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Adding earth and RCD to two pin inverter
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motorhomer:
Hello all, I need some help to clear up a question which was asked about two pin inverters and adding an earth

If I have an inverter 12v to 240v which only supplies a positive and neutral output, how would someone add an earth to the output so they can install a RCD.

I was thinking like industry installation the earth will be connected to the neutral at the output end next to the inverter and then an RCD will be fitted live and neutral further down. I cant see any reason this would not work.

Would it make any problem grounding this earth to a vehicle chassis with the 12v negative also grounded to the vehicle chassis
BrokenYugo:
A RCD/GFCI doesn't need an earth connection to function, they work by checking for a current imbalance between live and neutral, doesn't matter if the leak is to earth or elsewhere. In fact in the USA where we often build them into the socket it's permitted to install one in an old 2 wire installation with no earth connection, works great.
Zero999:


--- Quote from: BrokenYugo on August 08, 2021, 05:04:33 pm ---A RCD/GFCI doesn't need an earth connection to function, they work by checking for a current imbalance between live and neutral, doesn't matter if the leak is to earth or elsewhere. In fact in the USA where we often build them into the socket it's permitted to install one in an old 2 wire installation with no earth connection, works great.

--- End quote ---
That's not true. An RCD or GFCI does need the mains to be earthed to work. It will work for appliances which aren't earthed, but it definitely requires a connection between the neural of the mains to ground.

--- Quote from: motorhomer on August 08, 2021, 04:36:41 pm ---Hello all, I need some help to clear up a question which was asked about two pin inverters and adding an earth

If I have an inverter 12v to 240v which only supplies a positive and neutral output, how would someone add an earth to the output so they can install a RCD.

I was thinking like industry installation the earth will be connected to the neutral at the output end next to the inverter and then an RCD will be fitted live and neutral further down. I cant see any reason this would not work.

Would it make any problem grounding this earth to a vehicle chassis with the 12v negative also grounded to the vehicle chassis

--- End quote ---
The neutral should be connected to the chassis, in order for the RCD to work. The problem is the inverter will most likely consist of a DC:DC converter, with an H-bridge on the output to convert it to AC. The problem is, the DC:DC converter might not be isolated, in which case, you need an RCD which will work with DC.
David Hess:

--- Quote from: Zero999 on August 08, 2021, 05:21:42 pm ---
--- Quote from: BrokenYugo on August 08, 2021, 05:04:33 pm ---A RCD/GFCI doesn't need an earth connection to function, they work by checking for a current imbalance between live and neutral, doesn't matter if the leak is to earth or elsewhere. In fact in the USA where we often build them into the socket it's permitted to install one in an old 2 wire installation with no earth connection, works great.
--- End quote ---

That's not true. An RCD or GFCI does need the mains to be earthed to work. It will work for appliances which aren't earthed, but it definitely requires a connection between the neural of the mains to ground.
--- End quote ---

It needs a conductive path between the mains and earth for a failure to occur to be detected, which means that it works fine without it because then there is no possible failure.  An imbalance between the hot and neutral currents means that there is a third path, which could be through earth ground or not, and that is what the RCD or GFCI detects.

If you had an RCD or GFCI installed after an isolation transformer, then it would detect a simultaneous ground fault and failure of the isolation transformer.  Some isolation systems monitor the voltage across the isolation transformer to detect failure so they can disconnect when conditions become hazardous.
motorhomer:
Ok so I understand how the RCD works. With out an earth the only way it will trip is a leak from positive back to UK inverter without going through the RCD. So back to neutral side. With the earth it's more likely to go back this route and trip quicker

So my theory is ok to connect the earth to neutral at the inverter output and then the RCD

Not sure about any issues connecting this earth to chassis found some info where it's adviced to do this.
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