# Trying to understand this electrical diagram schematic on an AC motor that I have, particularly symbol between yellow and black wires

I'm new to electrical wiring and I'm trying to learn a bit and came across this AC motor which I have that isn't hooked up. I have attached the motor wiring diagram:

This is also the wiring connection at the end:

I'm trying to make sense of this all and would appreciate any input, here is my understanding on the wiring:

1. Line wires are Red, Yellow, and Black? I don't understand the symbol used between the Yellow and Black wires in the diagram.
2. White is neutral?
3. Green is ground
4. The circle symbol between Red and yellow indicate they are both connected to line
5. White appears to be connected to blue? is this correct?

Using this diagram, if I connected an AC power cord with hot going to red, ground going to ground, and white going to neutral, would I be able to supply power? I'm guessing the other colored wires may be different motor speeds and I could supply / switch power to the other wires for different speeds?

I know I am probably wrong in a lot of this so any explanation or if someone wants to point me in a direction where I can learn more about things like this I would appreciate it.

Thank You.

• 1. Is there a centrifugal switch in it by any chance? Can you spin it up and listen for a click? Or see it mechanically? Commented Jan 28, 2022 at 17:21
• Could it be a thermal overload switch? Commented Jan 28, 2022 at 17:53
• That looks more like a thermal switch symbol. Commented Jan 28, 2022 at 18:06
• symbol between yellow and black wires ... that symbol is on the black wire ... it is between blue and yellow wires Commented Jan 28, 2022 at 18:34

The motor has a split stator coil that allows for 120V or 240V connection.

• The black wire is a mains lead, and has a thermal overload switch on it (the weird symbol on the third wire down.)

• The red, blue, yellow and white wires connect to split coils, and are to be connected to each other and the other mains lead as shown on the diagrams for 120 or 240V line.

• Green is ground, and it’s not on the connector, so I’ll assume it’s a separate bonded connection.

There is no ‘neutral’ wire per se on this connector, only two line-in wires. Further, the split coil lead colors don’t correspond directly to electrical wiring conventions.

Don’t infer that the white wire on the connector is neutral - it isn’t. It is never connected directly to a line, only to another coil by jumper.

For your testing, connect the jumper wires as shown first, as appropriate for your voltage. Then connect your line supply. This is best accomplished using a ‘pigtail’ mating connector that plugs into the motor’s connector. If you’re lucky the motor came with one, otherwise obtain one from a supplier first.

Here's how that looks:

simulate this circuit – Schematic created using CircuitLab

The upper two diagrams show line feed colors that you'll find in a 120V country: black = hot, white = neutral, red = hot. Lower diagram is for 240V countries like the UK and most of the EU, which use brown = hot and blue = neutral.

As to what's inside the motor itself, it's a capacitor-run motor that always uses 120V for the phasing coil. Here's what that looks like:

simulate this circuit

• thank you for this very detailed explanation. Commented Feb 1, 2022 at 21:13

That symbols should be an internal thermal switch, over-temperature protection. Wiring depends on voltage supply. In case 120 V, one line is connected to red&yellow, and another line to black (thermal switch), blue connected to white (jumper of windings). Green to ground.

• thanks for your explanation. regarding providing ac power to this motor for testing, can I wire the red and black to hot? Would I connect neutral to white / blue, green to ground to test the motor? Commented Jan 28, 2022 at 18:19
• It doesn´t matter if you connect hot or neutral to any line, that is hot=one of motor line (red and yellow wires) and neutral to other line (black). Join white and blue but don´t connect to grid, it is a jumper of the 2 windings. Commented Jan 28, 2022 at 18:31
• See diagram for your clarification. Commented Jan 28, 2022 at 19:00
• Diagrams have the colors mixed up. All color names refer to the line below the name.
– user80875
Commented Jan 28, 2022 at 19:05
• @Charles Cowie: Sorry, I don´t see the mistake. If you sure, I will delete it, not to confuse more. Commented Jan 28, 2022 at 19:16

So the symbol on there is a thermal overload on the black wire which is one of your incoming lines, red is the other line wire. White, yellow, and blue are just field wires for your field windings in your motor. For 120V yellow and red are together while white and blue of your field windings are in series, 240V blue and yellow are in series while white is not in the circuit.

The internal connections are shown below. Power is connected to Red and Black. For the 120-volt parallel winding connection, Yellow is connected to Red and White is connected to Blue. For the 240-volt series winding connection, Yellow is Connected to Blue and there is no external connection to White because it is already internally connected to Black through the thermal protection.

In addition to what is shown, a there is another winding and a capacitor connection that is not shown. Unless there is another wire or pair of wires coming out of the motor, the capacitor and its connections must be inside the motor.