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Thread: 240/480 volt question

  1. #1

    240/480 volt question

    Hi,
    I just scored a nice Northfield No. 2 18" planer. One issue is that it was wired for 480. I was able to rewire the motor leads from the high voltage to the lower voltage setting. The starter coil also has a diagram for low vs. high which was changed. Pressing the ON switch gave a hum, but manually engaging the contactor started the motor just fine. I took apart the on/off switch and cleaned all contacts and its better. It wants to start, but clicks and arcs quite a bit in the contactor. The on and off buttons do seem to work as they should. I am thinking that lowering the voltage (and increasing the amperage), is causing the arcing. One other item that is odd is that the on/off switch has a jumper between the no and nc terminals.

    I have attached pics of the coil, the on/off switch, and the full contactor assembly.

    I may have to get a motor guy on this, but hopefully i can at least be ready for them. Any ideas?
    thanks,
    Stevo
    Attached Images Attached Images

  2. #2
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    The coil look correct. I think the jumpers are stamped sheet metal. I do not see the power inputs. It should go to one or two and the other to three or four correct? No neutral involved.
    Bill D

  3. #3
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    I can understand how you can rewire a dual-voltage motor but I don't know how you would use the same motor starter. As you noted, the current will be double so you need a higher rating on both the contactor and overload. Shouldn't be too difficult to just replace the starter with one rated for your motor as wired.

  4. #4
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    Assuming it is three phase
    Comments made here are my own and, according to my children, do not reflect the opinions of any other person... anywhere, anytime.

  5. #5
    Quote Originally Posted by Charlie Velasquez View Post
    Assuming it is three phase
    It is three phase and the contactor does list both 240 and 480 voltages at least for amperages, so my guess is that the contactor should handle it, but obviously something is wired wrong, or maybe the contactor cant do it.
    Attached Images Attached Images

  6. #6
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    Of course the heaters will have to be replaced but it should pull in and close the contacts. It may be cheaper to buy a correctly sized used overload then to buy three new heaters.
    Bill D

  7. #7
    Quote Originally Posted by stevo wis View Post
    Hi,
    I just scored a nice Northfield No. 2 18" planer. One issue is that it was wired for 480. I was able to rewire the motor leads from the high voltage to the lower voltage setting. The starter coil also has a diagram for low vs. high which was changed. Pressing the ON switch gave a hum, but manually engaging the contactor started the motor just fine. I took apart the on/off switch and cleaned all contacts and its better. It wants to start, but clicks and arcs quite a bit in the contactor. The on and off buttons do seem to work as they should. I am thinking that lowering the voltage (and increasing the amperage), is causing the arcing. One other item that is odd is that the on/off switch has a jumper between the no and nc terminals.

    I have attached pics of the coil, the on/off switch, and the full contactor assembly.

    I may have to get a motor guy on this, but hopefully i can at least be ready for them. Any ideas?
    thanks,
    Stevo
    The clicking and arcing are probably due to insufficient magnetic force on the contactor - - the coil output is too weak. This is exactly what I would expect if the coil was wired with a voltage that is too low.

    Your computer screen capture of the coil label shows 2 jumpers (L & R) in place on the coil for 240V, and that is what that coil picture is wired for. If you were to wire it for 480V, then only 1 jumper would be 'center mounted'.

    In the first photo (full contactor), it is hard to tell for sure, but from my perspective it looks like the coil is still wired for 480V. You mentioned it was changed .... was the photo before or after the change? I'd double check this coil setup. (...Best I can offer from the photos.)

    ***
    Maybe this will better explain my misconscrewsion:
    2022-07-05_9-14-07.jpg
    Last edited by Malcolm McLeod; 07-05-2022 at 10:25 AM.

  8. #8
    Quote Originally Posted by Bill Dufour View Post
    The coil look correct. ...
    Sorry to disagree, but I just can't tell for sure.

