# Do I Need A Magnetic Motor Starter?



## Susan_in_SF (Nov 18, 2018)

Hi Guys,
So, I was browsing Craigslist  (very dangerous since I already have too much stuff) when I saw an ad for a magnetic motor starter.  I didn't know anything about these devices, so I did some research online.  I wanted to know if I needed a magnetic motor starter.  After 20 minutes of reading and not getting an answer, I thought I'd turn to you "gentlemen," and any "ladies" out there.

As most of you guys already know, I am a measly renter working out of a 1 car garage.  Have 2 outlets on different circuits in my garage.  My washer and dryer are on a 120v 20 amp circuit (I have a gas dryer), and my garage ceiling outlet (the apt mgmt installed it for my garage door opener and light) is, I am guessing, 15 amp ( It is "community" electricity so I don't pay for using this outlet.

With using my metalworking machines, I can run my Bijur micro droplet coolant system and the air compressor off the 15 amp ceiling outlet while the machine is on my 20 amp outlet.

Well, having limited power in my garage has forced me to be creative while still keeping safety in mind.

I wish I never encountered Bill Pentz's website at:  http://billpentz.com/woodworking/cyclone/

After reading his blog on the horrors of woodworking dust, a 1 hp dust collector just wouldn't do for me anymore.

However, with my garage's current  electricity situation, I can only run one machine at a time (which is fine since I would be by myself), and the dust collector would have to be run off the 15 amp "community" outlet.  However, the 110v, 15 amp circuit won't work for motors greater than 1 hp.

Ok, I realize that this site is for machinists, not woodworkers. However, this is the only site that I am an active member of.  Plus, I also plan on building a separate dust collector for when I am grinding metal.  I already have a 12 inch aluminum impeller for it.  Did I mention Overkill is my middle name?

Going back to the Bill Pentz blog, he mentioned how ineffective a 1 or 1.5 hp dust collector actually is at getting those nasty little particles.

How would I be able to have a larger hp dust collector if all I have is a 15 amp outlet?  

Well, this is where I tell you my plan, and this is where you get to judge if I am either really smart or really stupid.   

**Warning** --super long story with probably too much detail (Crap, maybe I should have put this warning at the beginning of the post)

First of all, my lathes and mills can use a VFD as a phase converter, along with a step up transformer to run 3 phase 220v motors with variable speed.  I read online that lathes and mills can get away with not using a rotary phase converter and can use a VFD instead since they just need to the converter to start the motor.

With dust collectors, on the other hand, they have to use a rotary phase converter due to running at full load, and need the converter continuously.

So, for the dust collector, I picked up (at a deal) a Quick 220 voltage converter off Craigslist.  This gadget will take 2 non-GFCI 20 amp 110v outlets, and will create a 220v outlet. Since I am a renter, I can't be rewiring the place, lol.  

I looked at my circuit options, and decided to use the 20amp circuits for the garbage disposal and for the dining room outlets.  All I have to do is drill a hole from my storage closet wall to the garage on the other side to run the heavy gauge power cord.  Then, should I move out, just spackle the hole up.

I could have tried to use my 3000 watt step up transformer, but just felt the Quick 220 was better for the rotary phase converter.  

Then, after researching what size rotary phase converter I needed (taking into consideration that the converter/slave motor should be at least 50% larger than the motor running the machinery), I bought a 5hp rotary phase converter for $135 off an ebay guy who makes these as well as "kits".

I then picked up, off of ebay, a 5hp Baldor motor for $50, plus $50.03 shipping, and a 2hp Baldor motor off craigslist for $60. 

Fyi, I have gotten incredible motor buys off of Ebay when I use the "best offer" option with sellers who are liquidators.  I once bought a 2hp Baldor Reliance vector motor, with encoder attached, for $95 plus free shipping.

I feel that it doesn't hurt to offer these guys super low offers since they are eager to move their inventory, and they have access to much cheaper shipping rates than the regular Joe guy selling a motor that he no longer uses.

So, I think I did ok.  The total cost of the 5hp rotary phase converter and 2 motors cost just under $300.

I plan on hooking up the Quick 220 outlet cord into the 5hp rotary phase converter.

