Rewiring Power Tools for 240v

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  #1  
Old 06-13-01, 10:20 PM
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I am getting ready to purchase some Jet woodworking tools to replace ones which were damaged. The new tools (bandsaw and jointer) come prewired at 120v but are 240v capable. Since the ones they are replacing were 240v and I already have the dedicated outlets, I want to wire them for them 240v. The company I am buying them from has no clue and says the owners manuals, which do cover this topic, are very vague.

Does anyone have experience with this?

Is it difficult?

Procedure, please?

Any drawbacks to doing it vice switching my 240v outlets to 120v?

You time and input is greatly appreciated.

Be well,

Doc
 
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  #2  
Old 06-13-01, 10:55 PM
Wgoodrich
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When you are talking about machinery, you have an infinite abount of variations, from 120/240 single phase to multimotors that have both single phase and three phase, to machines that have multimotors both ac and dc on the same machine.

If you are dealing with simple machines with single or just a couple of motors, then check the name plate on all motors on that machine to say 120/240 and then check for two FLC ratings in amps one for higher voltage and one for the lower voltage. If the name plates of all motors on that machine says what is mentioned above then you can find the wiring designs to be change to adapt the voltage back and forth from 120 to 240 and back again on the name plate usually with a wiring diagram or take the cover off where the branch or feeder enters the motor and look on the back of that plate and you should find the same thing. Shouldn't be a big problem. Just changing a couple of wires over to empty spades. Just make sure your voltage, phase, FLC, and horse power matches what you had. One more thing for you to confirm is the rotation if your are just replacing motors. If you are replacing whole machines the rotation should not be a problem. If you motors say an odd voltage and / or say with 50 hertz then you probably will have to use a buck boost transformer for adapting that foriegn motor to our electrical systems.

If all you are changing is from 120 to 240 on a multivoltage rated motor it should take about 5 minutes to make the conversion.

Just make sure you got all the above confirmed.

Good Luck

Wg
 
  #3  
Old 06-14-01, 07:25 AM
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Wg, the power tools are single motor, single phase motors which do list 120v/14A or 240v/7A. Since I haven't bought them yet, can't take the plate off to check for the wiring diagram.

Question: The new plug and line, will it be 12/3 or 12/2? And if it's 12/2 how do I wire that since the outlets are all wired with 12/3? I've read where you do not use the neutral in this case (2-line 240).

Thanks,

Doc
 
  #4  
Old 06-14-01, 07:27 PM
Wgoodrich
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No neutral would be used if no lighting or other 120 volt equipment is running on that motor's power cord. Therefore you can just wire nut off the white wire in the receptacle box, change the receptacle to a receptacle that is amp rated to match the motor and designed for spades including two hot spades and one grounding spade in the receptacle design. You cord from the motor must match the amp rating of that motor and the plug should also meet that amp rating and matching that receptacle. In the future if you switch back to a 120 volt motor you would still have that white wire in that receptacle box to convert to the 120 volt motor without adding more wiring. By your amp rating as you said your cord can be 16 ga. if not over 6' in length and your breaker size in your panel should not be more than a 20 amp breaker in rating. Your branch circuit wire ampacity must be at least 14 Ga. but I would run or use 12 Ga. allowing for versitility considering future use in a commercial type setting.

You said that you can not look inside the motors. To convert a dual voltage motor you only move two wires inside where you install the cord serving that motor.

Make sure you rotation is correct and make sure your motor has T on the name plate designating this motor to be thermally protected. Most single phase motors are but a few are not, better to be safe than sorry on that subject. If you have a red button on the end of the motor built in to the motor then you would also be thermally protected.

Hope this helps

Wg
 
  #5  
Old 06-14-01, 08:28 PM
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Wg, that completely clarifies everything for me. I was pretty sure that I had it straight, just needed to verify it. Only question I have, and it'll have to wait until I get the drill press, is that it has a built in light. How can the drill press operate at 240 and the light at 120? Hopefully it's different wiring and I just pigtail the light onto the black and white wires and the motor onto the black and red (and the ground, of course).

The wiring for the cords, which I already have, is 14g and the supplying wire is 10g (I got a better deal to buy 10/3 than 12/3 - it was almost $25 cheaper - they said it was because the 250 foot boxed rolls were not selling - got it for $50). Oh well, works for me. The breaker is 20A (motor is rates at 15A). Yeah, could have used a 15A breaker, but, believe it or not, the 15A was twice the cost of the 20A - go figure. Home depot can be weird at times.

Anyway, I'm rambling now...lol...thanks for all the advice.

Be well,

Doc
 
  #6  
Old 06-14-01, 08:52 PM
Wgoodrich
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Quite often lights on a machine wired for 240 volt also have 240 volt bulbs. Check your machines and their light bulbs, this may be what you have. They often look the same as 120 volt bulbs, but they would be marked as 240 volt bulbs if that is their ratings.

Be careful using that 10 ga. wiring to 15 or 20 amp rated receptacles. If you run 10 ga. with intent to connect to 15 or 20 amp rated receptacles then you must pigtail a 12 ga or 14 ga. wire reducing that 10 ga. to the conductor that is rated for that receptacle. 15 and 20 amp receptacles are not designed nor approved to be connected to 10 ga. wire. Just install breakers in the panel to equal the maximum ampacity of the smallest conductor on the circuit, including these pigtails and devices.

Good Luck

Wg
 
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