A means to switch off certain loads

Q&A and troubleshooting
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Hello all.

Background: my ESS installation consists of single-phase 5kVA MultiPlus-II, one 450|100 MPPT RS, 6.25kW Panels Half-Half E-W alignment & 16kWh DIY Battery. This is all managed by a Raspberry Pi-4 running Venus OS. It receives battery information from the battery via a Waveshare CAN-Hat but only for information. A smart shunt is the battery monitor and VM3P75CT is the grid meter.

Sometimes household loads exceed the 4kW limit of the inverter leading to undesired grid usage. I have a solar thermal water heater on the West roof that needs some ‘help’ from its in-built electric 1.5kW immersion heater. This is primarily used during ‘winter’ (cloudy) season at my near-equator location.

I am looking for a way to switch off the water heater when total loads approach/exceed tge inverter’s 4kW max, and then keep it off for a while(to be decided) when loads decrease beyond a threshold (to be decided). The ‘to be decided’ values should be adjustable.

So far, I’m leaning towards an implementation using Home Assistant and a Sonoff Smart Switch. However, I would like to hear of any more elegant solutions.

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You can use Shelly. Their relays go to 2400W, 16A at 240V. I used to use Node-Red to turn the heater on based on SOC, but now I just use a timer. There are a few ways to set it up. You can also do it all in the Shelly app if you add an energy meter by Shelly to measure the inverter power.

I have not used HA, and I dont know if Sonoff is local. Shelly works well locally on Node-Red.

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I have a similar setup. I use a switching relay and the programmable relay on the MP2 for this function. The MP2 relay can be programmed to switch when a certain AC load is reached. The auxiliary relay is then switched via an auxiliary circuit, which shuts off the load.

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Thanks @owenb79 @Sarowe1990. I’ll evaluate and let you know what works in a few weeks.