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Thread: Magnetic starter on a bandsaw?

  1. #1
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    Magnetic starter on a bandsaw?

    I have a dumb electrical question. I got my new Parks 18" bandsaw home last week and ordered urethane tires for it right away as the bottom tire is missing and the top is loose. In the meantime I have been wondering about the motor. It currently is set up with a magnetic starter to run on 230v. To my uneducated eye the motor looks like a completely normal type, and I am wondering if there's a reason why I can't run it on 115v with an ordinary 15 amp toggle switch or the like. The magnetic starter says it is rated for 1 hp at 230 and 1/3 hp at 115, max 9 amps. I would much rather run this saw on 115 since I have many plugs for that, and only a 50 amp 230 outlet in the corner, from whence I would have to run an extension cord. Thanks in advance for any advice about this.

  2. #2
    Yes, you can rewire that motor to run on 120V.

    Motor starters have the advantage of providing overload protection for the motor, and heavier contacts with faster make/break action to avoid degradation due to arcing associated with motor (inductive) loads. Magnetic starters also have the advantage that they turn off and stay off in the event of a power interruption (which is a useful safety feature).

    If you aren't worried about those features, you can remove the starter and replace with a switch. It would still be wise to select a "motor rated" toggle switch, not the cheapest contractor-grade light switch.

  3. #3
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    Thank you very much for your help. I will keep the "motor rated" idea in mind. I don't think I need to worry too much about power interruptions or overloading the motor, as I don't intend to use the saw heavily. I do need to do tall resawing occasionally, but never more than 2 or 3 feet at a time, and that only once a month or so.

  4. #4
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    Any chance it is a dual voltage coil? You would have to replace one or both heaters to make it work on lower voltages. My self I like the safety of a starter so I might find it cheaper to replace the guts inside the box. A starter like that allows for multiple stop start stations.
    I would buy a used starter. with a 120 volt coil on the bay with adjustable overloads for around $30 delivered.
    Bill D

    for an idea

    https://www.ebay.com/itm/40232089377...sAAOSwrlZfB4fm
    Last edited by Bill Dufour; 09-07-2021 at 5:23 PM.

  5. #5
    My 2 cents says leave it running on 230 v, it will run cooler and stronger. A three wire 12 guage cord will be fine for that saw out to 50 ft.No fuss no muss and a happier motor with no fiddling with rewiring.

  6. #6
    Quote Originally Posted by bill godber View Post
    My 2 cents says leave it running on 230 v, it will run cooler and stronger. A three wire 12 guage cord will be fine for that saw out to 50 ft.No fuss no muss and a happier motor with no fiddling with rewiring.
    The idea that a motor runs "cooler / better / stronger" on 240V is a bit of a myth. The motor, itself, sees the same voltage (once the wiring is configured). But at 120V, it draws twice the current, which can lead to more voltage drop in the circuit feeding it, which can potentially contribute to poorer performance if that voltage drop is excessive. A motor on a properly-sized 120V circuit will perform identically to one running at 240V.

    For a 1HP motor drawing 12A, it shouldn't be a problem.

    When folks find that a motor works "better" after switching to 240V, what they're generally saying is, "I had this plugged into a shared 120V circuit with 12 other loads. When I ran a short, dedicated, heavy-gauge 240V circuit, it worked better." Well...yes

  7. #7
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    I'll say this: When I run my Table Saw at 230V it runs stronger, spins up faster, and generally works better than when it was wired to run on 115V. This with the factory cordset on a dedicated outlet in both cases.
    Sharp solves all manner of problems.

  8. #8
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    I would listen to Bill's advice. It makes no sense to me to downgrade a perfectly good starter to a conventional switch. Take the starter to an
    electrical supply house with the picture of the motor tag and they should be able to switch out heaters if needed.

  9. #9
    Quote Originally Posted by Rob Luter View Post
    I'll say this: When I run my Table Saw at 230V it runs stronger, spins up faster, and generally works better than when it was wired to run on 115V. This with the factory cordset on a dedicated outlet in both cases.
    This would indicate you have some very interesting physics at play. If you look at the schematics of a motor wired for 115V or 230V, in both cases a given winding 'sees' the same voltage (115V in your case). So for a given load, the rpm is the same, the current is the same, the magnetic flux is the same, the torque is the same, and the horsepower is the same. ...Electrically speaking of course.

    Your saw is clearly not my saw, so will trust you have quantified this performance 'gain'. (Can I ask who makes it? I may need one too.)
    Last edited by Malcolm McLeod; 09-07-2021 at 9:52 AM. Reason: same situation for a saw converted from 120 to 240V

  10. #10
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    I would tie off that outlet and install a sub panel then run. 240 near where it is needed.. If you are running a saw, dust collector and maybe an air compressor or conditioner 120 volts is not going to do it with 25 amps.
    One horsepower is about the limit for 120 volts. For an 18" bandsaw you really need 1.5 Hp or more. Any plan to get a tablesaw? 50 amps is great for a welder. or car charger.
    Are you going to stay in the house or move?
    Bill D.
    Last edited by Bill Dufour; 09-07-2021 at 10:47 AM.

