I am replacing the motor on a whole house fan. The old one was 1/3HP 220V single phase. The new one is 1/3HP 220V split phase. Will the low, high and common connections be the same or is there different wiring for the split phase motor?

  • \$\begingroup\$ No difference. At a 1/3hp, odds are the original was a split phase. You need to do something to get motor spinning. \$\endgroup\$ – StainlessSteelRat Apr 7 '17 at 16:13
  • \$\begingroup\$ All single phase motors need some method of creating a delayed magnetic phase in addition to the main magnetic field, to force the motor to reliably start is a predictable direction. One possible difference might be if the new motor employed an external capacitor, to serve the start-direction function. Many split phase motors do, and many have the capacitor built in so you don't have to deal with it. But some split phase fan motors, like many I've seen on central AC units, have the capacitor separate, which would mean a little extra wiring, and placement for the capacitor. \$\endgroup\$ – Randy Apr 7 '17 at 17:49
  • \$\begingroup\$ @Randy If it has a capacitor, it's a capacitor-start (most likely) or a capacitor-run single-phase motor. \$\endgroup\$ – StainlessSteelRat Apr 7 '17 at 17:57
  • \$\begingroup\$ @StainlessTteelRat -- From Wikipedia google.com/search?q=split+phase+motor&ie=utf-8&oe=utf-8: "A capacitor start motor is a split-phase induction motor with a starting capacitor inserted in series with the startup winding..." \$\endgroup\$ – Randy Apr 8 '17 at 21:49

The term "single-phase" would apply to all types of single-phase motors, split-phase, shaded-pole, universal and others. If the motor is self-contained, there should be only two power connections, L1 and L2 or L1 and neutral. In addition, the motor housing should be connected to protective earth ground. If there are three power connections, the third connection would be for an external capacitor. If that is the case, you need to identify the capacitor rating and which connections it should be connected to. If you have purchased a motor that lacks that information, return it and buy a motor that has the proper information.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.