Switchboard Insulation Resistance Chart

Always use a 500 or 1,000 Vdc megohmmeter when testing insulation resistance.

NOTE: The Neutral–Ground column in the table below is provided to record the results of the pre-energizing checkout procedure only.

DANGER
HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH Turn off all power to the switchboard before testing. Always use a properly rated voltage sensing device to confirm power is off. Failure to follow these instructions will result in death or serious injury.

CAUTION
HAZARD OF OVERVOLTAGE TO CONTROL AND PROTECTION COMPONENTS Remove the long-time rating plug before electrical insulation testing a circuit breaker that has a label stating “Warning: Disconnect Plug Before Dielectric Test.” Some MicroLogic trip units are not rated for voltages that would occur during electrical resistance insulation testing. Open all control and metering disconnects from the control circuits. Failure to follow these instructions can result in personal injury or equipment damage.

CAUTION

HAZARD OF OVERVOLTAGE TO CONTROL AND PROTECTION COMPONENTS

Remove the long-time rating plug before electrical insulation testing a circuit breaker that has a label stating “Warning: Disconnect Plug Before Dielectric Test.”
Some MicroLogic trip units are not rated for voltages that would occur during electrical resistance insulation testing.
Open all control and metering disconnects from the control circuits.

Failure to follow these instructions can result in personal injury or equipment damage.