Should Ac/Dc Power Supplies Be Grounded?

Many Ac/Dc power supply manufacturers are not grounding the Dc side of their power supplies. In some cases, the Ac/Dc power supply manufacturer does not offer an option to even ground the Dc side of the power supply. The Ac side of the Ac/Dc power supply is required to be grounded via the NEC.

SPGS believes that the Ac/Dc power supply manufacturers are relying on the NEC Code article 250.162 that only requires Dc system supplying premises wiring and operating at greater than 60 volts but not greater than 300 volts shall be grounded.

Reasons that the Ac/Dc power supply Dc power should be grounded.

• It gives the hot side of the Dc power a designed path to trip the circuit breaker when the Dc hot wire becomes faulted.
• It equalized the Dc power to the facility grounding system.
  • When any equipment is not reference to a common grounding reference point during a power surge or lightning event typically will be damaged from the voltage event.
• It creates a common ground reference point for ground signals.
• It helps reduce common mode noise within the facility.

SPGS’s recommends to ground all Dc power supplied from Ac/Dc power supplies.