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?
we live in Jamaica. He says the input requires 2 wires but there is only 1 input
He basically is saying because the AC is 220 V. inorder to use that sonoff pow R2 he would need a slot or something like that for a 2nd input wire
In the US system there are three wires (2 hot and 1 neutral) and a ground. You have 120V from either of the two hot wires to the neutral. You have 240V between the two hot wires. It is essentially a 2 phase system produced by the pole transformer taps. The 120V "hot" wires are 180 degrees out of phase with each other. This allows lower voltage (120V) to lights and small appliances while still providing 240V for heavy loads like stoves, water heaters, and HVAC. The neutral wire is not used for 240V loads.
Your Sonoff will switch 240V AC loads in the United States system. Connect one hot to the line input and the other hot to the neutral input. On the output side connect your load to the line and neutral outputs just as if it were connected to the two lines. CAUTION! The neutral wire is NOT SWITCHED inside the Sonoff. What this means is that even when the load is turned off there will be a wire inside the appliance that is still 120V "hot" with respect to neutral and ground. This is what is concerning your electrician and in fact may be illegal with your electrical code. I agree with him, this is a dangerous arrangement.
The proper way to use a Sonoff for a 240V load in the US system is with a contactor enclosed in an approved electrical box. An added benefit is that the contactor will handle the heavy switching loads much better than the little relay inside the Sonoff.
Yes, print it out and pass it on to the electrician. You can use an inexpensive HVAC contactor rated for your AC current load and placed in a safe enclosure. The Sonoff then only operates the small coil and not the heavy load.
Yes, I agree with him. The device will work without the external contactor but it is not good practice. The Sonoff only opens the circuit on one wire leaving the other wire hot with respect to ground. 240V circuits in Europe are different than they are in the USA. There they have a simple hot and neutral. In the US center tapped transformers supply houses with two 120V lines that are combined to yield 240V.
The 2 pole contactor will open BOTH wires leaving the internal wiring of the appliance dead. The contactor will also survive the high inrush current and ringback voltage encountered when switching heavy inductive loads like HVAC motors.