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I am using Omron G5RL-1A-E-HR relay in my project with these specs:

Relay specs

I am using the high inrush type with max allowable current of 16 amps. I have used with water heaters up to 2 kW and air conditioners rated approx 2000 VA. Good thing about air conditioners is that they have a stabilizer which also delays the turn on of air conditioner. As such, there is no risk of high inrush current. However I am not sure if I turn it off when the air conditioner is running. Anyways, I haven't seen a failure in almost an year.

What's the max hp pump that I can put on this relay for a reliable operation? This case is different from air conditioner because motor will pull current as soon as I turn the relay ON. Do I need to make any changes to the circuit to improve it's life?

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For motors, you should be looking at relay ratings that specifically apply to motors. For NEMA ratings (USA) look for horsepower (Hp) ratings. For IEC ratings (worldwide) look for IEC Utilization categories.

For the Omron G5RL-1A-E-HR relay, use the ratings highlighted below. LRA and FLA mean motor locked rotor and full load amps

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Note that the number of test operations is 6,000 for the motor ratings vs. up to 50,000 for the other ratings. The number of test operations is probably a good indication of the expected life. For longer life, you might consider using a motor contactor. If the relay is switching a lower current than the maximum rated current listed, that should extend the life. Look at the Moron durability curves.

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