I am trying to control my Air conditioner via MQTT protocol. I just want to make the power on and off. How can I calculate the relay current rating for 1126 Watts of power? Link to AC model: https://www.amazon.in/Voltas-1-2-Split-155-CY/dp/B00LWRDJEE

Also which is better for this application ( SSR/electromechanical relay).

Experts please, Help.

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    \$\begingroup\$ Asking for help in figurimg out the proper specifications is on topic. Asking for part recommendations is not. You can edit your question and remove that part. If you don't, your question might be closed. \$\endgroup\$ – JRE Jun 27 '18 at 7:40
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    \$\begingroup\$ Not being able to convert watts to amps on your own suggests that you'd better leave mains wiring to a qualified electrician. \$\endgroup\$ – Dmitry Grigoryev Jun 27 '18 at 9:28

Assuming you are using a 220VAC mains supply, 1126 Watts will consume about 6 Amps of current, you can calculate it from the following Online Calculator.

Average mechanical relay have a life cycle of 100,000 cycles which means it can be used for a long period of time. Also its not mandatory to use the fast response of the solid state relay. Because your application is going to switch the air conditioner on and back off once every half an hour.

The starting current of AC motor is usually 2 - 2.5 times the running current, which is equal to 15 Amp.

So a typical 220VAC 20Amp mechanical relay will fit your application well.

  • \$\begingroup\$ Average mechanical relay life cycle is usually guaranteed for 10^5 cycles, but the conclusion is the same \$\endgroup\$ – Lelesquiz Jun 27 '18 at 12:42
  • \$\begingroup\$ You are right, but 10^5 = 1,000,000 as I mentioned ;) \$\endgroup\$ – Ahmed M.Zahran Jun 27 '18 at 21:49
  • \$\begingroup\$ Is there a starting current surge to be considered with this application? \$\endgroup\$ – Solar Mike Jun 27 '18 at 21:52
  • \$\begingroup\$ Yes, because of the external unit motor. \$\endgroup\$ – Ahmed M.Zahran Jun 27 '18 at 21:55
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    \$\begingroup\$ Glad you added that starting current detail - makes a big difference in the relay... \$\endgroup\$ – Solar Mike Jun 27 '18 at 22:45

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