Hi
I've got a really awkward problem. My house has a dual supply - mains electric (PME) and Solar PV. When the Solar Inverter is on, the RCD trips. The Solar is feeding to a MCB that is sharing an RCD with house electrical circuits. One of these circuits has the caravan plugged into an ordinary 3 pin socket in the garage via commando converters. If I turn the caravan off, the RCD does not trip. I've then narrowed it down to the caravan's electrical sockets by turning off the other circuits in the caravan. I've unplugged everything but I have no access to unplugging the microwave or the battery charger so they are suspect devices.
In summary, the 30mA RCD only trips when BOTH the caravan's electrical circuits are on AND the solar PV supply is on.
I've scoured the net and electrical forums and some suggestions include using a 100mA RCD for the solar and also not sharing the RCD with other consumer unit circuits, but electrician friends tell me that it's quite normal to use 30mA and to share the RCD with other consumer unit circuits. Help and advice would be much appreciated.
Try unplugging the mains EHU lead from the caravan. Try unplugging the EHU lead from the commando convertor.
Try switching off the main switch in the caravan.Try switching off the MCBs in the caravan. You probably have a 10Amp and a 6Amp
You're trying to remove items from the circuit until it holds in and identify the bit you plug in which causes the trip. Somewhere the live or the neutral is shorting to earth.
Could be a cross connection in the commando convertor or EHU.
Could be the microwave or charger, they are both items which can trip RCDs.
Might not be anything to do with the caravan... That's what I was thinking... Very easy to substitute some other simple load like a 100w lamp in the garage socket.
Firstly regarding the garage socket - I've just plugged in a 150W lamp and no problem. As I say, it doesn't matter which socket the caravan is plugged into - same problem.
Regarding Navver's suggestions, I have already done most of these. Commando converter on its own - no problem. EHU lead through commando converter - no problem. EHU lead connected to caravan and main caravan breaker switch turned off - no problem. Lighting circuit 6Amp MCB on - no problem. Heating circuit 10Amp MCB on - no problem. Water heater 10Amp MCB on - no problem. Electrical sockets 10Amp MCB on - this is where it goes wrong. - also tried using different EHU and different EHU converter - same problem.
It's definitely something on that 10Amp MCB (labelled sockets) in the caravan that's doing it. Problem is that I can't find a way of isolating the microwave and battery charger.
In summary - I don't get why it only does it when the solar is on and not at other times. Also, I'd be interested in knowing if this has happened to somebody else because Elddis have never come across this before. I also can't get the warranty repairers to test it on my driveway so they will have no way of seeing the problem (apart from the video I did - but when they test it at their site it probably won't cause any problems because of the combination of the solar (from house not caravan).
Most earthed appliances will have a degree of earth leakage. Microwaves do as they have 'noise' suppression devices to filter interference form affecting other appliances. I'm not sure what PVs have, but they will have complex electronics to convert the output to 230V AC and I guess noise filters.
The problem that I suspect that you have is that the sum of the earth leakage is more than 30mA. Which is why the 'electricians' suggest replacing the RCD with a 100mA one. In my opinion it would be better to split what is connected to the existing 30mA RCD across two. So putting the caravan on one and the PV on another.
------------- Ollie
2016
Monplaisir - Provence
Camping Les Gorges du Loup
I personally wouldn't like to change the RCD to a 100mA. You are already outside the PME zone of protection and the PME earth bonded to the caravan body & chassis. The 30mA RCD is important to protect you. Add to that you have a potentially faulty piece of kit in the caravan; changing the RCD will add to the risk by downgrading a safety device.
Most electronic kit has switch mode power supplies with a functional earth leakage. With computers we try not to put more than 8 on one 30mA RCD because of nuisance tripping. It may be you just have too much so splitting it across 2 RCDs may help.
Oliver - thank you - I think you are absolutely right. In the pub last night my friend who is an electrician and I came to the joint conclusion that it must be combined earth leakage - your post has helped confirm this.
Today I put a commando inlet socket on the exterior of the house and ran a cable to a separate 30mA RCD which is actually for the electric car charger but is now shared between that and the caravan commando socket. To my delight, there is no more nuisance tripping so it must be a combined earth leakage problem.
Navver's comment about 8 computers reminded me of my teaching days when we used to get all sorts of nuisance tripping when first turning on a classroom of computers - after many electrician visits and all sorts of suggestions, the conclusion was to split the circuits into no more than 8 computers per circuit.
I hope this thread is of use to somebody some day and saves the hours of investigations I've had to suffer. Thank you to everybody who has contributed.
Key words: solar pv caravan commando electric nuisance tripping rcd mcb earth leakage