Honeywell HX2 Reference Manual page 164

Because of the cumulative effect, and using the Battery Power Scheme Defaults listed above:
The backlight turns off after 3 seconds of no activity,
l
The display turns off after 18 seconds of no activity (15 sec + 3 sec),
l
And the device enters Suspend after 5 minutes and 18 seconds of no activity.
l
If the User Idle timer is set to Never, the power scheme timers never place the device in User Idle, System Idle or Suspend
modes.
4-122