Invertor in a van earthing.

[flyingsparks]

Fitting an invertor in a van where a couple of sockets will be wired in the back, should the earth of the ac side be connected to the vehicle chassis? I am in debate with someone about this!! What do you think?

 

[securespark]

Does the inverter provide an "earth"?

If so, where from?

And how would you connect it to the vehicle?

See this forum: http://www.dutchforce.com/~eforum/index.php?s=005316b9fecb3e0bf5c0aa29308c4727&showtopic=34075

 

[flyingsparks]

As far as I am aware the invertor in question does not supply an earth. Only the 2 connections to the dc side. I assume then the live side is obviously isolated to true earth and so earthing the van chassis is not a good idea. The tyres are obviously isolating the van chassis from true earth anyway.

 

[ericmark]

I would bond the metalwork to the inverter the one I fitted had a terminal for this where the output if for multi items but would not bother with a single output in same way as no bonding for a shaver socket single output.

 

[plugwash]

IMO yes. If you don't do it and there is a fault between the mains wiring and the metal of the van it may resykt in dangerous voltages remaining on the van's bodywork.

 

[RF Lighting]

It doesn't matter if the van comes 'live' as there's nothing to reference the live to. It's an isolated supply.

 

[flyingsparks]

It doesn't matter if the van comes 'live' as there's nothing to reference the live to. It's an isolated supply.

That's my thoughts exactly. So really it shouldn't matter being earthed or not?

 

[ban-all-sheds]

Can't be earthed.


Unless you get out and drive a rod into the ground, I suppose.

 

[plugwash]

It doesn't matter if the van comes 'live' as there's nothing to reference the live to. It's an isolated supply.

It matters a lot if the metal case of the appliance plugged into one of your sockets becomes connected to one side of your inverters output and the body of your van becomes connected to the other side of your inverter's output.

 

[RF Lighting]

That requires two faults. If you're earthing the van, all you can do is derive the earth from the supply neutral, which would mean you only require one one fault for a potential to exist between a faulty appliance and the van.

 

[JohnW2]

That requires two faults. If you're earthing the van, all you can do is derive the earth from the supply neutral, which would mean you only require one one fault for a potential to exist between a faulty appliance and the van.

What if there were an RCD on the output of the inverter, with the van body (and CPC for sockets/appliances) connected directly to the inverter's 'N' output (upstream of the RCD)?

Kind Regards, John

 

[ericmark]

Is the inverter output TN or IT? If it is a TN output i.e. one line wire is bonded to the body and designated as neutral and there are more than one socket outlet then clearly it needs bonding.

If however it's an IT supply then the rules become more complex. To connect either line supply to the chassis of the vehicle could increase rather than decrease the risk so it would need bonding through a sufficiently high impedance.

I have only worked on IT system once and it was a nightmare but we would have to decide what a sufficiently high impedance is? If we consider using a 30ma RCD then the impedance will need to be 50/0.030 = 1666 ohms so it would seem connecting a 1k5 resistor between van body and line before the RCD would be enough to ensure the RCD would operated but would not turn it into a TN system.

A Residual current monitoring devices (RCMs) has this resistor in the device so it may be better to just have a warning lamp and use a RCM as done with IT control systems?

I think if we consider the risk then the problem arises that items only used in the van could develop faults on different phases since it is unlikely that two items will develop the faults at the same time to have a warning that faults have developed is enough. So I would think the RCM route is likely best method!

 

[securespark]

Unless you get out and drive a rod into the ground, I suppose.

Surely you wouldn't get out to drive the rod into the ground?

 

[ericmark]

Unless you get out and drive a rod into the ground, I suppose.

Surely you wouldn't get out to drive the rod into the ground?

I think we all use the word "Earth" when we mean "Bond" and since we assume the tools are used inside the van it would only require to be bonded however if we are using the van as a power supply for remote tools than yes we may need to drive in an earth electrode. However the problem would arise when one wants to test this electrode as one would have to also install another two electrodes to test it against.

So back to risk assessment and the risk of two or more tools being used from the van both having faults on different phases is really very small so I would not really think the risk warrants installing earth electrodes.

 

[EFLImpudence]

I think we all use the word "Earth" when we mean "Bond"

...........

.............