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WiFi MQTT Control Relay Thermostat + Demand Shaper Module

I’m new to home energy monitoring & just prior to buying my first EV a couple of months ago I purchased an emonTX connected to my house & EV circuits with a temp probe outside, logging to emonCMS running on a Pi that we had lying around.
I’m on the Octopus Agile tariff & I’d like to be able to control my immersion heater (rated at [email protected]/[email protected]) at the cheapest electricity rates, not specifically to save money because the gas boiler will almost always be the most cost effective method. There are a multitude of reasons; to be able to heat the DHW in summer without using the boiler and as an exercise in automation in preparation of a potential air/ground SHP as well as that it seems an interesting thing to do.

My question is, what is the simplest way to control the immersion heater, I have had a trawl around the site but cannot find the answer to:
Can I use the ‘WiFi MQTT Control Relay Thermostat’ and utilise the Demand Shaper Module?
Also could a 16A Sonoff or Shelly (MQTT controlled) wifi switch unit be used instead?

Or is the solution to go down the route, which I’d prefer not to do at present because not only do I not have the need for additional home automation but also due to a lack of time setting it up and the ongoing maintenance and inevitable diagnosing of issues later on.

Sorry no-one has replied to you yet. I haven’t got a clue - this is outside my area of expertise - but hopefully someone who knows will chip in.

Hello @MikeB and sorry for the slow reply. Yes you can use the WiFi Relay with the DemandShaper. You will need the EmonESP firmware installed on the WiFi Relay rather than the stock firmware for this to work.

I haven’t tried the 16A Sonoff, the EmonESP firmware does however work fine on the Sonoff S20 smart plugs so I imagine it should work ok if its basically the same ESP8266 based hardware inside.

It’s perhaps worth noting that the EmonESP firmware for the WiFi Relay does not yet take into account the temperature sensor measurement that you could use to measure the temperature of the tank and so the time to heat up. At the moment you would just need to set the relay to come on for a set time length every night, e.g 1-2h and the demandshaper will then select the best half hours to run.

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Thanks for confirming the use of the WiFi Relay with the DemandShaper.

As for the 16A Sonoff, I should have just Google’d this because now that I have it appears that it is common place to flash it’s ESP8266 with alternative firmware.

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