230v Switch: Buzzing Sound When Pressing the Start Button

Created by Gabriel Izzo, Modified on Sat, 6 Apr at 9:38 PM by Gabriel Izzo

**Voltages and standards referenced apply to North American machines ONLY. Consult with a licensed electrician**

A noisy contactor typically implicates a voltage or amperage issue at the power source. 

The most common cause of this is the wrong circuit breaker being installed i.e. single pole instead of double-pole, or one of the power supply wires, typically the white wire if the outlet had been wired for 115v previously, may not have been converted from a neutral wire at the panel to a hot wire so the machine is trying to start with only half of the needed voltage. Instead of having two hot wires delivering 115v each for a total of 230v, only one of the wires is delivering 115v so the coil inside the contactor never reaches the needed voltage to engage so it may display symptoms of chattering, humming or buzzing inside the switch and failure to start.

To fix this, please verify the following:

  1. The machine is on a dedicated 240v-20A circuit with a 240v double-pole circuit breaker.
  2. The receptacle installed is a NEMA 6-20R receptacle to be used with the 6-20P plug on the machine.
  3. The receptacle is delivering 110v-120v on each hot leg for a total of 220-240v.
  4. The ground wire connection is properly grounded. 
  5. If there is a circuit breaker located on the switch, check that it is not tripped. If so, reset it, and try starting the equipment again. 

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