iWorx® HPU3
18
505-035, Effective: June 30, 2015
© 2015 Taco Electronic Solutions, Inc.
Cooling Sequence
The reversing valve and compressor stages are sequenced based on the space temperature and the calculated cool-
ing setpoint. When the space temperature rises above the calculated cooling setpoint, the reversing valve is cycled to
the cooling position. When the space temperature rises above the calculated cooling setpoint plus the cooling control
band for a predefined time period, a compressor stage is turned on. If the space temperature remains above the cool-
ing control band for an additional time period, the next available stage will be turned on. This cycle continues until all
available stages have been energized.
After the space temperature has dropped below the cooling setpoint for a predefined time period, the last-energized
stage is turned off. (Note that the last stage that was turned on will be the first one to be turned off.) If the space tem-
perature remains below the cooling setpoint for an additional time-period, the next previous stage will be turned off.
This cycle continues until all stages have been de-energized.
The configurable value "stage time" determines the duration of the stage. An absolute minimum stage ON time of 2
minutes, and an absolute minimum stage OFF time of 5 minutes are enforced when the space temperature is more
than the space setpoint. If the temperature falls below the space setpoint then the minimum on and off times are
ignored.
When the space temperature drops below the space setpoint, all of the compressor stages turn off immediately; the
stage time and minimum on time are ignored.
During unoccupied periods, the cooling setpoint is adjusted upwards through a separate unoccupied cooling setpoint.
