I’ll be adding a th10 too this year for the temp now I’ve got the Sonoff binding going 
- prob still keep the powr2 for the energy usage tho
I did something similar to this once for a fountain pump - I would strongly agree with the idea of using a motor contactor which is energized by the ‘Smart’ relay, rather than simply using the Sonoff / Shelly.
The points that have been made above about the motor current and general guidelines are generally very good, and most likely you would be fine with a 16A relay for a while (maybe forever…), but if it’s something you are going to be operating remotely (perhaps when you are not even in the area?) I would want to be very sure the switch is rated for the task.
A motor contactor is designed with the large inductive inrush currents and disconnect voltage spikes in mind (uses different contact materials, spring forces, etc), so it’s far less likely it will fail. For my fountain pump project, I used a Finder 22 series contactor rated at 25A continuous (1kW motor rating, which is much lower than the lamp rating. Datasheet here - there are tons of choices though - any good electrical supplier will carry a selection.
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soory for being such a nag but what do you guys think about somthing like this?
its rated for 50A , so it looks like it will cover the load? no?
its 20$ ±, and it will go to my power box no extra relays or switches…
Will work with my binding so will integrate (I would say without cloud too but cannot confirm until you add it). At 50amp too should be fine
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i am planing to flash it anyway …
i see some other brand already been flashed and tested , i will just buy that one …
i think i will go with this one… its chip , its a din rail and the power box is water proof ,so it will solve me the issue of moisture, and it will even free up space 
thank you all for all the help!
hello one more Q, will the sonoff POW get damged by the staring over current ? i plan to set it to always on?
soory for the bad draw its in MS paint
what are you trying to achieve with this?
Energy usage I believe.
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yep… its a 16A relay with power monitoring
What would be the point of using a 50A relay but routing everything through a 16A device? This is plain “weakest link” common sense.
If you’re happy to put the load through the 16A Sonoff (I would be), just do it and don’t faff with adding on more points of failure.
i want to power monitor the device…
the pump is not even 16A… the Q is will the relay get demaagd? its not going to be turned off and on many times … only under power breaks i guess
but the the 50A realy will do the switching
i dont want to use CT clamps…
It’s currently working with a 16A rated device. While not all “16A” devices are equal, this is a whopping clue.
i was trying to understand if the relay will get burned over time even if not used…
not talking about the sonoff…any relay
If it is going to be hurt by motor start inrush, it’s going to be hurt by motor starting. It doesn’t really matter if that’s once a day or once a month, though once every second will increase the chances of damage.
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