Good day,
I'm building a simple system for a 1 horsepower water pump. It runs on 220V(750W). I want to remotely control it using an arduino/relay. I am planning to use this relay:
Is this relay adequate enough? If not, what be a good alternative?
Thanks.
I don’t trust the 10A rating on those. They are more likely 2-4A as similarly sized OMRON relays.
If you plan on using the relay more than once, then get an industrial relay rated for a 1 HP motor. It will have contacts about 1/4 inch in diameter. You also need a snubber circuit across the relay contacts to reduce the arcing when they open. The arcing erodes the metal on the relay contacts.
You can use the little relay to control the motor relay and that will likely be ok for a while. So buy more than one!
Paul
I agree with the previous post. Use that relay and I suggest you buy a large pile of them. We read in this and other electrical/electronic forums about their failure rate at much lower currents than you see on those relays. I suggest you invest in a motor starter contactor rated for your 1 HP motor. Look for the full-load current rating on the motor’s faceplate and choose a motor starter contactor accordingly. You may also want to include thermal overload protection which comes on motor starters. Buy once and cry once. Choose your coil voltage accordingly and drive it with a transistor or if you want a logic level MOSFET. Oh yes, and when those cheap relays fail they fail with welded contacts in most cases which depending on your pump configuration could lead to a dry running pump.
Ron
Paul_KD7HB:
If you plan on using the relay more than once, then get an industrial relay rated for a 1 HP motor. It will have contacts about 1/4 inch in diameter. You also need a snubber circuit across the relay contacts to reduce the arcing when they open. The arcing erodes the metal on the relay contacts.You can use the little relay to control the motor relay and that will likely be ok for a while. So buy more than one!
Paul
Thank you for your input. I'm relatively new when it comes to electronics. Can you please add a photo or at least a brand name for an industrial relay?
Thanks
And even if the relay itself is really good for 10A, I wonder if the pcb traces are?
(That said, 750W at 220V is "only" 3.5A 
)
edit: next post reminded me about stall current....
Don’t forget about stall current.
A motor needs a fair amount of current to start up and if the motor encounters load it’s current will shoot up. Full load current of 1 HP motor at 220v is about 8A. A motor like this can make a 10A circuit breaker trip or at the very least, dim lights on the same circuit.
wolframore:
Don’t forget about stall current.
I had....
wolframore:
Don’t forget about stall current.A motor needs a fair amount of current to start up and if the motor encounters load it’s current will shoot up. Full load current of 1 HP motor at 220v is about 8A. A motor like this can make a 10A circuit breaker trip or at the very least, dim lights on the same circuit.
Thank you for all the input. I'm learning a lot. Been spending a lot of time studying Ohms Law.
kidlat14:
Thank you for your input. I'm relatively new when it comes to electronics. Can you please add a photo or at least a brand name for an industrial relay?Thanks
Normally I would make a suggestion but not knowing your location and what is available to you it's hard to suggest. I would just do a Google of 1 or 2 HP motor starters single phase.
Where I am there are plenty of sources but just as an example:
Then I consider enclosure or open frame. Depends on the environment. 
Ron