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  1. #1
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    Default Help with switch for motor

    This seemed like the most appropriate place to ask this but if it should be somewhere else I apologize.

    I am putting a bigger motor I have laying around onto an old lathe. The motor is 5hp single phase 230V 21A according to the plate. Originally the lathe had a under powered 120V 3/4hp motor. My problem is I need a new switch to turn on the 230V motor but I don't know exactly what I need. Price is the main concern this project has a very small budget. I assume I need a 2 pole switch rated to more than 21 amps but most of the on/off switches for tools and stuff I have found have a HP rating between 1-3HP and less than 21amps. Is there a cheap and simple way to turn the lathe on/off with this size motor? Not sure if it is relevant I am located in Canada.

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    A few questions first. Do you intend to run this in reverse? Does this lathe have a gear box that reverses it?
    Do you have to start and stop the motor everytime you stop cutting? If it is a straight up and start with reversing gearbox and does not have to stop and start the motor many times during use get a simple 30amp double pole toggle switch similiar to a light switch should be fine. They are about $15.00 US. If you have to stop and start many times get a magnetic starter with reverse if needed. They are not that expensive. I will look I may have a 5hp rated magnetic starter without reverse if you can use that for the price of shipping. Keep it simple is the best route.

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    It is on an antique belt drive lathe so no gear box. It will get turned off whenever I want the spindle to not turn. I don't need reverse since the chuck threads on. Its about as basic of a set up as they came and for my needs that's good enough. It is over 100 years old, 16x36, line shaft drive machine. Though at some point it was converted from line shaft.

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    You can't go by amps alone, a switch must be rated for the HP, in your case 5HP. Yes, it will need to be 2 pole. What you can likely find with the right ratings will be called a "Manual Motor Starter".

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    Would this simple 30amp 2 pole switch work? It's rated for the right amperage and voltage but it doesn't say anything about horse power but came up on amazon when I searched manual motor starter. I will admit I don't know much when it comes to motors and I may be over simplifying what it is I think I need and will work.

    Leviton 3032-2I 30 Amp, 120/277 Volt, Toggle Double-Pole AC Quiet Switch, Extra Heavy Duty Spec Grade, Self Grounding, Back and Side Wired (Ivory): Amazon.ca: Tools & Home Improvement

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    I don't know if the link you have noted above is a joke or not, but NO, it's not an acceptable switch..at all! Here is a nice IEC contactor with the appropriate O/L relay and a enclosure for about as cheap as you could ever find. I'd buy this setup in a heartbeat.

    https://www.amazon.com/Magnetic-Elec.../dp/B00ATCCYXK

    Stuart

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    BE CAREFUL!!

    The starter listed above has no markings that it has been tested by or passed any agency testing such U/L. I would NOT use or recommend an electrical product that has not be tested by an independent test laboratory. Things like that can start fires or worse.

    Tom

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    When I go to that link it doesn't take me to a product just tells me to use fewer words in the amazon search for better results. I came across a toggle switch much like what you would see mounted on a jointer or saw that is rated at 30 amps 230 volts 4 pin. I'm guessing from your response something like that won't work my question is why not? not robust enough for the application? Or are they only meant to handle that amount of current briefly? What I thought I was after was just a switch to connect the terminals something a bit more convenient then plugging and unplugging the motor every time i want to start or stop the lathe.

    I'm not doubting or arguing anything you have told me I'm just trying to learn. Thanks for all the help I appreciate it.

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    Quote Originally Posted by mega arc 5040dd View Post
    Would this simple 30amp 2 pole switch work? It's rated for the right amperage and voltage but it doesn't say anything about horse power but came up on amazon when I searched manual motor starter. I will admit I don't know much when it comes to motors and I may be over simplifying what it is I think I need and will work.

    Leviton 3032-2I 30 Amp, 120/277 Volt, Toggle Double-Pole AC Quiet Switch, Extra Heavy Duty Spec Grade, Self Grounding, Back and Side Wired (Ivory): Amazon.ca: Tools & Home Improvement
    Wow, that switch is a lot cheaper in the US.

    https://www.amazon.com/Leviton-3032-...NsaWNrPXRydWU=

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    The problem with a simple toggle switch is that it does not have to capability to interrupt an arc. These switches are meant for carrying the stated currents but not interrupting motor currents. If a motor stalls and you try to shut it off, all the stored energy in magnetic fields have to be dissipated in the break arc. Motor starters can do that without damage. Simple toggle switches cannot and may explode if called on to so.

    Do a Google search with the search term "toggle switches with horsepower ratings" and you will find references to several manufacturers that have toggle switches with hp ratings. Example, there others also.

    http://www.cooperindustries.com/cont.../AHBG-E-34.pdf

    Tom

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    That helps me to better understand what I need unfortunately it also is making it harder to find something for relatively cheap. Some motor starter switches are worth more than the motor. I am assuming the reset button on the motor is just for current overload and not for interrupting the arc.

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    Here's a toggle switch that supposedly can be used for motor switching.

    https://www.leviton.com/en/products/ms302-ds

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    I was just about to post that exact model of switch I found on amazon and ask if that would work. Its one of the few I found on amazon and ebay for a 5hp motor thats not going to brake the bank. I will call around tomorrow to some local electrical suppliers and see how their prices compare to online. Thanks to everyone for all the help.

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    That Leviton toggle switch IS rated for HP, but it's 2HP at 240V. You have a 5HP motor. No good...
    https://www.leviton.com/en/products/3032-2i

    That's why I said you CANNOT go by amps alone. Switching a motor on and off is not the same as switching a light on and off.

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    The Leviton switch we are talking about is MS303-DS and is rated for 5HP at 240Volts 30amps.

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    I suggest a drum switch (reversing). When threading it can be useful to back up the spindle to get to the beginning of the thread rather than messing with the half nuts.

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    Quote Originally Posted by mega arc 5040dd View Post
    The Leviton switch we are talking about is MS303-DS and is rated for 5HP at 240Volts 30amps.

    Yes, it does take care of the HP. That can be seen from the picture, although the Leviton spec page does not quote a HP rating. I assume, but do not know, that the picture is "actual" and not merely "representative".

    For the US (assume it is similar in Canada), on a 5 HP, it is required to use a "motor starter", which includes an overload. The switch has no overload in it, so that is (for the US) only a partial solution.

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    I know you're very knowledgeable about this stuff, but they do spec HP. And if you can't use them for motors, why do they market them for motor use?

    https://images.homedepot-static.com/...c898b6712b.pdf

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    Close to 40 years ago I was an interior trim sub-contractor. Not on any of my stuff, but I saw plenty table saws, etc. with regular house light wall switches for motor switching. It was very common. Not saying that was a good thing, just that it was prevalent because it was a cheap, easy fix if your switch went out.

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    OP says the motor has a 'reset button', so it likely has internal overload protection and separate protection isn't required.

    I'd be concerned about frequent start/stop on something as large as 5HP, though. Unless you're just using it for turning, the starting at each end of a thread is going to kill it fast.


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