I bought the 2hp Baldor motor since I felt 2hp was sufficient for my dust collector.  I then read conflicting info online in regards to whether there is motor power loss with rotary phase converters.  The 2hp and 5hp motors are TEFC.  However, if I am going to have power loss, I can use my spare 3hp Baldor motor, but it is not TEFC.  3hp would be the absolute largest motor I can use with this setup.

Ok, now that I told you all this info, I will return to my original question:  
Do I need a magnetic motor starter?

Thanks in advance for any advice/feedback/schooling you may have for me 

Susan


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## pstemari (Nov 18, 2018)

Susan_in_SF said:


> ...So, for the dust collector, I picked up (at a deal) a Quick 220 voltage converter off Craigslist. This gadget will take 2 non-GFCI 20 amp 110v outlets, and will create a 220v outlet.



I'm rather suspicious of this gadget. The two outlets must be on opposite phases for it to work. The website says it's UL-listed and has interlocks to prevent problems, but I wouldn't trust that unless I verified the listing with UL.

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## Susan_in_SF (Nov 18, 2018)

pstemari said:


> I'm rather suspicious of this gadget. The two outlets must be on opposite phases for it to work. The website says it's UL-listed and has interlocks to prevent problems, but I wouldn't trust that unless I verified the listing with UL.
> 
> Sent from my Pixel XL using Tapatalk


Understood.  I will later today do some research if anyone has had issues with this gadget.


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## chips&more (Nov 18, 2018)

Time to move! Forget about buying a house. Just buy some land and put a GIANT quonset hut/airplane hangar on it! And they make VFD’s with 1ph 120v in with 3ph 240V out.


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## JimDawson (Nov 18, 2018)

Susan, from what you describe it sounds like you are maxing out your available power now.  I'm not excited about those 220v converter thingies, and that won't add to your power, but might give you 15 amps of 220V.  Why do I say 15 amps?  Because you would have to plug one cord into the 15 amp outlet and the other into the 20 amp outlet in order to get 220V.  BUT.... This assumes that each of those outlets is on the opposite leg of the 220, if they are on the same leg then it won't work at all.

A 5 HP RPC, loaded, is going to draw about 23 amps of 220V, or about 46 amps at 110V  Even with a 110-220 step up transformer at best you are only going to have about 10 amps available at 220V.

Bottom line is that you need more power.  I would recommend moving out into the country somewhere with a nice big shop.


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## ttabbal (Nov 18, 2018)

I don't know about the original question, but if you have a 220V outlet nearby for a clothing dryer, you can make an extension cord for it. I did that while renting a place that had an unused one due to having a gas dryer. Even if you have to share, dry clothes are overrated..  

The 2 120V to one 220V adapters are safe, but you have to verify that they are on opposite phases. It's not difficult and the commercial units probably have simple detection systems to help you out. I've built adapters that go both ways. Nothing to it. A little common sense goes a long way with these sorts of things.


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## Bi11Hudson (Nov 18, 2018)

You actually have several questions, as points of conversation. All in all, there is *no* good news. You have stretched your electrical service to about its' limits now. Going any further will require at least an electrical upgrade. As a renter, you know how far that would go. Like others have said, relocation is the best answer.

Now, to your basic question. A "motor starter" is simply a *very* large relay with the addition of a thermal protective circuit for the motor. I personally recommend a starter for some 3/4 HP motors that run a high(or continuous) duty cycle. That's both single and poly phase. At one(1) HP, that's *any* motor. My personal opinion, now. There are 5 HP motors that run off a disconnect but I don't approve in the slightest. A fire just waiting to happen. A burnt motor at best.         _Such devices are *not* sharable. One motor per starter. Period, non-negotiable. _

There is *one possibility* here. You state you have a gas dryer. Look on the back wall for a "crowfoot" plug, behind or very near the dryer. If there is one, there is a source of 220-240 volts with 30 amp capacity. If it's there*... ... *That's your only out, unless, of course, you don't need the kitchen range. With a teenager in the house, I won't go there. I have pulled such shenanigans in the past, at remote office locations. But won't recommend it.

Your second question is about rotary phase converters. The first question would be "_how many motors_" will you run from it. If it's just the dust collector, no others, I have a suggestion for you. A rotary converter is simply a three (3) phase motor running with a few capacitors off of single phase power. Since the dust collector is run continuously, let it be its' own converter. That would cut down a *bit* on power usage too. A converter is sorta thirsy. There are many web sites on doing 3 phase from single conversion. I used to have it on my web site and removed it for liability reasons. It is(was) a corporate site and the insurance folks reduced my rate when I removed it.

