Slow Running AC Unit Seems Like It's Not Getting Full Power

Assuming the unit needs the neutral do not disconnect it. Even if it does not need the neutral, leave it alone, disconnecting it will not solve your problem.

Did using a meter show the receptacle had 240 volts?

Yes the outlet checks out at 220- 240. I was wondering it the neutral connected to the bus bar when there is no neutral on the outlet or the plug may have something to do with the lower running speed.

Was the unit working properly prior to installing the 30 amp breaker?

Why did you replace the existing breaker?

Did you replace a "Double Pole Breaker" with a Double Pole Breaker"?

This is a new breaker added for the AC unit, it originally had full power for a few minutes before it slowed down shortly after. I did use a multi meter and it shows 120 at each hot leg of the receptacle, I just thought the neutral might be the problem. But u did let me know that the neutral is not the problem so I guess i will keep checking for the cause.

Okay,

Neutral is only needed if the A/C unit needs to supply 120 volts for use by the A/C unit.

It is critical that we know what was the original circuit configuration made up of before we can really help you.

Just knowing that you have 240 volts between the hot conductors does not tell us whether or not you have an amperage problem.

What is the required amperage listed on the metal nameplate for the A/C?

Did you just replace the breaker or did you change the entire circuit from the Main panelboard through to the receptacle for the A/C?

For example, if you had a 20 amp breaker, you would normally have #12 AWG cable from the breaker to the receptacle.

However, since you put a 30 amp dual breaker into the circuit, you must us a #10 AWG (copper) cable. A #12 AWG cable will not be able to handle the heat and may cause the insulation on the conductor to melt and then the exposed conductor can and usually does cause a fire.

I have a 200 amp service in the house and a 200 amp sub panel outside. I have 100 amp double pole breaker outside which runs a welder. I added a 30 amp double pole breaker to the outside breaker box to run the AC unit and the wire is #10. The required amperage for the AC is 30 amps at 220/240 volts. This AC unit is 220 volts and its a new line that was run just for the AC unit from the 200 amp sub panel outside with a 30 amp 2 pole breaker. The sub panel has two hot lead connected to the breaker and a ground, it also has a neutral because that's the way the wire I bought came but the outlet and the receptacle only have two hots and the ground. The neutral is only connected at the sub panel not at the outlet or the receptacle because they are only three wires , 2 hots for the 220 and 1 ground wire.