Inverter UPS rcd

[Nalced]

Hi All,

wondering if anyone has some advice with inverters and rcd's.

I'm doing a van build soon and while a few places are having spring sales I've picked up a renogy 2000w inverter , setup a test bench with a consumer unit and tested the RCD functionality as I have done quite a bit of research regarding earth bonding and I wanted to test if the Renogy 2000w inverter has a floating earth. it does.

My plan is to connect the inverter to all mains sockets in the van, through a consumer unit with rcd, and then utilise the UPS functionality when EHU which will take over the earth neutral bond. When on battery the RCD does not trip ,as expected, because there is no earth. If I bond neutral and earth at the consumer unit everything works as expected. However i believe this setup will not work when EHU because I will have 2 bonds and potentially cause a bad accident .... from what I understand.

My question is what steps do others take to prevent this ? do you buy an inverter with rcd compatibility such as https://www.sunshinesolar.co.uk/Item/VP2500 or the very expensive victron? do you setup some sort of relay to disconnect the earth neutral bond when EHU ? if so does anyone have an example of how this would be achieved? or does it not matter when "off-grid"? 99% of the inverters out there are central tapped and there are lots of articles/videos out there of people just installing them in the van and off they go. am I thinking into this too much? do i need the RCD working when "off-grid" as the inverters built in protection is good enough or will the fact I'm not connecting one device but many sockets require a functional rcd as the inverter in-build protection will not work correctly with multiple devices?

help!

 

[Wombles]

Hi & welcome! Hopefully someone will be along to advise on this soon...

 

[autorouter]

My question is what steps do others take to prevent this ? do you buy an inverter with rcd compatibility such as https://www.sunshinesolar.co.uk/Item/VP2500 or the very expensive victron? do you setup some sort of relay to disconnect the earth neutral bond when EHU ? if so does anyone have an example of how this would be achieved?

The Victron Multiplus inverter/charger has an internal relay that disconnects the neutral/earth link automatically when the EHU is plugged in, so that there is only one earth path through the hookup post. When the EHU is disconnected the earth and neutral are connected as you describe.

 

[Lenny HB]

If you bond one side of the inverter output to earth and both output lines are switched via a changeover relay or contactor. When on EHU because the inverter outputs are isolated there will be no connection from neutral to earth.

The Victron Multiplus has the switched earth because it combines the inverter output and mains input to increase the avaliable power.

 

[DavidCh]

First, when the EHU is connected you have an RCD and your chassis and electrical sockets/appliances should be connected to the EHU earth (this will indeed be bonded to neutral much further back on the supply). When you connect your inverter to your sockets/appliances this earth MUST be disconnected.

Second, you can either.

a) Not connect an the earth. Since there is no neutral earth bond the inverter is ‘floating’ which means there should never be a path back to earth, and therefore no risk but then an RCD will not work.

or

b) Bond neutral/earth in the inverter and connect the earth to the appliances and chassis and fit an RCD. In this case this earth MUST be disconnected when the EHU is connected to remove your local neutral/earth bond.

It’s a call, floating should be ok but there is no RCD for protection which is ok since there is no neutral earth bond. RCD has protection but the earth has to be connected.


I used a relay which automatically switches all three (L/N/E) depending on if EHU is connected.

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