HP rp7400 Manual page 29

Define E-Stop Requirements
The computer system power panel should include a shunt-trip wired to
an emergency shut-off switch and a thermostat device. Electrical codes
commonly stipulate that this button will remove both power AND airflow
from the computer room. This is for deactivating all equipment power in
case of an emergency or in case room temperature exceeds safe operating
conditions.
Check the local electrical codes to see whether the E-stop switch is
optional or required.
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