earthing an inverter

[vintagescubaman]

well my partial re wire is imho well, but i just wanted to check something, i have a victron inverter which has an earth point on its chassis. Now this may sound like a silly question but is this for earthing the 230v side, i assume it is, in which case i would want to use mains earth cable to an earthing point on the hull. I also have another query, my consumer unit does not appear to have a dedicated earth for the radial circuits. I have a unit with built im switch that can be used to swap between inverter, generator and shoreline, it has live, neutral and earth for all the inputs but only two live outputs, one 6 amp and the other 16 amp and a single shared neurual out? Am i missing something? Thanks for any advice!

[Arnot]

well my partial re wire is imho well, but i just wanted to check something, i have a victron inverter which has an earth point on its chassis. Now this may sound like a silly question but is this for earthing the 230v side, i assume it is, in which case i would want to use mains earth cable to an earthing point on the hull. I also have another query, my consumer unit does not appear to have a dedicated earth for the radial circuits. I have a unit with built im switch that can be used to swap between inverter, generator and shoreline, it has live, neutral and earth for all the inputs but only two live outputs, one 6 amp and the other 16 amp and a single shared neurual out? Am i missing something? Thanks for any advice!

What Victron inverter are you installing? This may have an impact on how you wire the earths...

 

Regards

 

Arnot

[vintagescubaman]

ah that is a good point, its a phoenix 3000, not a combi inverter charges

[Arnot]

well my partial re wire is imho well, but i just wanted to check something, i have a victron inverter which has an earth point on its chassis. Now this may sound like a silly question but is this for earthing the 230v side, i assume it is, in which case i would want to use mains earth cable to an earthing point on the hull. I also have another query, my consumer unit does not appear to have a dedicated earth for the radial circuits. I have a unit with built im switch that can be used to swap between inverter, generator and shoreline, it has live, neutral and earth for all the inputs but only two live outputs, one 6 amp and the other 16 amp and a single shared neurual out? Am i missing something? Thanks for any advice!

Given that the inverter is just that and not a combi, then the earth stud on the casing should be connected to the main hull earth point. This is the single point where the DC systems are also bonded to the hull. The cable size should idealy be one up (4mm) on the power conductor side (2.5mm).

 

Your consumer unit probably has all the earth connected together internally, probably to a series of linked connections but this can easily be checked with a meter. All the earths on the outgoing cables should be connected to this. There should also be a 4mm bond between the consumer unit and the main hull earth point.

 

The shared neutrals on the outputs, whilst not ideal, is quite common and providing the whole installation is protected by an RCD (which it certainly should) it is going to be safe in this respect.

 

Consumer units with two outputs are designed with the anticipation of a ring main for the power outlets connected to the 16A outlet and an immersion heater connected to the 6A outlet. You may well find that it is difficult to connect more than two radials (plus the immersion heater feed) to this type of unit.

 

It doesn't make it clear in the installation or user instructions for this unit if the neutral output is connected to the protective earth internally although in some of the installation diagrams on the Victron website metion this. The neutral should be bonded to the protective earth at the output of the inverter if it isn't done internally.

 

Regards

 

Arnot

[Giggetty]

Given that the inverter is just that and not a combi, then the earth stud on the casing should be connected to the main hull earth point. This is the single point where the DC systems are also bonded to the hull. The cable size should idealy be one up (4mm) on the power conductor side (2.5mm).

 

Your consumer unit probably has all the earth connected together internally, probably to a series of linked connections but this can easily be checked with a meter. All the earths on the outgoing cables should be connected to this. There should also be a 4mm bond between the consumer unit and the main hull earth point.

 

The shared neutrals on the outputs, whilst not ideal, is quite common and providing the whole installation is protected by an RCD (which it certainly should) it is going to be safe in this respect.

 

Consumer units with two outputs are designed with the anticipation of a ring main for the power outlets connected to the 16A outlet and an immersion heater connected to the 6A outlet. You may well find that it is difficult to connect more than two radials (plus the immersion heater feed) to this type of unit.

 

It doesn't make it clear in the installation or user instructions for this unit if the neutral output is connected to the protective earth internally although in some of the installation diagrams on the Victron website metion this. The neutral should be bonded to the protective earth at the output of the inverter if it isn't done internally.