  11. #11
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    Quote Originally Posted by Malcolm McLeod View Post
    This would indicate you have some very interesting physics at play. If you look at the schematics of a motor wired for 115V or 230V, in both cases a given winding 'sees' the same voltage (115V in your case). So for a given load, the rpm is the same, the current is the same, the magnetic flux is the same, the torque is the same, and the horsepower is the same. ...Electrically speaking of course.

    Your saw is clearly not my saw, so will trust you have quantified this performance 'gain'. (Can I ask who makes it? I may need one too.)
    Ridgid TS3650. From the owner's manual

    "SPEED AND WIRING The no-load speed of this tool is approximately 3450 rpm. This speed is not constant and decreases under a load or with lower voltage. For voltage, the wiring in a shop is as important as the motor’s horsepower rating. A line intended only for lights cannot properly carry a power tool motor. Wire that is heavy enough for a short distance will be too light for a greater distance. A line that can support one power tool may not be able to support two or three tools."

    I ran the saw on 115 volts when I bought it. Due to what I'm sure were a number of factors (including the length of the branch circuit run) I experienced voltage drop under load that manifested itself as blade RPM reduction. Cutting 8/4 oak was a chore. It bogged the saw down. Rewiring to 230V decreased voltage drop under load and resulted in better performance. Did I measure this with full instrumentation? No. Did I measure torque under load at the motor shaft? No. It flat performs better. cutting 8/4 oak is no longer an issue. I'll withhold your comments from the saw, as it apparently believes the voltage change made a difference. I don't want it to think otherwise and start sand bagging.
    Sharp solves all manner of problems.

  12. #12
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    Thank you all for your advice. I don't currently have any 230v equipment in the shop, my big motors are 1.5 hp in the 18" Jet bandsaw and 10" Delta contractor's saw, and maybe the Shopsmith or the SuperMax drum sander, I can't recall what size the main motor is on those. I do have a 50 amp 230 volt plug in the shop, but don't use it. There is another of these in an outbuilding which runs the old stick welder when needed. I am planning to move next year. I know the area I want to go to but have not bought a house yet, so I don't know what the electrical situation or indeed the shop situation in general may be like in the short term after the move. I don't expect any trouble from running the 1 hp motor on the same circuits that run the 1.5 hp motors (of course not at the same time). I am only one person in the shop and only run one tool at a time. I will hang onto the magnetic starter for now, and if I find I want it I can hook it up to the motor again.

  13. #13
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    Quote Originally Posted by Bill Dufour View Post
    Any chance it is a dual voltage coil? You would have to replace one or both heaters to make it work on lower voltages. My self I like the safety of a starter so I might find it cheaper to replace the guts inside the box. A starter like that allows for multiple stop start stations.
    I would buy a used starter. with a 120 volt coil on the bay with adjustable overloads for around $30 delivered.
    Bill D

    for an idea

    https://www.ebay.com/itm/40232089377...sAAOSwrlZfB4fm
    The starter is not large enough for a 1HP motor at 120 volts, so no, you can't convert that starter to 120V operation for that machine.............Regards, Rod.

  14. #14
    Quote Originally Posted by Rob Luter View Post
    .. I experienced voltage drop under load ...
    With apologies to Mr. Hoyt for the diversion...

    Mr. Luter, perhaps we are stuck in a semantics trap here? I suspect you correctly ID'd the issue and it has nothing to do with the motor - tho' that is how this report of "improved performance on 230V" is so often phrased. If the motor is supplied with properly spec'd voltage (no matter if 115V or 230V), that motor WILL perform equally well with either voltage. Simple physics. I also suspect in the majority of home shops it is far easier to deliver 230V to the tool and keep it within spec as the tool is loaded (vs 115V). Builder grade 16ga wire, or 25' of 18ga 'lamp cord' extension at 115V in the average garage shop can savage the best laid plans - or tool.

    I saw a video recently of a neat little tester pair for household circuits that allowed the user to determine the physical order of wiring of duplex receptacles: which was closest to the breaker panel (1st), which was 2nd, 3rd, etc.. All based on voltage drop under 15A. applied load. IIRC, drop varied from ~6% to ~16%, within the space of 2 small bedrooms (....SWAG 20-25' of wire from 1st to last plug??). In this latter case, your saw would be roaring along on ~97V.

    To avoid this, I ran surface mount conduit with 12ga wire for all my 120V circuits in my current shop.

    (I know, I know ...120V and 240V are standards)

  15. #15
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    I love diversions, they're most of how life seems to go. I don't know much about things, so I am always happy to learn something new.

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