I am looking at an ESS system with Multiplus 2 GX 48/3000, auxiliary inverter, and a 14.3kwh battery.
The normal household loads are usually within the 3kW of the MP2GX. However, having a teen that likes long (7.2kW) showers, to maximise the usage of the battery and maximise ROI, I’d like to support that. This can only stay within G98 if the auxiliary inverter can never export to the grid.
My proposed system uses an automatic power transfer switch. The 5kW aux inverter is connected to port A (the priority source), while the grid is connected to port B. The ATS guarantees no short between A and B, so the 5kW inverter won’t affect the G98 rating.
In normal operation, the aux inverter will be off. The Multiplus 2 GX will be connected to the main consumer unit via AC-IN only. It will charge during Economy 7 hours, and operate in PowerAssist mode outside these hours, sharing the normal daytime loads, but with a current sensor on the main feed, to prevent grid export.
When the shower is powered up, I hope to be able to detect the load (e.g. AC-OUT > 3kW), and use an assistant plug-in to enable the relay output when [(outside E7 hours) AND (AC-OUT > 3kW) AND (SOC > SOC(min)) ]
The relay will then power up the 5kW inverter. The ATS (transfer switch) will detect power on its priority port, connect the 5kW to MP2 AC-IN, and disconnect the grid. With the MP2 in Power Assist mode, there should be 8kW of inverter power to support the shower load.
When the shower is powered down, the inverter will shut off, and the system will revert to a grid-tied G98 load-sharing system.
I ruled out parallel operation, because it would require G99. Similarly, chaining a Multiplus 2 GX or Quattro to the MP2 output in PowerAssist mode would also require G99.
In addition to a few questions, I’d appreciate an expert sanity check, and any recommendations.
With the demo software, it doesn’t seem possible to play with an ESS plug-in for a MP2GX, so it is not clear if the MP2GX is able to sense currents independently on AC-IN, AC-OUT1 and AC-OUT2. It’s important that I can sense the load on AC-OUT1 independently. Or, is there an alternative in-line AC load sensor that could sit on AC-OUT1 and would play nice with the relay assistant?
Hopefully, the JPEG system diagrams will help clarify what I want to do.
Many thanks
Jools
