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Son off Pow R2 for 220V AC Unit only has 1 input for wiring

I bought a SonOff pow R2 to work with my 220V A/C Unit . My electrician says it cant work because our 220 V system uses 2 input wires but the sonoff only uses 1. he said something about it being a europpean system being different. What can he do to work around it?


It should work  ...but...  Keep in mind that the start current (inrush) on that AC unit will be  3 to 8 times the running current so if it pulls 8 amps when running it might pull over 60 for a split second when it starts.  Also keep in mind that the ringback voltage when the circuit is opened may be several times the line voltage and cause a great arc flash.  HVAC contactors are designed to handle this.  That tiny relay inside the Sonoff is not.  So don't be surprised if your Sonoff relay contacts get vaporized after a few cycles.  This is a highly inductive load you are switching.

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My 2 cents worth, and I have said it before, If you are going to switch a 240V single phase motor load then do it right to start with.  Use the Sonoff to operate the coil of a proper contactor.  If you don't, you are going to be disappointed and potentially unsafe. 

If you don't want to wire up a 220v contactor, then add a second R2 to the other hot wire and set them up so that if one turns off they both turn off. This will be better than leaving one wire hot if your just switching the Live load.  However, this is probably not to code as you have the potential that one of the R2's won't change its power state immediately or if it can't reach your wifi, it might not change at all. 

Hi EW, I just bought a sonoff pow r2 and its coming but I haven't got it yet. I bought this item purposely to switch on and off my convection heater. This convection heater is powered by a 240 volts AC . I live in Canada and I presume that the ac line has 2 live wires which is 120 volts each pole. I've been reading this specific forum because it is similar set up of what I want to do with this sonoff switch. As what you have discuss here, You need a contactor to make it safe because If I hook it up through the Neutral terminal of the one live wire, a standing current of 120volts will still be running to my convection heater. My question is , If I use this sonoff using the method of directly connecting to the L and N input from the source and the output to my convection, would it be unsafe ? You have mentioned that if using a motor which is highly inductive and could draw a lot of current upon the start up, the sonoff couldn't handle it. But if I use it on a convection heater, I guess, it would be different from a motor load. Am I right? Do you think it would be ok. I slowly understand how your suggestion of the contactor but I need the function of power monitoring of this unit. Its one of the feature of this sonoff that I had decided to buy one. Hope you could give advise. I'm willing to try how long this sonoff will last but I just want to make sure that it is safe enough that it wont cause any fire hazards. Hope to hear your reply.



It should work from 90 to 264 volts. So normally connect L live conductor phase and N Null

@ben

As long as the current pull of the heater does not exceed the Sonoff rating it should handle starting and stopping it okay.  Switching one side of the 240V 2-wire line is not a fire hazard in general although there are a few appliances that have 120V devices internally that might still be running if connected to the hot that didn't get switched.  That is unlikely on a small heater.


My two cents worth would be that as long as you know what you are doing and recognize the fact that the appliance is not 100% de-energized, it will work fine.  It is probably not going to meet anybody's electrical code but it is just a small appliance after all.


Wouldn't it be nice of Sonoff made a two pole device?  Hey Sonoff this is a hint...switch the neutral along with the hot.  All it takes is replacing your single pole relay with a two pole and laying out the traces different on the circuit board.  It would not change the cost 15 cents and would allow folks with 2-wire 240V circuits to operate them properly.

HI EW,

   Thanks a lot for the great feedback. I've been looking for a cheaper smart switch that has 2 pole but I couldn't find one. Mostly, they are 5 times more expensive and there are only few to choose from. Hope your wake up call with sonoff will open there option to the current users of there product. They should listen of most of the needs of the users. once a lot of users are using their products, The more their business will expand. I've been looking or a water heater switch too which is using 240 volts 2 pole live. I believe that is the standard her in north America. hopefully they will also add simple basic wall switch that is cost effective. sometimes,we don't need to track down current usase in a low draw light bulbs. we need to track down current usage on heavier load devices such as water heaters. My heater have 2 elements and it's 6kw maximum . I believe that sonoff doesn't have a smart switch that can withstand this current . hope they will add more complete line up of device that will be useful for the rest of devices in the household. we don't want to have multiple apps for multiple devices. one apps that covers all the smart devices will be ideal. That's why I stick to sonoff and ewelink to run all my add on smart switches and plugs. thanks again EW. I appreciate your reply. 


If you have only the L phase and zero N of the appliance, it is enough to switch off only one pole, namely the phases. Zero switching off is unnecessary. On AliExpress, 63 Ampere contactors controlled via eWelink can be found.

Thank's Robert for the advise. My heater is using 240volts ac with 2 live wire ( 2 pole) . I saw a circuit breaker wifi switch that is 50amps capacity in ali express, I guess that switch will work because it will cut off I believe the 2 pole connection and it acts like a circuit breaker switch ,, nevertheless, It doesn't have an overload protection circuit. So it will work with a high ampere 240volts  appliance like water heater which is usually rated consumption of 6kw. 

btw, it's also inexpensive but I will try the sonoff which acts similar. the sonoff however will cut only one pole and not both but have a power monitoring features which I really want to use. 

thank's again. 

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