    Quote Originally Posted by Bill Dufour View Post
    Of course the heaters will have to be replaced but it should pull in and close the contacts. It may be cheaper to buy a correctly sized used overload then to buy three new heaters.
    Bill D
    If the heaters were properly sized for the previous owner's resulting 480V current, then Mr. Dufour is exactly correct. But the fact that the unit hasn't tripped the O/L yet - on starting - may just possibly mean the O/L (heaters) were too big - - and may work at 240V? - - depending on how heavily you load the unit?

  9. #9
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    Quote Originally Posted by Malcolm McLeod View Post
    If the heaters were properly sized for the previous owner's resulting 480V current, then Mr. Dufour is exactly correct. But the fact that the unit hasn't tripped the O/L yet - on starting - may just possibly mean the O/L (heaters) were too big - - and may work at 240V? - - depending on how heavily you load the unit?
    How does one normally test that the overload is sized or adjusted correctly?

  10. #10
    Quote Originally Posted by Greg Funk View Post
    How does one normally test that the overload is sized or adjusted correctly?
    For most circuit interrupters, already installed in the field, there are electrical test specialists with suitably specialized equipment to perform these tests. All engineers that I've met, but I have forgotten the credential requirements. They basically use current amplifier coils (and low voltage) to inject current of sufficient magnitude and duration to cause a trip. (Last one I attended was part of new install of 4160V 4000A main CB and related MCC gear, fed from a Centaur turbine generator array on a offshore platform. I was validating the CB's interface to our automation systems.) The 'trip' felt like an earthquake! OK, a small one. 3.0

    The concept is exactly the same for heaters on a 240V 5Hp saw, but I'm guessing you might not want to go to this extreme ($$$).

    I would only suggest to the OP that he do what he's comfortable with, but if this system were mine, I'd buy new heaters of a known size/rating. They are not adjustable. And they have a memory: the more they are tripped, the lower and lower the trip point becomes.

    If I were 'in' on this machine for years to come, I'd pull the starter/overload, and replace with an IEC-format modular disconnect, starter, and adjustable O/L. To test the adjustable O/L, you drop the setting from the typical 1.4X or 1.5X FLA, down to the motor's FLA or slightly less. Then start the unit and let it run until it trips. This tests the actual safety trip function - but you still have to trust that the adjustment scale (dial) is accurate. In my experience, from a reputable supplier, their accuracy is certainly close enough to safely operate small motors (<10hp).

  11. #11
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    Quote Originally Posted by Malcolm McLeod View Post
    For most circuit interrupters, already installed in the field, there are electrical test specialists with suitably specialized equipment to perform these tests. All engineers that I've met, but I have forgotten the credential requirements. They basically use current amplifier coils (and low voltage) to inject current of sufficient magnitude and duration to cause a trip. (Last one I attended was part of new install of 4160V 4000A main CB and related MCC gear, fed from a Centaur turbine generator array on a offshore platform. I was validating the CB's interface to our automation systems.) The 'trip' felt like an earthquake! OK, a small one. 3.0

    The concept is exactly the same for heaters on a 240V 5Hp saw, but I'm guessing you might not want to go to this extreme ($$$).

    I would only suggest to the OP that he do what he's comfortable with, but if this system were mine, I'd buy new heaters of a known size/rating. They are not adjustable. And they have a memory: the more they are tripped, the lower and lower the trip point becomes.

    If I were 'in' on this machine for years to come, I'd pull the starter/overload, and replace with an IEC-format modular disconnect, starter, and adjustable O/L. To test the adjustable O/L, you drop the setting from the typical 1.4X or 1.5X FLA, down to the motor's FLA or slightly less. Then start the unit and let it run until it trips. This tests the actual safety trip function - but you still have to trust that the adjustment scale (dial) is accurate. In my experience, from a reputable supplier, their accuracy is certainly close enough to safely operate small motors (<10hp).
    Thanks for the info. I agree I'd just get a new starter. Likely less expensive than having a technician come out.

  12. #12
    Quote Originally Posted by Greg Funk View Post
    Thanks for the info. I agree I'd just get a new starter. Likely less expensive than having a technician come out.
    Malcom, Greg and the rest, I very much appreciate all the help, but I don't have it quite yet. I have attached another photo showing that the coil jumpers as they are now, which should be correct.