 

Regards

 

Arnot

 

If I bond my (Chinese) inverter neutral to earth, the inverter signals fault and refuses to output. Explanations, anybody?

Edited July 24, 2010 by Giggetty

[larkshall]

If I bond my (Chinese) inverter neutral to earth, the inverter signals fault and refuses to output. Explanations, anybody?

 

(chinese), thats your answer

[rjasmith]

If I bond my (Chinese) inverter neutral to earth, the inverter signals fault and refuses to output. Explanations, anybody?

 

 

It may have a "centre tapped output" ie the output is really 120v - 0v - 120v instead of 0 - 240v. The case is perhaps already earthed but is internally connected to the 0v common rail. If you then earth what you believe to be the "neutral" (which is actually one of the 120v outputs) as well, you will then have shorted out part of the inverter's output and this is what it won't like!

 

Not easy to explain in words perhaps but I hope it helps!

 

Richard

[Mat B]

If I bond my (Chinese) inverter neutral to earth, the inverter signals fault and refuses to output. Explanations, anybody?

 

On some cheap inverters the earth stud is connected to a centre point in the circuitry. this means that the blue and brown wires are each at 115V with respect to earth.

 

(In other words both blue and brown are "Hot", a bit like the American system)

 

If you bond the blue wire to the earth stud you are shorting out half of the output.

 

Connecting the earth stud to metal work but not bonding to blue will ensure that the RCD trips if somebody gets a shock from either hot wire.

 

m@

 

Edit RJA beat me to it.

Edited July 24, 2010 by Mat B

[vintagescubaman]

ah thats excellent, as i thought the earth on the inverter is dc, however i notice that my consumer unit doesnt have an earth bond, its one of the midland service centre units. Could it be the case that the 230v earth bond to hull should be run from one of the 3 earth points provided for power input, as thex are all linked internally i would think that this would be acceptable. Thanks for the on going advice, its much appreciated!

[rgreg]

Given that the inverter is just that and not a combi, then the earth stud on the casing should be connected to the main hull earth point. This is the single point where the DC systems are also bonded to the hull. The cable size should idealy be one up (4mm) on the power conductor side (2.5mm).

Your consumer unit probably has all the earth connected together internally, probably to a series of linked connections but this can easily be checked with a meter. All the earths on the outgoing cables should be connected to this. There should also be a 4mm bond between the consumer unit and the main hull earth point.

 

The shared neutrals on the outputs, whilst not ideal, is quite common and providing the whole installation is protected by an RCD (which it certainly should) it is going to be safe in this respect.

 

Consumer units with two outputs are designed with the anticipation of a ring main for the power outlets connected to the 16A outlet and an immersion heater connected to the 6A outlet. You may well find that it is difficult to connect more than two radials (plus the immersion heater feed) to this type of unit.

 

It doesn't make it clear in the installation or user instructions for this unit if the neutral output is connected to the protective earth internally although in some of the installation diagrams on the Victron website metion this. The neutral should be bonded to the protective earth at the output of the inverter if it isn't done internally.

 

Regards

 

Arnot

 

I was told by an installer "most people don't bother with this". Risky or not?

[WotEver]

I was told by an installer "most people don't bother with this". Risky or not?

Yes: http://www.smartgauge.co.uk/earthing.html

 

And for more reading: http://www.smartgauge.co.uk/nb_ac_sys.html

 

Tony

[Arnot]

I was told by an installer "most people don't bother with this". Risky or not?

I have to say that if it isn't bothered with it probably wouldn't matter too much. The risk is negligible.

 

If the casing was mounted to the steelwork of the hull then this would do it anyway. If it is mounted to a non conductive surface, the earth does two things; it provides a protective earth for anyone working on the inverter when it is disconnected from the distribution should they need to do so or if the consumer unit develops an earth fault and it provides part of the interference supppression system.

 

For what it costs and the time it takes, you may as well just do it.

 

Arnot

[rgreg]

Yes: http://www.smartgauge.co.uk/earthing.html

 

And for more reading: http://www.smartgauge.co.uk/nb_ac_sys.html

 

Tony

 

Hmm. Bit of a concern if the installer's statement that "most people don't bother" (referring to earthing an inverter case) is true.