Emerson electric motor wiring?

[Todd Adornato]

I recently acquired an Emerson 1/30 hp electric motor that came with four wires coming out of the housing, with the exposed ends of each pair twisted together.  The seller didn’t know anything about it other than to say it worked when power was applied.  I labeled the four wires 1-4; 1 and 2 were joined, and 3 and 4 were joined.  2 & 4 are thicker than 1 & 3.  I tested for resistance between them all, with the following results:

1 - 2 = nothing

1 - 3 = 28.0 ohms

1 - 4 = nothing

2 - 3 = nothing

2 - 4 = 16.5 ohms

3 - 4 = 44.3 ohms

I applied 110 VAC power to the pairs 1 & 2 and 3 & 4 as they came to me, and the motor ran smoothly.

Why would there be four wires?  If there’s a switch involved, wouldn’t there be three wires coming out of the motor like on the big Emerson fans?  Is 1/30 hp really one-thirtieth of a hp as indicated on the motor tag?  It’s a big, heavy unit for such a low output.  Finally, does anyone have a wiring diagram for this motor?  I’ve attached a picture of the motor showing how the wires were joined.  Thanks for looking!

 

[Mark Olson]

The motor can be reversed.

When you apply power to (your label numbers) pair 1 & 2 and pair 3 & 4 the motor will turn in one direction.

If you apply power to pair 1 & 4 and pair 2 & 3 the motor will turn in the opposite direction

BTW, the ohm readings add up okay, but there is an error in your measurements. if you read between 3 & 4, then 1 & 2 were connected when you took the reading!

There probably should be a choke or capacitor on the start winding, pay close attention to RLA during operation without choke.

[Todd Adornato]

Mark, thanks for the comments.  I actually took the readings with all four wires disconnected from each other.  In a real-world setup, how would the four wires be routed?  Would there typically be a switch that allows for the motor direction to be reversed?  I’m curious as to what these motors were usually used for. 

[Mark Olson]

Yes, a double pole double throw switch would be used to reverse the motor.

I do not know what the intended purpose of that particular motor was.