Hmm. An immersion heater is on its own circuit, so what’s the actual worst that could happen? Always on, always off, intermittently working, wouldn’t something in between that leaks current trip the circuit breaker in the consumer unit?
Does the potential for “welding shut” happen every time the unit draws power when previously it was “off”, regardless of whether it’s because the sonoff came on or the thermostat turned the immersion heater on?
Wouldn’t that be what you would design for if you are producing a 16A switch - 0 to 16A repeatedly?
The potential for welding shut happens every time the load is switched. Open or closed. When will it happen? There are no rules. I have had contactors weld shut (on large cranes) in a couple of weeks. I’ve had some which have worked for years and years without fault.
Will it happen to your sonoff? You don’t know. My caution is that Sonoff (brilliant devices that they are) make the very very cheap. They would still make them to spec and withing safety but it’s the cheapest of all the items that is used.
Over cautious? Yes, it’s your (my) house and for the extra beer-token I know I can rest easy. Simple as that. It could be years before something happens. It could be weeks.
Will the mcb catch it if it welds shut? No, it’ll not know anything is wrong.
Out of interest, I have a POW which I just want to use for measurement and will be removing the relay. Before I do this I will switch a spare heater (c.3KW) on and off every 30 seconds as part of a community test
Cool, I’ll be interested to see the results - the other item I’m controlling with a POW R2 is a heat storage range oven, which switches from 0kW to 2kW very frequently, so it’s probably more susceptible to this than the immersion heater.
Can you show me how you would wire up the other kit to be controlled with the Sonoff?
I don’t have a raspberry pi, but for my use I suspect the firmware the Sonoff comes with will be okay… So why do you flash the firmware, is it so you can universally control/program a range of different switches/devices? Or is there some other advantage…?
The stock firmware connects to a server owned by Sonoff on the public internet and sends all the data there, you have to create an account with them and use the company’s app to control the switch.
I’m not sure if the Sonoff will work with openhab without replacing the firmware - as far as I can tell, you have two choices:
a) go the fully proprietary route with all the privacy implications, e.g. use the Sonoff with its default firmware along with something like nest or Alexa
b) go the fully open source route with sonoff-tasmota and openhab
Personally, giving control of things inside my house/network to a company based in China is an absolute no-no, so I didn’t even connect the Sonoff to the internet until I had replaced the firmware with sonoff-tasmota (which is open source and doesn’t send any data outside your network).
I don’t even turn them on and configure them from new. Flash them right out the box.
Personally I use https://github.com/xoseperez/espurna
It’s great software with loads of features but I just use it for mqtt and stability (personally, it has too many features crammed into it).
regarding the relay option - I’ll blame too much wine (I’m on holiday in the Italian countryside )
Using a second relay you’ll not be able to measure the current without a modification to the sonoff itself.
If you wanted to stay with your current setup, at least monitor and chuck a warning if the relay should be off but there is current draw. That would be a good safety check.
I’ll still get the setup and trigger the heater load continuously to test it for curiosity reasons but I suspect your arger is hammering it quite well and will be the same test. Add the safety check for good measure.
Cool, I haven’t seen Espurna before - I thought sonoff-tasmota was the only open source firmware. Have you used both before? What are the major differences?
Because I’m using the sonoff to monitor energy usage, I rarely use it as an actual switch. I think when I turn my boiler back on and start to use the timer as a switch I will add a check as you suggest.
Here’s a graph showing the last 6h of data for the power consumption and cumulative energy usage of the oven:
That is quite a frequent switching. Will be interesting to see the longevity (not being negative, just curious).
What and how are you doing the cumulative?
Not really compared the two firmwares. Espurna does what I need it to, there are frequent updates and the guy helps me with custom builds (which he then bakes back in)
I chucked him £25 donation - I figured it’s a drop in the ocean compared to my “investment”
Yeah I’ll update this thread if I have any problems.
Nice, sounds like a great developer!
The Sonoff reports energy today, so that’s all that is. Capturing the data using openhab/MQTT/mosquitto running on a raspberry pi, persistence using influxdb, graphing using grafana.
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