I have a grid-connected site I am helping out with.
It is an on-grid single phase site with two Multi's in parallel, a DC MPPT with solar attached, and all site loads on the AC output.
It is running ESS and set to use the inverter/charger as the grid metering point in the ESS menu.
The strange behaviour we see is this: If we start the system up with no loads connected to the AC output, the Multi throws up a (false/incorrect) "Grid Lost" alert (and does not use grid energy) instead of properly connecting to the grid.
As soon as we apply loads to the AC output, the (false) "Grid Lost" alert disappears and the unit starts to interact properly with the grid.
I can't explain why it should do this - we are not changing the grid connection in any way.
We have tried removing ESS - no change to this behaviour. We tried just one Multi instead of 2 in parallel - no change. We tried changing grid codes in the unit (normally set to AS4777:2015) - no change.
In all cases the unit throws up a 'grid lost' alert when the grid is in just fine (and refuses to use the grid), until we connect the house loads. When we connect the loads, then the Multi starts to use the grid and stops throwing up false 'grid lost' errors.
The Multis are running the latest Multi firmware (510, 29 Feb 2024).
Voltage is seen on the grid input at all times (see screen shot below). It just doesn't get used until there are loads on AC out.
It seems very strange.
