Earthed appliances and inverters

[caddy]

I have heard that it is not safe to run earthed appliances from an inverter, is that correct?

 

[tonyidle]

Anything that relies on a safety earth (in other words anything that isn't double insulated) will lose that protection when connected to an inverter. Earthing one side of the output of the inverter creates a neutral and restores protection.

 

[caddy]

Anything that relies on a safety earth (in other words anything that isn't double insulated) will lose that protection when connected to an inverter. Earthing one side of the output of the inverter creates a neutral and restores protection.

Does that mean that any appliance with a metal casing and an earth could be dangerous unless the inverter is earthed?

 

[Raul]

I have heard that it is not safe to run earthed appliances from an inverter, is that correct?

Not quite, the appliance will be protected by a rcd, so it needs a inverter that’s rcd compatible. Professional inverters are compatible with rcd.
Even on mains if the appliance developed a fault leak to the metal casing and no rcd, you will get zapped. You need a rcd in conjunction with earth bonding to offer protection.

 

[tonyidle]

Does that mean that any appliance with a metal casing and an earth could be dangerous unless the inverter is earthed?

Not necessarily. Dangerous in terms of you touching something and receiving a shock - unlikely. But a fault in the appliance might not blow a fuse or trip the RCD until next used on EHU.

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[Revolvor]

I am about to install a

Victron Phoenix Pure Sine Wave Inverter - 12V 500VA (VE.Direct-enabled)​

in my MH.

I have searched and read most of the posts on the forum regarding the need (or not) to have an RCD in the circuit, but is still not clear to me. A lot of the posts relate to situations where sockets can be powered by the inverter or EHU - or both

I noted Raul 's post about removing the cover and making changes to link the earth and neutral in order to enable use of an RCD.

I've also read some posts by autorouter

The installation will be independent of any other 230v circuits in the MH, and will just power one or two sockets.

My questions are:

1 Should I install an RCD?
2 Can it be an "in-line" type or should it be a "house" type, in an enclosure?
3 Should I utilise the earth lug on the Inverter?
4 If so, what should it be connected to? (Vehicle Chassis?)

Thank you.

 

[Revolvor]

Is anyone able to give me any help with this?

 

[Raul]

My opinion, for a 500va inverter keep it simple and isolated to the rest of electrics, its double isolated and a rcd will not help you without a N PE bonding. If your inverter manual documents snd provides a bonding option, then its possible to be done inside on the pcb spade connector.
If not, forget about the bonding, and use it with suitable over current protection, fuses/ breakers.

 

[treblid]

I don't understand why you would want to introduce an 'earth' when an inverter effectively provides an isolated output. In other words, the output has no reference to true earth and therefore can not provide a shock from extraneous metalwork in a fault condition to true earth.

Over current protection should of course still be provided.

 

[LithiumConvert]

The earth in of the sockets should be connected to an earting point on the inverter which in turn should be connected to the EHU earth connection.

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[treblid]

The earth in of the sockets should be connected to an earting point on the inverter which in turn should be connected to the EHU earth connection.

I can agree with this if you assume the inverter earthing point has no reference to its output; i.e. the output winding is still isolated.

If you strap one side of the output connection to the inverter earth point and/or the EHU earth connection, you have introduced an unnecessary reference to an artificial 'earth' which increases any likely shock hazard.

 

[Revolvor]

My opinion, for a 500va inverter keep it simple and isolated to the rest of electrics, its double isolated and a rcd will not help you without a N PE bonding. If your inverter manual documents snd provides a bonding option, then its possible to be done inside on the pcb spade connector.
If not, forget about the bonding, and use it with suitable over current protection, fuses/ breakers.

Thank you. It will be isolated from the rest of the 230v system. I have details of the spade connector to be moved to bond earth to neutral. I will just connect an RCD and MCBs.

 

[Revolvor]

I don't understand why you would want to introduce an 'earth' when an inverter effectively provides an isolated output. In other words, the output has no reference to true earth and therefore can not provide a shock from extraneous metalwork in a fault condition to true earth.

Over current protection should of course still be provided.

Thank you. I wasn't sure either, which is why I asked the question.

 

[Revolvor]

The earth in of the sockets should be connected to an earting point on the inverter which in turn should be connected to the EHU earth connection.

Thank you. The system will be totally independent of the EHU circuits.

 

[Revolvor]

I can agree with this if you assume the inverter earthing point has no reference to its output; i.e. the output winding is still isolated.

If you strap one side of the output connection to the inverter earth point and/or the EHU earth connection, you have introduced an unnecessary reference to an artificial 'earth' which increases any likely shock hazard.

Thank you. From what I've read in this and other posts, I will not be connecting the earth point to anything.

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[VXman]

The earth in of the sockets should be connected to an earthing point on the inverter which in turn should be connected to the EHU earth connection.

If you are not using EHU (which is most likely if you are using an inverter) then the earth will not be going anywhere anyway???

 

[Raul]

If you are not using EHU (which is most likely if you are using an inverter) then the earth will not be going anywhere anyway???

It does if it’s bonded to neutral, it goes back to source as it suppose to. Adding a third conductor, PE, provides a safe path back to source for the fault current, ( floating earth).
But, it can not be used with ehu earth in the same circuit, it has to be separated when ehu is present, usually ehu provides its own earth and as its a different source.

 

[IRHP]

The earth in of the sockets should be connected to an earting point on the inverter which in turn should be connected to the EHU earth connection.

If you have ehu why would you use an inverter?

 

[Revolvor]

If you have ehu why would you use an inverter?

If you have something like a Victron Multiplus II and you are on an EHU that has limited capacity - say 10amp or 6amp, the inverter can cut in to share the load if you need more capacity.