The bottom line here is that, unless you have a dryer plug or tap into the range, it ain't gonna happen. At best, you will only trip breakers. *At worst, the whole building will burn down*. Don't go there. California has enough fires already. Dont start another.

Bill Hudson​


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## ThinWoodsman (Nov 19, 2018)

Do you have access to the electrical panel for the garage? Hit the mains disconnect, add a 20-amp (or, hell, why not 50!) breaker, wire to a socket, claim ignorance when you move ("I recall the handyman elbow-deep oin the thing cursing, one day"). 

Much harder if you only have access to the apartment breaker, as it's going to be flush with the drywall so you'd have to punch a couple holes to run the wire.

And I agree with pstemari, device sounds a bit dodgy.



JimDawson said:


> I would recommend moving out into the country somewhere with a nice big shop



Worked for me!


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## markba633csi (Nov 19, 2018)

You may be in a part of San Francisco with really prehistoric wiring- maybe even going back to the earthquake
If you don't have a 220 volt stove or dryer outlet you are pretty limited in amperage
mark


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## RockingJ (Nov 19, 2018)

If I hear of another great fire in S.F. I will know where it started! You are already running more that I would recommend on the existing wiring, don’t add more!

The use of a contactor to control motors allows the contacts in the contactor to take the power surge when the motor starts up. This way the circuit switch doesn’t arc across the contacts every time the circuit is energized or de-energized. The contactor has much larger contact points that can take the spark better.

Another thing is you should have a motor starter in the input circuit to the rotary phase converter, the motor starter is simply a contactor with an on/ off switch and overload protection. It also will shut off the circuit if there is a power loss. This prevents the RPC from restarting automatically when power is restored.



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## P. Waller (Nov 19, 2018)

Everyone needs a magnetic motor starter, this is how electric motors work (-:
Rotating magnetic fields make the wheels go round and round.


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## Susan_in_SF (Nov 24, 2018)

Bi11Hudson said:


> You actually have several questions, as points of conversation. All in all, there is *no* good news. You have stretched your electrical service to about its' limits now. Going any further will require at least an electrical upgrade. As a renter, you know how far that would go. Like others have said, relocation is the best answer.
> 
> Now, to your basic question. A "motor starter" is simply a *very* large relay with the addition of a thermal protective circuit for the motor. I personally recommend a starter for some 3/4 HP motors that run a high(or continuous) duty cycle. That's both single and poly phase. At one(1) HP, that's *any* motor. My personal opinion, now. There are 5 HP motors that run off a disconnect but I don't approve in the slightest. A fire just waiting to happen. A burnt motor at best.         _Such devices are *not* sharable. One motor per starter. Period, non-negotiable. _
> 
> ...


Thank you Bill for your honest and wise response


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## Susan_in_SF (Nov 24, 2018)

markba633csi said:


> You may be in a part of San Francisco with really prehistoric wiring- maybe even going back to the earthquake
> If you don't have a 220 volt stove or dryer outlet you are pretty limited in amperage
> mark


Hi Mark,
I live in a 2 story townhouse style apartment.  Thankfully, due to these buildings being built in the late 1960's, I don't have to worry about lead pipes for our water, and the I have plenty of 20 amp circuits in my breaker box (plus having centralized heating - some of our older victorians here have weird heaters powe red by steam). As for my stove and dryer, my unit uses gas where the kitchen has 3 separate 20 amp circuits, and the washer/dryer has a 20 amp circuit as well.


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## Susan_in_SF (Nov 24, 2018)

RockingJ said:


> If I hear of another great fire in S.F. I will know where it started! You are already running more that I would recommend on the existing wiring, don’t add more!
> 
> The use of a contactor to control motors allows the contacts in the contactor to take the power surge when the motor starts up. This way the circuit switch doesn’t arc across the contacts every time the circuit is energized or de-energized. The contactor has much larger contact points that can take the spark better.
> 
> ...


Thank you RockingJ for the motor starter suggestion.  I will definitely look into getting one now.


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## Janderso (Dec 15, 2018)

Susan, your stories are much better than television!


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## just old al (Dec 15, 2018)

While you might not need a motor starter per se, I might consider adding an NVR. I am slowly doing that on all of the spinny bit machines here in my workshop.

