made a mistake when i replied before - it was tripping as soon as the RCBO was reset. Without specialist test equipment other than a multimeter, I could only test so much.

After granny-charging for the past few weeks, I done a lot of investigating over the past weaker so. I figured that the fault was still there after the swap for the Garo RCBO, so assumed the original Rolec charge controller was faulty. This was replaced with a shiny new Viridian unit, but the Garo RCBO tripped instantly each time. I began removing various wires one at a time. The contractor coil and EPC outputs made no difference. Removing the line or neutral from the EPC module enabled the RCBO to remain on, trip-free. There's never been any cable damage or water ingress so I wondered what there was left to change. I put the original Rolec (green, better than blue early ones?) RCBO back and it works fine!

It sounds remarkable, but I can only conclude that the original Rolec EPC developed fault to make the original RCBO trip. The Garo RCBO seemed faulty, so it tripped with the Viridian EPC - exactly how, I'm not sure. I've had my car on charge at about 7KW for 30 minutes without issue since. I'll keep everything crossed that there's no more charging drama to come.
 

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It is possible that there could be an earth leakage fault within the EPC. Not something that I've ever come across, but you never know with Rolec stuff! From what you've added it very definitely looks as if there's an earth leakage problem somewhere. If this is related to moisture (pretty common) then perhaps something's dried out, the insulation resistance has increased, and there's not enough leakage to get the RCBO to trip.

It would be a quick and relatively easy job to just do some insulation resistance testing and see if there's a problem, as even if the insulation resistance has now increased to the point where there's not enough leakage to cause the RCBO to trip, if there's an incipient problem somewhere that may well still show up as a lower than expected insulation resistance. Having said that, I've spent hours before now chasing around installations looking for the cause of a low insulation resistance, and it often isn't that obvious as to where the problem may be.

It can be a damned frustrating, especially where the fault only happens occasionally. Had one once where an intermittent trip turned out to be a combination of two things. Mice had damaged a cable that was completely hidden alongside the back of a chimney breast in a loft (tucked down behind a joist) and the flashing on the roof was faulty, so water could trickle down and sometimes reach the damaged cable. The frustrating bit was that it could take a day or more after it had rained for the water to make it's way into the damaged cable, and very often it could rain without there being a trip. I only found it when I decided that rewiring the whole of the duff leg made more sense that trying to find exactly where along it the problem was. Sod's law dictated that the damaged bit of cable was the very last bit I pulled out probably no more than a couple of feet from where it went in the top of the CU. . .
 
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