Magnetic or manual starter

[Dave Bureau]

Looking for the best place to get a motor starter for a 2hp 1ph motor.
Dave

[Ronald Mancini]

Motor starters are nothing but switches unless they have peripheral functions. Magnetic starters switch the motor on, but when power is lost the starter drops out and the motor does not come back on when the power comes back. Some people view this as a safty issue.

Magnetic starters are expensive, but lower priced units can be purchased at Grizzly and Ebay, and jarring a magnetic starter machine can cause the magnetic starter to drop out.

A standard two pole switch similar to those you have in your house can be used to control the motor if it has an adequate current rating. One hp = 746 watts so you need 746 times 2 watts == 1492 watts. Watts = voltage times current and voltage usually is 220 volts for 2hp motors. You need at least 7 amps so the standard 15 amp switch will work fine. I would buy a standard 20 amp switch that costs a little more but is adequate for the next machine.

[Rick Fisher]

Overload protection for the motor is another feature most often offered by a Mag Starter.. A smaller motor like that may have it already, if it doesnt, the Mag Starter will offer protection.

[Tom Veatch]

...
A standard two pole switch similar to those you have in your house can be used to control the motor if it has an adequate current rating. One hp = 746 watts so you need 746 times 2 watts == 1492 watts. Watts = voltage times current and voltage usually is 220 volts for 2hp motors. You need at least 7 amps so the standard 15 amp switch will work fine. I would buy a standard 20 amp switch that costs a little more but is adequate for the next machine.

You really need to be a little cautious there. Standard residential switches are not designed for inductive loads. There's a much different voltage-time profile generated when the circuit powering a motor is made or broken. Switches designed for motor control will be rated in HP as well as amperage. And generally the HP rating is significantly less than a straight volt-amps wattage/746 would indicate. Not saying what you suggest wouldn't work, but don't assume that a switch rated for a particular amperage is rated for an inductive load at that amperage.

[Tom Veatch]

Overload protection for the motor is another feature most often offered by a Mag Starter.. A smaller motor like that may have it already, if it doesnt, the Mag Starter will offer protection.

It's always been my assumption, perhaps incorrectly, that the difference between a "Magnetic Starter" and a "Magnetic Switch" was the presence of overload protection (commonly called "heaters"?) in the "Starter" and their absence in the "Switch".

[Matt Meiser]

I get stuff like that from FactoryMation.com or Ebay. With some persistence, I've gotten some pretty good deals on name-brand starters on Ebay, some brand new. But you need to know what you are looking for with respect to size, coil voltage, etc. Since most of my applications have been replacing non-magnetic switches, I just pull off the overloads.

[Rod Sheridan]

Manual and magnetic starters can incorporate overload elements or relays.

You need to know the motor full load current rating when sizing overload protection for your motor.

A magnetic starter will provide restart protection following a power outage, as the contactor will drop out if the power is removed.

This can be a significant safety feature if there is a momentary power outage. Sawing something, then having the lights go out and then back on again is bad enough. It can be worse if the saw starts up again.

I haven't heard of magnetic starters dropping out from impacts, however there have been reports of the cheap ones closing when subject to vibration or impact.

Regards, Rod.

[mickey cassiba]

At Delta we did get a batch of mag switches that were defective in that they would open when the switch enclosure was hit lightly. They wer for the 3HP 1ph Uni's. Can't remember the manufacturer now, but to my knowledge they were recalled and replaced. Made in China, I suspect, but what isn't these days? Haven't seen this problem since, all of my tools(except the hand units) have mags on them.

[Dave Bureau]

can I buy a mag starter rated for 5 hp and install a 2hp motor? I'm thinking that i may soon change to 5 hp but i want to get the machine running for now.

[Danny Burns]

Just as an aside, I would also not rely on any a switch to do it's job, when working on a machine, so always un-plug a machine when working on it.

[Rod Sheridan]

can I buy a mag starter rated for 5 hp and install a 2hp motor? I'm thinking that i may soon change to 5 hp but i want to get the machine running for now.

Yes, if the overload relay can be adjusted low enough for a 2 HP motor.

Regards, Rod.

[Matt Meiser]

Also yes, if the overload functionality isn't necessary in your application.

[Curt Harms]

You really need to be a little cautious there. Standard residential switches are not designed for inductive loads. There's a much different voltage-time profile generated when the circuit powering a motor is made or broken. Switches designed for motor control will be rated in HP as well as amperage. And generally the HP rating is significantly less than a straight volt-amps wattage/746 would indicate. Not saying what you suggest wouldn't work, but don't assume that a switch rated for a particular amperage is rated for an inductive load at that amperage.

I had a Chinese switch (not even a light switch) weld itself shut in the on position:eek:. Thank heaven it was on a bandsaw I no longer have and I was able to simply unplug it and replace the switch with something more suitable. If it had been on a different machine or different circumstances life could have been "exciting"

[Ronald Mancini]

The double pole 25 amp switch is made for motors---light bulbs don't come that big. Magnetic motor controls sometimes contain overload coils, but you can get the same result by sizing a circuit breaker. The choice depends on how much you want to spend and if you think safty is an issue..

[Rick Fisher]

I had a Chinese switch (not even a light switch) weld itself shut in the on position:eek:. Thank heaven it was on a bandsaw I no longer have and I was able to simply unplug it and replace the switch with something more suitable. If it had been on a different machine or different circumstances life could have been "exciting"

Wow..

I had a mag starter out of the box stuck one of the hot wires in the hot postion..

Since then, I really dont trust them..

Oddly, it was on a bandsaw as well.

[Bob Aquino]

can I buy a mag starter rated for 5 hp and install a 2hp motor? I'm thinking that i may soon change to 5 hp but i want to get the machine running for now.

Would depend on the switch, but most of the new plastic ones have a variable setting for current so as long as it would go down to the lower current, it should not be an issue.

The older style starters (think larger metal case, very heavy, robust contacts, remote pushbutton switches, Etc.) used interchangeable devices called "heaters" that were rated in amps. To change the starters current overload rating, you have to put in a different set and they were all different depending on the manufacturer and even the model and series of the starter. You can still find these heaters, Southland Electric is one source. The starters were rated for current and size as Nema size 0, Nema size 1, etc, depending on the load you needed to control. They can still be found for relatively cheap money on the bay or over at OWWM on the classified section of the forumn : http://owwm.org/viewforum.php?f=4&sid=2155e0304062e3b05ee01ccb5fcac308 If it were me looking to retrofit one onto a machine, I would go for one of the older, industrial quality starters rather than the plastic ones commonly found on the new stuff.:rolleyes: