What switch for a 3 phase motor?

[Mark Gibney]

I am replacing a 1 hp 3-phase motor on a bandsaw (D&W 20") with a 3 hp 3-phase motor.

What is the appropriate switch to use? A simple toggle switch, or the switch that came with the machine? - it's a Square D push button switch. Here's a photo.

397650

This switch is massive. If it's the better of the two choices I'll use it but I like the idea of something neater - I'm putting some effort into the machine so I'm invested in the aesthetics.

If a toggle switch would work is there a brand you like?
Is there another option I don't know about?

thank you all, Mark

[Rollie Meyers]

You need a switch rated for the motor and that has overload protection, the SQ D manual starter shown has O/L protection, I prefer a magnetic starter over a manual starter.

[Mark Gibney]

Rollie, what do you prefer about a magnetic starter over a manual starter?

And isn't the motor protected by the circuit breaker?

thanks, Mark

[Bill Dufour]

That is not a switch, it is a motor starter. It should be labeled for max Horsepower. I doubt it can handle 3hp. You relay need a contactor with overloads with a low voltage switch. I recommend buying used from the bay with adjustable overloads. You must know FLA on the new motor before you buy anything.
PS: Low voltage means 120 volts or less, no need for a transformer.
Bil lD.

[David Kumm]

A size one or size 0 with appropriate heaters. A mag starter will not restart a machine if the power goes off and then comes back on. It is a better option for most 3 hp motors. Dave

[Bill Dufour]

[QUOTE=Mark Gibney;2870335]Rollie, what do you prefer about a magnetic starter over a manual starter?

Manual starters are too slow acting for high amps. this leads to arcing which eats up the contacts quickly. Power companies use air to blow out the arc on their manual switches.
Contactors are just built more heavy duty and will last longer and not get welded shut. Also wired correctly a contactor will open if power is lost and not restart unless the go button is pushed again.
The breaker is sized to protect the wire in the wall not the load.
The software says the above statement is too short so i adding this

[Mark Gibney]

Bill, David, Rollie - thanks.

[Brian Backner]

For large motors, magnetic starters are much safer. If you lose power - a squirrel arcing itself across the terminals on a neighborhood transformer and causing a 2-3 seconds pause, or you open the breaker by overloading the tool with too deep a cut - the starter will open and require you to turn it back on. If you lose power in a big storm and it takes the utility several hours to get things back on line, will you have remembered to turn the machine OFF before you leave your dark shop? This also allows you to correct any problems that might have caused the breaker to trip in the first place. It can be a little annoying - needing to take an additional five seconds to turn the starter on - until you think about how much safer it is. While you can certainly use the breaker back at the panel to protect the wiring, the use of "heaters" - i.e., fuses - in the starter allows you to fine tune the settings as heaters come in various "speeds'.

[Mark Gibney]

Bear with me if this is a roll-your-eyes question, I'm not so familiar with 3-ph power -

the motor FLA is 8.2 amps (it's 3 hp 3-phase 240 V)

I just found this magnetic starter in a box of electric parts I have.

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Its a Big Horn 18833 3-ph 240 V 3 hp 8-12 amp magnetic switch.

Will this do the job?

thanks, Mark

[Matt Mattingley]

Bear with me if this is a roll-your-eyes question, I'm not so familiar with 3-ph power -

the motor FLA is 8.2 amps (it's 3 hp 3-phase 240 V)

I just found this magnetic starter in a box of electric parts I have.

397844
Its a Big Horn 18833 3-ph 240 V 3 hp 8-12 amp magnetic switch.

Will this do the job?

thanks, Mark
I’m a bit confused Mark. Do you have three-phase in your shop? Is it natural three-phase or is it generated a three-phase? What is the end result with the motor? I personally love the great big old Square D starter controllers. You can buy Manuel drum switches or manual motor starter switches that look very similar to a heavy duty light switch for three phase). But usually Manuel switches do not have overload protection for the motor.

[Mark Gibney]

Matt I have a 3-phase panel at the shop. The shop is a rented unit in an older industrial park.

Are you voting that I keep using the SQ D starter over this magnetic starter?

[David Kumm]

I've had much better long term luck with the old NEMA starters than the new small module plastic type, especially if they are a low price made in China type. Not dissing China here but machines with switch and electrical issues are often traced to buying cheap components. In the past, Euro companies like Moeller, Siemens, Sprecher Schuh and others cheapened up their internals which caused problems. I don't know if that is an issue anymore but similar to old large frame motors, I've had very few problems with the old starters and contactors vs the newer modular stuff. NOS Sq D, Allen Bradley, or Cutler Hammer can be found pretty cheap. The enclosure is usually the most expensive part of the starter. Dave

[Bradley Gray]

I have had good luck with the old square D manual starters as well.

Also, I have bought used starters and starter heaters from this place with good results:

http://www.southlandelectrical.com

[Tom Bender]

Hi Mark
Will you be hard wiring it or will there be a cord with a plug? If hard wired you will want a lockable disconnect for safety. It may be a code requirement, I don't know. If you can unplug it, that should be ok.

Starters can incorporate a disconnect or you may need a separate device. It should (must?) be within sight of the motor. The circuit breaker in the panel will probably not suffice.

[Tom Bender]

A starter can have auxiliary contacts to let you pull it in with a low voltage switch (or two) so the bigger hardware can be mounted out of convenient reach. Multiple switches could be useful if you want to be able to start or stop from different positions.