You are here:

Electric Motors/Single phase dual voltage wiring.


I have been given a single phase motor, dual voltage 2hp, but no wiring diagram. It has 6 terminals numbered 1, 2, 3, 4, 5, and 6. 1&3 have a jumper, 2&4 have a jumper. It does have a capacitor. 1 through 4 have black wires going into the motor. 5 and 6 have red.

Most likely  1-3 is line   2-4 is line    red wires are some sort of thermal protector with an ohm meter we could tell exactly

      1-2-3-4 should be the motor leads,   slight chance the red wires are the start circuit,    if so   one each would go  to   1-3  and 2-4   which are parallel or low voltage connected

     so it should be 115/230   and 115 would go to 1-3,   then 2-4      if the reds are a winding which I doubt   one each to lines

     or the red wires could be the cap wires,   hard to say with no data,

   but it is odd   normally no one uses red for a winding    but for a thermal would be somewhat normal,          

you say capacitor but not if it is wired or just with the motor,   and what kind of cap, is it in a metal can or a plastic canister?

If it is plastic and has a rating like 365 it is a start cap,   if it is metal probably silver it is a run cap and would have a rating like 5, 7.5, or something down in that value  

Can you send photos of the wires coming out, or get an ohm meter?

The high voltage connection would be line to 1,  and line to 4   with 2-3 electrically connected and taped up as a series jumper,   

But that would mean the reds [if start winding] would have to be connected to one line and the 2-3 jumper to keep it at 115 volts or low volts

Whatever the rating is   low or high  not important exactly what  should be 115\230  110/220  so on    one twice the other,       

Motors are not all common duty motors   like you buy off the shelf somewhere,

  many are made for a specific device and they do all kinds of things,  but to color up windings would be very OEM     

If you can get an ohm meter  I need you to take a photo so you can get it back as it was,   

and if you get an ohm meter I will tell you what to measure then we can narrow down the windings by ohms,     and get much closer,    

For now  I would wire nut reds each,      put 110 on 1-3   and 2-4   see if you get rotation or it might take off,

but if there is a cap  but you dont say if it is connected or not,

 if the cap is wired    then try the wire nuts on reds

  line wired as directed above to 1-3   and then 2-4   it should hum if the red is the start,

might take off with a shove but be damn careful  if it does and has a keyway it will eat your finger      so try but best to wrap a string and pull it, if possible in both directions

or give it a spin prior to wiring the last power line  connect one hard with a nut,   expose the other  and touch the other line to it,  it might spark no problem   but be careful that way too    no good way to do this so be careful  either way  or not at all if you are concerned         

    then put the reds on the lines and if takes off it is the start circuit,    but without an ohm meter it is the best guessing I can do,

if it takes off with the reds on line   reversing the reds from line to line should change rotation, but I doubt it is a winding    if it is thermal the ohm reading could be really low almost nothing or like a short,  but hard to tell how they connected in the motor itself,     

measuring the windings   1-3 are now connected     so the circuits should be 1 to 2  and 3 to 4   

sometimes they use 1 to 3   and    2 to 4   that is just the WIRE and each set is half the winding and should measure in ohms almost exactly    if not it is shorted    also put the lead on the 1234   and one lead to the case where you find bare metal or scrap it with a file  

if the windings leads 1234  show a circuit to the frame the motor is grounded  do not use  it can be grounded and not "shorted"  or it could be shorted and not grounded  or both  either way   anything from winding to frame   stop   !!!!!!!!!!!!!!

send me photos or ohm readings or tell me you have a meter and we go from there

let me know  

Electric Motors

All Answers

Answers by Expert:

Ask Experts




Three phase/ AC DC single phase motors, controls, any problems or failures, motor installation, performance issues, connections. All other electric motors/gearboxes/apparatus. Specialty repair concerns, obsolete motors and solutions. Other mechanical or specialty equipment. See my profile under Home/electrical at this site


30 plus years in the electrical motor and apparatus repair industry. VP level management of repair facilities, current owner of my own specialty repair and consulting firm.

EASA, IBEW [retired], other specialty organizations, Lubrication, Vibration EDI, Tribo-electric Councils

Currently fielding concerns at this site under "Home Electrical"

4 year technical, College level specific courses, EASA repair courses, vibration analysis electronic and electrical trade school.

©2017 All rights reserved.