OKI (Metcal) MX-5000 off grid?

[andrew96]

does anyone know how to make the  (the one with the lcd display) work off grid? It just shows GND FAULT, but there is a good ground connection! works fine on grid. The older MX-500p-21 I borrowed to test works just perfect. Is my only option to downgrade to a older model? or has someone cracked being able to use these off grid?
many thanks
Andrew

[thm_w]

MX500 is also supposed to have the same functionality.
I assume its just testing if Neutral and Ground pins are connected, is your neutral floating?

https://www.eevblog.com/forum/reviews/what-metcal/msg340565/#msg340565

[andrew96]

Ah thankyou, Yes the neutral will be floating for sure, Being off grid its a inverter, just like in that post you kindly linked to which says using a isolation transformer it won't work! I wonder if anyone has worked out how it monitors and manage to trick the unit into working. hopefully someone has a idea on how.

[thm_w]

Floating neutral is unsafe and you should not be setup like that in the first place.

Google: neutral bonding off-grid

[andrew96]

Yeah I have worked out how I can do it!! I cannot bond the neutral of the inverter output to ground, Inverters really don't like that! I read that a lot when searching the net!

BUT!!! my inverter CAN switch to grid power (if connected) when the solar is not available and the batteries have been exhausted, the Inverter IS earth bonded, to the earth terminal but doesn't have grid input, so I can just link the neutral input which would normally be connected to the grid to the earth terminal so it is PME bonded at the expected grid input terminals. this works perfectly when I tried it this morning!!  If I ever connect grid to the inverter I just remove the link!!!!

This way as thm_w says it will be safe! I had no idea on this floating neutral issue until using the Metcal, there is nothing about it in the inverters manual about that at all!! it just says the inverter can be used on or off grid with no further information!! so everything now works as if it was grid based power and safe!!

Happy with that outcome!!!!
Many thanks to everyone that took the time to read this post, and reply