Difficult question, I know, lots of variables. In the UK, we have a Harrington 6kVA generator to back up our solar installation with our Multiplus inverter/charger. When the generator starts, the gen circuit breaker trips when the Multiplus tries to accept gen power. Has anybody experience with these generators? We previously used Hyundai gen with no problem.
The problem was caused by the N and E being linked at the fusebox.
Thanks for reporting back. I hope everything is sorted and working smoothly now.
Does it have a 30mA rcd trip? You could swap this out for a 100mA trip or even just a main switch
@jacko Yes, it has a 30 mA RCD trip. That's what trips. not the MCB, sorry I wasn't more precise. Do I infer from what you say that this behaviour is to be expected? What do you mean by a main switch? There is a switch which can disconnect the gen output.
@WKirby Not sure about the N-E link. When you say '... present and correct' do you mean that it should be there? And if it should be there, and the ground protect relay is active as @jacko suggests, then how do we solve the problem. Is it possible, and safe to do, to de-activate the ground protect relay in the inverter?
Some background. The RCD is designed to protect AC system problems such as floating neutrals and the absence of a neutral to earth bond in an AC system. An AC system should have only ONE neutral/earth bond active at any time.
Your Multiplus "assumes" that any external AC source(grid or generator) you have will provide its own neutral/earth bond. When the Multiplus detects an AC source it does the following:
Turns off the inverter function
Opens the neutral/earth bond transfer switch
Closes the AC input transfer switch
I suspect your generator does not have neutral/earth bonded. It's an easy fix. The generator RCD senses no bond so it trips.
Pat
I dont think the RCD in the generator would detect if there was a N-E link in place behind it, its ever looking for a current flowing on the earth which there wouldnt be if there was no link, or a difference in current flowing out on the live to whats returning on the neutal, i think it will be this as the inverter kicks in it causes a difference in current its quite common with inverters, you could overcome it with an RCD with a highter trip current or if thats not enough swap for a main switch which is just a two pole switch. It would then be worth taking a ze reading to check you have a good earth reading. If you dont its probably been designed to have an earth stake and operate as a TT system. If you do have to take the RCD out you would obvioulsy add RCD protection on the output of the inverter, in the fuse board usually.
Thanks for those comments. The wiring diagram of my Harrington HRD060 generator suggests to me that the N of the 230V output is connected to the frame (via the RCD), and we have connected the frame to a copper earth rod. So, @Pat Davitt, we have a neutral/earth bond, correct?
I have been advised (by a Victron installer) to uncheck the 'Ground relay' checkbox on the Inverter page in VEConfigure. I am guessing that when this relay is unchecked it will prevent the system having two ground points (one at the generator, one at the Victron) and thus prevent the RCD tripping. Is this correct thinking? Would welcome enlightenment.
It's good the generator has the neutral/earth bond. However, you should leave the "Ground Relay" box checked. If you don't, you will have no neutral/earth bond when running on Inverter power. The Multiplus has a sequential operation when switching between inverting and an external power source that prevents both bonds from being active at the same time.
Are you sure there is not a hardwired neutral/earth bond somewhere in your internal wiring?
Pat
Sorry, just saw @jacko answer ('Good point if there’s a N-E link in the generator and the ground protect relay is active in the inverter before it accepts the input it would trip') which I missed earlier. That seems to confirm the advice I have been given.
You could try it but don’t think it will make a difference the neutral and frame are connected so kinda like tncs earthing arrangement when the generator is running, if you uncheck the ground protect relay it will not operate any different you’ll just have a worse earth reading as you will be relying on the earth stake at the generator as your main earth wether the generator is running or not you will not get as good an earth reading in inverter mode as when the inverter makes its own N-E link with the ground protect relay. Prob best to try it and see if you already have the stake in. If it still fails you’ll need to change the rcd or use a main switch and rcd protection on the output side
Understood, thanks. We are starting the gen automatically from a CCGX so can't rely on manual switching (which is what I infer from your 'main switch'?). Our gen and Victron earths currently each have their own earth stake, about 15 metres apart; our installer advises that gen earth is attached to the Victron earth stake.
Hi William,
First the disclaimer, this is work that has the potential to be fatal and should be undertaken by a suitably qualified and experienced installer.
I wrote an explanation of my observations of various systems in a previous community post. Please have a read here:
Guy,
Thanks for bringing us all down to "earth". Sometimes we forget, that if you don't know exactly what you are doing, this stuff can kill you, or cause a fire.
Thanks,
Pat
@william i couldnt write many characters to reply above
Sorry no thats not what i meant, so you can have an RCD main switch which is a residual current device so looks for differences in current flowing in the live and neutral often due to earth leakage which isolates both the live and neutral (2 poles) or you can have a main switch which is the same shape but without the RCD functionality its just is a 2 pole isolator if you google 100 amp main switch youll see what i mean. When i set these up i always leave the ground protect relay on as standard but if its causing problems from earth leakage and tripping at the generator you can ever use a 100ma RCD main switch so it looks for a difference of 100mA or more before tripping (but still gives you RCD protection and is alowed on distribution circuits in the UK) or go to a main switch, if you have to do this you need to have an RCD at the fuseboard, there should also be an overcurrent device on the generator like an MCB that stops you overloading the generator or trips under dead short. technically you dont need the earth stakes at ever as they are both TNCS devices so your ever connected to the generator and using its N-E link or the inverter and using its N-E link both will give you very good earth fault loop impedance readings, thats my take on it but others may have stuff to add
That’s ok, you would need the stakes if you had set up sub mains with tt earthing arangements, that’s the recommended practice for separate out buildings in the uk, as you have the stakes in place you can leave them in they’ll do no harm, under fault conditions the fault path goes through the ground back to the stake from the tt sub main boards
Try physically disconnecting all AC outputs from the multi too see if it still has the issue. It may be something more downstream of the multi that's causing it.
