Will connecting mains to Inverter act only as a backup?

[GeoffR]

I'm a solar -off-grid newbie, and a technician set up our off-grid in our shed, but he's now become unreachable. I have a simple question.

Installed is a SUMRY HMS 3K-24V, and it has a 240v plug to allow it to be connected to mains if needed. If I leave this connected, will the unit still operate effectively as a battery system?

The reason being, that I have a water tank pump that trips the inverter when it starts (due to a momentary current surge), but when the mains power is connected it handles it OK. I'm wondering the system is just getting what it needs momentarily from the mains, and then reverts back to battery power, or if the entire system is now running off mains, and the batteries are superfluous.

My daughter also wants to use the batteries to help operate a small kiln throughout the day, hoping the batteries can charge sufficiently when in use. All is fine when connected to 240v of course, but are we getting value from the batteries?

Sorry if my question is too basic, but I'm not sure how to find out. The inverter configuration instructions are difficult to follow.

thanks,
Geoff

 

[sunshine_eggo]

It depends on how it's configured.

It could be behaving as you suspect, or it's drawing from grid and passing through to loads.

Do you have a manual you can link?

 

[Mattb4]

Are you observing it during operation? Almost all of these AIO's have a display with a depiction of Grid, PV, inverter/charger, battery and load. Lines connecting between these things indicate how it operates.

You Sumry may or may not be able to do grid assist. It may also be able to export. Consult your Manual.

ETA: Another though comes to mind. If you have insufficient battery with a grid connection than heavy loads will cause voltage sag and a low voltage transfer to utility. Once load is started the demand drops and battery voltage rises back up.