I have two multiplus 48/5000 for an off grid cabin. I want to wire them in parallel and only enable the slave unit when the master unit is close to being overloaded in order to reduce the idle power consumption.
I was thinking to connect a relay output on the master unit to an input on the slave unit. Then program the master output to close the relay when the output power goes above a certain threshold, and program the slave input as a safety switch to disable the output.
There are a few undocumented but very effective techniques you can use to expand your system’s capabilities.
First, you can use the generator virtual switch to automatically power on a second inverter when the load or input power remains high for a set time. In this setup, the master unit stays configured normally, and the slave is simply a standard inverter acting as a power source. The slave’s output is connected to the AC In of the master. It is not specially configured it just supplies AC power like any other generator would. You can use the remote on/off switch on the slave to control when it powers up, triggered by the generator virtual switch on the master.
Additionally, you can use the ESS Assistant on AC Out to allow the slave to synchronise with the master and help service the loads. I have a setup like this using two small 1200VA units in a shed, connected to the AC Out of a 5000VA inverter. An energy meter in the consumer unit measures load and coordinates supply for both the AC Out and grid-tied loads in the house. Setting this up took some time, including some Node-RED automation and research, but the system now operates extremely well.
I’m not entirely sure what would be needed to make this work in a fully off-grid scenario, but it should be achievable. One thing to keep in mind is that the potential delay when using the remote on/off control, together with the generator start signal synchronisation, may not be instant. Still, it would be a very interesting project to develop further.
Thanks for you detailed response. Seems that parallel operation is not the way to go here, but that serial connection should provide the same capabilities. Looking forward to test this out