Difference Between Relay and Contactor

As long as it's a single phase motor drawing less than 5 amp, I don't see why not. The starting current will be higher than running current, but should be OK as it only lasts a short time. Might be worth checking with supplier to be sure.

Cheers..........Codey

Basically relay are used for controling the power where as contctor is used for switching on off the power.

The life of the device in it's application. Motor contactor is design for the high currents of the inductive load of a motor at start up. The relay is not it is design as a control circuit switching device. The springs and armature of the contactor are design to reduce the amount of time that it takes to open and close. Which reduces the arc upon opening and closing. Some of what helps this is the motion of the contacts as they make or break. A relay usually swings in a arc a contactor straight. There may also be arc reduction device around the contacts of a contactor.

If you do decide to use a relay use a two pole and switch both the hot and the neutral to the motor.

He doesn't say what size of motor is involved. On e.g. domestic heating systems the recirc pump is switched on/off direct from contacts on thermostats, which works OK for years. More complicated systems may include relays as well.

Cheers........Codey

Your right he doesn't say what the motor load will be. Just asked the difference between the two. The HVAC manufactures have years of experience with what will work and what will not. They know what the motor loads will be in designing a system to make that decision. We were provided very little on what he is trying to do.

OK, agreed......Codey

If you're going to use a control relay to operate a motor instead of a contactor, where are you getting your overload protection?

Even if they are of same rating there is a difference. Contactor offer you auto reset facility on power failure and also have over current safety features. You will have to add some electronics if you want to this with a relay.

Contactor's typically have an inductive rating, relay contact ratings are typically resistive. If you look at the specs for your "5A" relay, it will likely tell you that the inductive load rating is only 1A, and if you look at the "5A" contactor, it may tell you that the resistive rating is 9A. Those are just examples, not rules, what I am saying is do not consider specifications flippantly, it bears scrutiny.

As my ol' buddy Ray used to say..... " A relay spanks a contactor " The short of it is....a relay generally tells a contactor to go to work....

In my opinion the relay can not be used for motor control in the power circuit.

Relays contacts will not withstand the starting current .The number starts per hour is also matters.

The stalled current flow also to be taken into consideration for using the relay.