Invertor earthing

[tcox]

My 230v system consists of a ring main, with an RCD and the earth bonded to the hull by a large steel bolt, which is purely for use with a shoreline.

 

However, with no access to shoreline, I am planning to put in an invertor (cheap 800w modified sine job), using the already provided 3 pin plug changeover system.

 

This presumably means that the output of the invertor is earthed, however, there is a further wing-nut for earthing on the invertor itself. Should I connect a wire from this to the bolt into the hull?

 

Many thanks in advance!

[Guest TerryL]

My 230v system consists of a ring main, with an RCD and the earth bonded to the hull by a large steel bolt, which is purely for use with a shoreline.

 

However, with no access to shoreline, I am planning to put in an invertor (cheap 800w modified sine job), using the already provided 3 pin plug changeover system.

 

This presumably means that the output of the invertor is earthed, however, there is a further wing-nut for earthing on the invertor itself. Should I connect a wire from this to the bolt into the hull?

 

Many thanks in advance!

 

The inverter case and the neutral should be earthed to the hull for the RCD and some appliances to work. Some inverters have a centre tapped earth so check it can be used with neutral/earth or altered to disconnect the centre tapping earth.

[RobinJ]

My 230v system consists of a ring main, with an RCD and the earth bonded to the hull by a large steel bolt, which is purely for use with a shoreline.

 

However, with no access to shoreline, I am planning to put in an invertor (cheap 800w modified sine job), using the already provided 3 pin plug changeover system.

 

This presumably means that the output of the invertor is earthed, however, there is a further wing-nut for earthing on the invertor itself. Should I connect a wire from this to the bolt into the hull?

Ideally you need some protection on the 12V supply (big fuses/isolator) and the case should be connected to the 12V earth point which is usually the same as the 240V one. If you have a galvanic isolator fitted and use the plug swapping technique, it may mean the inverter is connected to the shoreline side.

 

If you can find one of those test plugs with the three neon/leds on, it is worth checking the connections of any inverter you get. As many are wired as centre tap for the European market, they are often wired up wrongly. You could have a look yourself, but if in doubt get an electrician to check it.

 

The earth pin on the 240V outlet is usually (but not always) connected to the case, this also needs strapping to the neutral to ensure the RCD works, however you often find when you do this there is a Live-Earth fault, as the Live and Neutral are connected to the wrong pins (with centre tap it doesn't matter). It is worth having an RCD trip test done, as this not only tests whether the RCD will work becuase of the wiring, but will also check the speed of your RCD (<20ms). The test button on the RCD provides an internal function test and does not guarantee it will trip under fault conditions.

[tcox]

Many thanks for fab answers

 

Have gone and got inverter today. It is neutral earth. However, it did not have a wing-nut for earthing the case as I was expecting. Does this mean that I don't need to bother with earthing the case, or should I try to solder a wire onto the case somewhere?

 

Also got a 100A fuse and holder for the 12v side.

[stuart]

Many thanks for fab answers

 

Have gone and got inverter today. It is neutral earth. However, it did not have a wing-nut for earthing the case as I was expecting. Does this mean that I don't need to bother with earthing the case, or should I try to solder a wire onto the case somewhere?

 

Also got a 100A fuse and holder for the 12v side.

 

 

See if the earth pin on the output of the inverter is actually connected to the case (use a continuity test on a multimeter). If its connected, dont worry. Otherwise it might be worth connecting the case to -ve/earth. I doubt you'd solder to the case though - probably best drilling a hole and screw/bolt in a ring crimp connector.

[Guest TerryL]

Many thanks for fab answers

 

Have gone and got inverter today. It is neutral earth. However, it did not have a wing-nut for earthing the case as I was expecting. Does this mean that I don't need to bother with earthing the case, or should I try to solder a wire onto the case somewhere?

 

Also got a 100A fuse and holder for the 12v side.

 

Check to see if the earth pin is connected to the casing, if so you can earth the system to the hull before the RCD (if not already done) possibly at the plug but the inverter will only be properly earthed to the hull whilst the plug is in, so if you can fit another earth at the inverter socket or casing it may be better but it really depends on the risk and location.