An NVR is a push-button switch panel with a relay built into it - simple device. The good part of it is that should the power go off and then back on, the machine will not restart as the contacts of the relay hold the relay energized as well - the buttons do nothing but provide a momentary electrical contact to draw in the relay. 

This gadget is nice for a few reasons. It provides push-button start and stop for the machine (the stop being a big 'OH S#$% button!) as well as the NVR functionality (see above). What it does not provide is overcurrent protection.

What prompted me to do that is the forward/reverse drum switches on my lathes and mill - they have no center stop at off. In an emergency, there's no 'OH S#$% function there - going from forward to reverse simply leaves the motor energized and spinning as the start winding is already de-energized.

Just a thought - Alan.


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## rwm (Dec 15, 2018)

As long as you have two circuits on opposite phases the "220 voltage converter" will work fine. It just grabs a +120v and a -120v supply at the same time.
As others have said the overall power available is the limiting factor. 1 horsepower equals 746 watts. No way around that. If you need to run a 2 hp motor you must draw a minimum of 1492 watts not allowing for power losses, inefficiency, and higher startup currents. If one of the circuits has a 15 amp breaker that will likely not handle it. If you had 2, 20 amp circuits on opposite phases available you might be able to safely run 2 HP. That could theoretically provide 2400 watts. Derating to 75% gives 1800 watts. If you put a phase converter in the circuit I am not sure how much efficiency you would lose in addition to the above issues.
Other may disagree with the use of the word safely.
Robert


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## P. Waller (Dec 15, 2018)

Yes you need a magnetic starter as they are chock full of magic that is not easily available elsewhere.
They will start a motor and stop a motor.
They will start a motor that is out of direct line of sight, in another room for instance.
They will start and stop a motor when you are not there to push the start and stop switches manually.
They will allow the shutdown of a motor that has gone beyond its operational parameters without human intervention.
They will not defeat SkyNet however so be very careful (-:


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## 7635tools (Dec 17, 2018)

RockingJ said:


> If I hear of another great fire in S.F. I will know where it started! You are already running more that I would recommend on the existing wiring, don’t add more!
> 
> The use of a contactor to control motors allows the contacts in the contactor to take the power surge when the motor starts up. This way the circuit switch doesn’t arc across the contacts every time the circuit is energized or de-energized. The contactor has much larger contact points that can take the spark better.
> 
> ...



Not entirely true. Depending on how the control for the starter is wired it could automatically restart. 


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## WCraig (Dec 17, 2018)

7635tools said:


> Not entirely true. Depending on how the control for the starter is wired it could automatically restart.


I've never seen that.  How does that work?

Craig


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## pstemari (Dec 17, 2018)

Normally a contactor is wired with a momentary switch and an auxiliary contact in parallel to latch the circuit on. You can also wire a on/off switch directly to the coil, with no auxiliary contacts. That configuration doesn't protect against restarting after power loss/restoration.

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## 7635tools (Dec 17, 2018)

pstemari said:


> Normally a contactor is wired with a momentary switch and an auxiliary contact in parallel to latch the circuit on. You can also wire a on/off switch directly to the coil, with no auxiliary contacts. That configuration doesn't protect against restarting after power loss/restoration.
> 
> Sent from my Pixel XL using Tapatalk



Exactly. In basic motor control there is what’s called 2 wire control and 3 wire control. Typically 2 wire control is a maintained switch that will turn on the starter. If the starter loses power the switch is still closed so when power is restored the starter energizes. 3 wire control uses momentary contacts and a holding contact on the starter to energize it. Therefore if you lose power the starter won’t turn back on units you push the start button. 


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## P. Waller (Dec 17, 2018)

Some starters employ very simple VFD technology, they will start an unloaded motor slowly with a low starting current and a smooth ramp up speed rather then the all or nothing approach that a simple contactor  employs, they cost considerably more however. Often called a Soft Start by electricians.

Soft start pneumatic valves are often used in distributed pneumatic control systems in order to keep many of the actuators from operating wildly upon start up, these are also not inexpensive.

Buy what works for you in a particular situation.


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## rwm (Dec 17, 2018)

BTW. I have a 120v magnetic starter for sale if you or anyone else needs one.
Robert


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## agfrvf (Dec 19, 2018)

If you find 2 outlets where the small holes do not have continuity between two outlets you can pair them for 220v single phase.


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