question

Hi @paullindsay

I prefer to do this using node red and some shelly smart switches. Node red will allow you more options when it comes to defining the turning on criteria of the water heater conditions. I believe you can achieve this using victron assistants but they tend to be less flexible.

Assuming you have normal water heater (either on or off and not one with variable power consumption/PWM control). ,

Then you'd essentially make node red turn on water heater by activating the shelly smart switch when you hit absorption phase and have excess power. (i do this use http node in node red but you can use mqtt or even websockets on the newer shelly smart switches).

If there isnt sufficient power and you start using battery you turn off water heater.

You have to becareful with criteria to make sure water heater isnt constantly being turned on and off. ie you need a buffer between on criteria and off criteria but this is easy to do in practice.

In terms of controlling 240v or gas and makiing sure both aren't on at once. It will depend how you intend to control the gas side. I would recommend a smart switch or smart heating system with a local api. That way you can check the status of the gas side of heater before turning on 240v side.

Again you could use a shelly smart switch. And add logic to node red that does .

if(shellyGas !== on && excessSolar){

msg.payload = 1;

return msg; //this will then flow into http node that activates the shelly240 that turns on 240v water heater

}

Node red means you can get really specific with your criteria so like you said checking if shore power is connected you could add an extra element to if statement like

(if acInVoltage !== 0) //ie no shore power

I'm happy to help with custom node red code if you can provide specific criteria.