Yes, all working well. So far more than 600kWh of hot water delivered, saving well over £100. On a few occasions the HA add on was showing wrong info but HA reboot fixes it. The switch itself working perfectly. Here are some pictures
That’s great, Kamil, thank you. I’m assuming any oversized JB can be used. Is heat an issue at all with the Sonoff enclosed like this?
Thank you for your post Kamil, I have been exploring the idea of adding a Shelly EM plus a contactor to my 16A immersion heater to implement a similar intelligent solar diverter and off peak water heater however the Sonoff switch sounds interesting.
My DNO limited my solar PV installation to 3.68kW (16A) so similarly the cost of an Eddi made limited sense financially however I still prefer the idea of using my solar generation in whatever way makes most sense at the time, e.g. trigger kitchen appliance to start, heat water, and absolute worst case, export.
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@Valiante, I haven’t noticed any heat issues, although I haven’t been particularly thorough with checking. It was never hot on touch though as far as I can recall, probably because it is well oversized for the load. In addition, to reduce the ambient temperature in the cylinder cabinet, and to reduce heat loss, I used a lot of wool to wrap any hot water pipes or contact points around the cylinder - this made a massive difference! I can check in the next few days when I get a chance…
After the Sonoff was on for 2hrs, it was warm-ish on touch. Put a bath thermometer in the enclosure and that didn’t even reach 30C after 15min or so, with ambient temp of 21C. Hope that helps.
This is great information, thank you. Appreciate you taking the time to test that and update.
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@kamilb woudl you mind advising what the
‘sensor.solax_local_feedin_power’
Actually refers to on your inverter?
sensor.solax_local_feedin_power is how much is being fed back to the grid. So positive means surplus, negative means using the grid.
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I found a project on GitHub that is using Shelly 2.5 or Shelly EM as it’s using the same power meter to divert excess solar to the hot water.
@kamilb this is great, using the Sonoff powr3 is exactly what I’m looking to do with my immersion. Do you know if it is mounted before or after the switch?
Sonoff sits between the original manual wall switch and the immersion heater.
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great, thanks!
This looks perfect solution and something I’m looking to do.
In your tank, is your immersion heater just in the top? Or do you have an economy 7 style tank with 2 elements?
Just one large-ish tank, with one immersion heater located in the bottom half of the tank.
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great code @kamilb thanks for sharing it.
i have one question maybe you can help me out , i have a solar water heater with a TK-7 solar controller with bottom fixed sensor for non pressurized system , https://www.aliexpress.com/i/1005001734767504.html#nav-review and this is the water level water temperature sensor probe https://www.aliexpress.us/item/1005005332812635.html?gatewayAdapt=glo2usa , any idea what device i should use for the water temp and level sensor to integrate it into home assistant ?
No, sorry. Haven’t used additional sensors…
I do not have the solar panels, but do have control of hot water by both gas boiler central heating and by electric immersion heater.
I put a smart temperature sensor on the hot water cylinder, a smart switch on the electric immersion heater and another on the zone control valve for the hot water circuit. I then made Generic Thermostats for both hot water and immersion heater using the same temperature sensor. The idea is that heating is usually by the gas boiler, but the electric immersion heater acts as a top-up if the temperature falls below a certain threshold (e.g. after two people use the shower in quick succssion)
The thermostats are then scheduled by calendars using the blueprint Heating X2: Schedule Thermostats with Calendars
This might be interesting if you are interested in even more energy saving by adding extra sensors to the tank, and only boosting until you’ve got ‘enough’ hot water.
Also linked from there is my esphome based graphical tank display.
This is an interesting read. How do you measure when the water is not enough via the immersion, or just thinking does it have a thermostat control on it? I don’t have solar or anything, but just thinking about Octopus Agile and heating water overnight (need to consider if overnight electric is cheaper than gas), plus diverting other usage to overnight.
Hi @RogTP. Every immersion heater should have a thermostat to keep it safe. The max temp is typically set to 65C-70C. Now that gas is cheaper, there is less financial incentive to do so, but anything that doesn’t use gas is a win after all, even if costs are the same or slightly higher.