When the requirements of an HVAC system are examined over a time
period, the plant often displays a varied load profile. There
may even be periods when there is no real need for the operation
of a HVAC system, or time periods where the requirement to a fan
or a pump is so low that actual operation is will not impact the
To save energy during these periods, the
"Sleep Mode" feature has been introduced to the VLT®
6000 HVAC drive.
The VLT® 6000 HVAC drive is programmed to a sleep
frequency usually equal to the minimum motor speed desired by
the user. When the motor has been running at this frequency for
a specific (programmable) time period, the drive enters
"sleep mode" and the power to the motor will be
When "sleep mode" is in operation, the
drive will continue monitoring the system. When the systems
setpoint is no longer satisfied, power to the motor will be
turned on again.
The sleep and wake inputs to the drive are both
frequencies to enable this function to work in both open loop
and closed loop modes.