Instruction manual

OM 751-4 18 www.DaikinApplied.com
desCrIptIon of operatIon
Cool Mode (Super State)
When in Cool mode the UVC uses primary cooling (economizer) and secondary cool-
ing (mechanical, DX) as needed to maintain the effective cooling set point (see "Space
Temperature Set Points" on page 25). The keypad/display or network connection
can be used to force the unit into the Cool mode. When the UVC is in Auto mode, it is
“normal” for the UVC to “idle” in Cool mode when there is no need to switch to another
mode. The Cool mode super state consists of the following UVC states: Econ Mech [1],
Mech [2], Econ [3], Cant Cool [12].
When the Cool mode super state becomes active, the UVC will automatically deter-
mine which UVC state to make active based upon the transitions for each state.
If the space temperature drops below EHS, and the Emergency Heat function is en-
abled, the UVC will be forced into the Emergency Heat mode (see "Emergency Heat
Mode (Super State)" on page 17).
Figure 10: Cool mode super state diagram
COOL
Mode
Enter from:
LUI Input
Network Input
Auto Mode
Economizer
available?
ECON
Mode
(State 3)
MECH COOL
Mode
(State 2)
Yes
No
OADP=100%
for > 3 min
ECON MECH
Mode
(State 1)
Yes
Are inputs
valid?
Return to
previous state
Continually
Check Input
IAT, DAT, OAT
Econ avail.
Mech cool avail.
Are inputs
valid?
CANT COOL
Mode
(State 12)
No
Continue in
current mode
Yes Yes
No
Econ State (State 3)
The Econ state is a “normal” state during Cool mode. The Econ state typically is active
in the Cool mode when primary cooling (economizer) is available and adequate to meet
the cooling requirements.
When the Econ state becomes active, the UVC will (within State) continually calcu-
late the DATS (“Discharge Air Temperature Control” on page 31) required to maintain
the effective cooling set point (see "Space Temperature Set Points" on page 29). The
calculated DATS will not be allowed to go below VCLL. The UVC will use economizer
cooling (see "Economizer Operation" on page 35) as needed to maintain the cur-
rent DATS. If the economizer position reaches 100% outside air and cannot satisfy the
DATS after a period of 3 minutes the unit will enter the Econ Mech State. If cooling is
not required while in the Econ state, the UVC can “idle” in the Econ state until cooling is
required or until there is a call to switch to another mode or state.