230v Switch: Buzzing Sound When Pressing the Start Button

**Important Electrical Information (North American Machines Only)**
Voltages and standards referenced below apply only to North American machines. Please consult with a licensed electrician before proceeding.

Noisy Contactor Diagnosis

If your machine’s contactor is making a chattering, humming, or buzzing sound and fails to start, it is most likely due to an incomplete or improper power supply.

Most Common Cause

The most frequent issue is either:

• An incorrect circuit breaker installed (e.g., single-pole instead of double-pole), or

• One of the hot wires (commonly the white wire) was not converted from neutral to hot at the panel, especially if the outlet was previously wired for 115V.

This results in only one hot leg supplying 115V, rather than two hot legs supplying a full 230V, which prevents the contactor coil from receiving enough voltage to engage.

How to Fix It

Please verify the following with a licensed electrician:

1. Circuit

   • Machine is connected to a dedicated 240V / 20A circuit.

   • A 240V double-pole breaker is installed (not single-pole).

2. Receptacle

   • A NEMA 6-20R receptacle is installed to match the 6-20P plug on the machine.

3. Voltage Test

   • The receptacle delivers 110–120V on each hot leg, for a total of 220–240V across both.

4. Grounding

   • The ground wire is securely connected and properly grounded.

5. Machine Circuit Breaker (if applicable)

   • Check the built-in breaker on the machine’s switch. If tripped, reset it and attempt to start the machine again.

Contact our Technical Support for further assistance using the following link:

Submit a Technical Support Ticket