Okay, let's break this down. The key thing we're missing here is the specifications of the "MS302-DS" switch. Without knowing the switch's amperage and voltage ratings, we can't give a definitive answer. However, we can discuss the general principles and potential problems.

Why It's Complicated



Motor Starting Current

Motors draw significantly more current when starting up than they do while running at their rated load. This inrush current can be 3 to 7 times the running current. This is the biggest danger to the switch.

NEC (National Electrical Code) Requirements

The NEC has specific rules about motor circuits that are designed to handle this inrush current and protect the motor and the wiring. These rules often require overcurrent protection (breakers or fuses) and conductors sized larger than you might initially think.

Voltage Drop

The voltage drop along the wire can affect the motor performance.

Steps to Determine if the Switch is Suitable


Find the Switch's Specifications

The most important thing is to find the official specifications for the "MS302-DS" switch. Look for a datasheet from the manufacturer (e.g., Eaton, Square D, ABB). The datasheet MUST state:

Amperage Rating

This is the continuous current the switch is rated to handle. It may have different AC and DC current ratings. Also, many switches have general purpose rating and motor duty rating (hp rating).

Voltage Rating

The switch needs to be rated for the voltage of the motor circuit (typically 120V or 240V in a single-phase application).

Horsepower Rating

Some switches are rated for horsepower. If the switch has a 2 HP rating at the correct voltage, that's a good sign (but still check the amperage).2.

Determine the Motor's Full Load Amps (FLA)

The motor's nameplate will state its FLA. This is the current the motor draws when running at its rated horsepower and voltage.3.

Check NEC Requirements



Motor Overload Protection

Motors need overload protection, separate from the branch circuit breaker. This can be internal to the motor (some smaller motors have this) or provided by an external overload relay.

Branch Circuit Conductor Sizing

The NEC usually requires branch circuit conductors (the wires running to the motor) to be sized at least 125% of the motor's FLA. For a 2 HP motor at 240V, the FLA will probably be somewhere around 10-12 amps. 125% of 12 amps is 15 amps. #12 wire is rated for 20 amps and would be permissible.

Disconnecting Means

A switch used as a disconnecting means for a motor must be rated to interrupt the motor's locked-rotor current (LRC). The LRC is the very high current the motor draws when it's stalled. This is where the switch horsepower and/or amperage rating becomes critical.

Can You Use It with a 20A Breaker and #12 Wire? Possibly, but unlikely for 2 HP. A 20A breaker on #12 wire is a common residential circuit.

DANGER



Never use a switch that is not rated for the application. Overloading a switch can cause it to overheat, melt, and potentially start a fire. Never bypass or disable motor overload protection. This is crucial for preventing motor damage.

In summary, before you do anything

1. Find the data sheet for the "MS302-DS" switch.
2. Determine the motor's FLA.3. Make sure that the switch is rated for the motor's voltage and horsepower or the equivalent amperage. If it's not, you'll need a heavier-duty switch. If it's still not obvious if the switch is rated for motor duty, contact the switch manufacturer or a qualified electrician for advice.

I strongly recommend consulting with a licensed electrician. Motor circuits can be complex, and it's crucial to ensure the installation is safe and code-compliant. Flag for review