# 120/240 volt motor testing



## hydro (Aug 21, 2009)

I don't do a lot of work on motors but I have a 120/240 volt motor I believe to be 11/2hp with No nameplate. I need to figure out how to wire for 240 volt operation and I'm not to familiar with testing and what not. The motor has 7 leads thanks for the help


----------



## micromind (Aug 11, 2007)

If the leads are numbered P1, P2, T2, T3, T4, T5 & T8 and you want it to rotate clockwise with the shaft pointing away from you, then P1 is one of the 240 lines, cap P2, splice T2, T3 & T5, and T4 & T8 connect to the other 240 line. 

If it turns the wrong way, swap T5 & T8.


----------



## hydro (Aug 21, 2009)

Nothing is labeled the only way to figure it out would be to test the leads I know there is a way to do so I just can't remember how


----------



## hydro (Aug 21, 2009)

Nothing is labeled the only way to figure it out would be to test the leads I know there is a way to do so I just can't remember how


----------



## John Valdes (May 17, 2007)

Single phase starts on page 8. Hope this will help you. For sure you should be able to mark the leads.

http://www.goevans.com/filesSite/EHB_pgs0803.pdf


----------



## micromind (Aug 11, 2007)

This will be a bit more difficult since none of the leads are labeled........

There are 3 windings in this motor, two are identical run windings and the 3rd is the start winding. Since there are 7 leads, most likely the motor has a built-in O/L. 

First, we'll identify the run winding with one end connected to the O/L. The O/L involves P1, P2, and T1 (though T1 is connected internally). P1 to P2 will be VERY low resistance. P1 (or P2) to T2 will be a bit more resistance, depending on the basic design of the motor, I'd guess anywhere from 0.5Ω to 2Ω. 

T3 to T4 will be the same resistance as P1 to T2. 

T5 to T8 will be sort of open, because you're reading across the start capacitor. It may read open from the start, or it may have a reading that goes up for a few seconds then reads open. This is the meter charging the start capacitor. 

When you get the leads labeled, connect the motor for 230 volts as I described above, but apply 120 to it. If it runs, you got lucky on T3 & T4. If it just hums and doesn't turn, reverse T3 and T4. Polarity matters in motor windings. 

One issue here will be that there's no way to know P1 and P2. If P1 happens to be labeled properly, then the O/L will work. If power is applied to P2, the motor will run ok, but the O/L won't work. 

Once you get it to run on 120, go ahead and blast it with 240 and it'll run ok.

Edit to add; if the motor has sat unused for more than a couple of years, get the voltage and mfd ratings form the capacitor(s). Occasionally, capacitors have a bad habit of blowing up if left uncharged for a long time then suddenly hit with full voltage. If it blows, you won't be able to read the ratings and there's no standard of ratings for any given HP.


----------



## hydro (Aug 21, 2009)

Awesome guys thanks a lot I'll mess with it when I get back to the shop


----------