    I did talk with Northfield who verified that changing the jumpers on the coil and rewiring the motors for low voltage should be enough.
    He also said that only the red wire should be hot in the on/off switch shown above. tested the voltage on the red to ground and got 110, I also got 250v on the blue to ground.

    The on/off switch seems to work correctly and without any wires attached or the jumper on, the normally open and normally closed circuits seem correct. Once the wires are connected i get a closed circuit (start button, should be open?) between the black and the blue. The normally closed circuit (stop button), works correctly, closed until the stop button is pushed. I will call Northfield again and see about the hot blue wire and see if i can get a wiring diagram.
    I do have a friend with much more knowledge than i have, helping as well to be safe. It just seems like the switch or something below is wired wrong.

    When you say "heaters", are you talking about the three contacts that close and so replacing the contactor replaces the heaters?

    One last item there are two motors, the main cutterhead motor which if the starter is pushed manually does start and stay running until the stop switch is pushed.
    There is also the drive motor that runs the rollers and is reversible through a drum switch. I haven't gotten to that yet but will after the drive motor is correct. That is why there are two thermal protections below the contactor.

    The good news is I got a great price on it, the bearings seem fine, and it should be a great machine when finished.
    Thanks again for anything you have provided and any more suggestions.

    Stevo
    Attached Images Attached Images
    Last edited by Jim Becker; 07-06-2022 at 10:12 AM. Reason: fixed quote tagging

  13. #13
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    " I also got 250v on the blue to ground."

    For this to happen one of the other legs is grounded, find it before you get hurt.

    ron

  14. #14
    Quote Originally Posted by Ron Selzer View Post
    " I also got 250v on the blue to ground."

    For this to happen one of the other legs is grounded, find it before you get hurt.

    ron
    ^Agree.

    [QUOTE=stevo wis;3202447]
    Quote Originally Posted by Greg Funk View Post
    Thanks for the info. I agree I'd just get a new starter. Likely less expensive than having a technician come out.

    Malcom, Greg and the rest, I very much appreciate all the help, but I don't have it quite yet. I have attached another photo showing that the coil jumpers as they are now, which should be correct.

    I did talk with Northfield who verified that changing the jumpers on the coil and rewiring the motors for low voltage should be enough.
    He also said that only the red wire should be hot in the on/off switch shown above. tested the voltage on the red to ground and got 110, I also got 250v on the blue to ground.

    The on/off switch seems to work correctly and without any wires attached or the jumper on, the normally open and normally closed circuits seem correct. Once the wires are connected i get a closed circuit (start button, should be open?) between the black and the blue. The normally closed circuit (stop button), works correctly, closed until the stop button is pushed. I will call Northfield again and see about the hot blue wire and see if i can get a wiring diagram.
    I do have a friend with much more knowledge than i have, helping as well to be safe. It just seems like the switch or something below is wired wrong.

    When you say "heaters", are you talking about the three contacts that close and so replacing the contactor replaces the heaters?

    One last item there are two motors, the main cutterhead motor which if the starter is pushed manually does start and stay running until the stop switch is pushed.
    There is also the drive motor that runs the rollers and is reversible through a drum switch. I haven't gotten to that yet but will after the drive motor is correct. That is why there are two thermal protections below the contactor.

    The good news is I got a great price on it, the bearings seem fine, and it should be a great machine when finished.
    Thanks again for anything you have provided and any more suggestions.

    Stevo
    In the new photo, coil jumpers certainly look correct for 240V operation.

    As for heaters, they are bimetal elements that change shape as they heat up with high current - and so exert mechanical force to trip the circuit. This is a heater:
    2022-07-06_8-57-54.jpg

  15. #15
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    Quote Originally Posted by stevo wis View Post
    tested the voltage on the red to ground and got 110, I also got 250v on the blue to ground.
    Where are you getting your 3-phase power from? That combination shouldn't be available from any line to line or line to neutral combination. Locally, we have either 480/277 or 208/110 available from our utility. If you have similar you should see 208V between any combination of L1,L2 and L3

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