Author Topic: Powerjack 8000W LF Inverter Question  (Read 4913 times)

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Offline Pete

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Re: Powerjack 8000W LF Inverter Question
« Reply #30 on: August 03, 2016, 04:04:02 AM »
Hi Hacky, sorry I didn't get to see that post of yours until today. What you are describing sounds like what used to be called a "core balance relay".
I haven't had much to do with caravans other than to know that they have to have double pole switches and power points, that is to make sure that in the case of the lead connecting them to the mains is wired wrongly that both the active and neutral are switched off.
I run RDC's in my house and shed but I do have an earth rod and the Neutral of the inverter is earthed at the switchboards to make them work.
Older inverters would not allow the neutral to be earthed but all new complying ones do.
Also some of the older switch mode inverters also had a floating output that meant there was up to 110 volts on the neutral conductor. They were mongrels, I had an instance where a man was testing his batteries with a hydrometer and was getting small shocks off the batteries as it was raining at the time.
We fixed that by earthing the negative on the battery bank.
I will experiment  for you and get back. It may be possible to get an RCD to work by earthing the neutral at the inverter or switchboard and connecting the earth wire to the earth on the inverter. I will check it out and get back to you.

Offline Pete

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Re: Powerjack 8000W LF Inverter Question
« Reply #31 on: August 03, 2016, 08:21:06 PM »
Hello again Hacky, I tried out one of my inverters today in a stand alone situation. I connected an RCD to the output of the inverter. Then connected the earth wire to the incoming Neutral. Basically making a MEN (multiple earth neutral) system like we have in our houses.
The RCD performed fine.
So for your caravan I suggest that you try this.
Connect the inverter earth to the negative terminal of the battery.
Connect the neutral on the output side of the inverter to the Earth wire of the caravan wiring.
And see how it goes.
The inverter i used was a Chinese 1500 watt, high frequency job. All inverters built in the last decade or so should be able to run with the output neutral earthed.
I suggest that you get a multimeter or someone who has one and check that there is no voltage between the battery negative and the ground.
Just put the meter onto volts AC and put one probe into the earth, and one to the battery terminal.
Then try the same with the meter on volts DC just to check.
good luck
Pete

Offline Pete

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Re: Powerjack 8000W LF Inverter Question
« Reply #32 on: August 04, 2016, 04:41:56 AM »
Hello again Hacky, just in case my description is not easy to understand here is a diagram of how to connect the RCD up to get it to work.
Basically the Residual Current Device measures the current in the Active and the Neutral Conductor. If there is a difference then that means that current is leaking to Earth or through a person. When the Neutral is Earthed as I have shown in the diagram, if any current is flowing in the Earth wire it goes back to the inverter directly and there will be an imbalance in the current the RCD measures in the Active and Neutral conductor.
Some Inverters already have the Neutral and Earth connected on the back of their power points inside, It won't matter just connect as per the diagram and the RCD should work fine. To test the RCD just put a resistor or lamp between the active and earth  of one of your power points the RCD should trip.
Hope this helps
Pete