Help motor drawing to many amps

[Jimmy Noskowiak]

I'm in the process of changing my smci from three phase to single. I have a new 6 hp marathon and a new mag switch from grizzly. The motor is 25 amp and the switch also is for 25 amps. I'm getting 120v on both lines to both sides of the switch and to the motor. But the motor is drawing 60 amp on one of the feed lines and nothing on the other, so the switch keeps blowing after a few minutes. This is the second motor and both have done this. Could both motors have something wrong or is there something else that I maybe missing. Could the switch be screwing up? Any help would be greatly appreciated. Thanks.

[Dennis Ford]

It sounds like a wiring problem. You should have 240v to a motor of this size. I think you should get some qualified help to trouble-shoot your hook-up.

[Steve Jenkins]

make sure that you are getting 240 between the leads going to the motor.you may somehow have both leads coming from the same leg off your panel. this will give you 120 to ground off each but not 240 between them. It should be supplied by a 2 pole breaker.

[Jimmy Noskowiak]

Yes I do have 240 going to the motor. 120 on each line.

[Stephen Cherry]

Pictures? Do you have an ohm meter to measure the ohms across the two hot lines, and also from each hot to ground?

What you are describing is basicly impossible- 60 amps in one side and 0 on the other side (http://en.wikipedia.org/wiki/Kirchhoff%27s_circuit_laws)

So, the juice must be going somewhere else. Current on the ground line? do you have a wiring diagram for the motor? Is the start cap switching out?

[glenn bradley]

Yes I do have 240 going to the motor. 120 on each line.

And confirmed from two different legs?

[Ken Fitzgerald]

Jimmy........As asked by Glenn.....Have you measured between the two hot legs? If the motor is designed to function off of 240vac, it matters not that you measure 120 to ground or neutal on each leg but rather what you measure from 1 hot leg to the other hot leg. Measuring voltage between the 2 hot legs should result in a measured voltage of approximately 240 vac.

[Don Jarvie]

1st check the lines from the wall, 120 each leg and the ground and make sure these are wired right. then wire then to the motor directly and see if it works. if it does then the switch is the issue. Then you can make sure the switch is wired correctly. If you are running a 25 amp motor you should be using a 30 amp double breaker and 10g cord.

From what you describe the switch sounds like the issue.

[Mike Henderson]

When measuring voltage on a 240V circuit, always check across the two hot legs, not each hot to ground. You should have 240V across the two hots.

Mike

[Jimmy Noskowiak]

I think it may be the switch. I was doing some checking. When I was checking the volts and following the lines across the switch in the off position, one had 120v and the other only had 75v. I'm not a electrition but I think they should be the same. So I am thinking of sending it back. It's the only thing left.

[Don Jarvie]

What type of switch was on there before? You may want to hunt the Bay to find the same brand but one that can handle 25 amps on a single phase.

If you want to post the name and specs one of us maybe able to help point you in the right direction.