Operator's Guide; Determining Unit State; Off Operating State; Start Up Operating State - Daikin MicroTech III Operation Manuals

The following "Operator's Guide" sections provide information
regarding the day-to-day operation of the MicroTech III
Unit Controller . Topics covered are such common tasks as
scheduling, displaying and clearing alarms, and setting the
controller for manual operation .
Figure 11: State Diagram
The transition from any operating state to another is graphically
represented in this figure. With a "start up" command from an
OFF State the unit will always go into the "Start Up" state of
operation for 3 minutes (adjustable). Next, it will transition into
the "Recirculation" state of operation for another 3 minutes
(adjustable) before finally going into the Fan Only state of
operation . Then, based on sensor inputs it will go into any
of the 4 remaining states of operation - heating, cooling,
economizer, or minimum discharge air heating .

Determining Unit State

The unit will operate in one of eight operating states . The
current state will be displayed by the Unit State parameter in
the system summary menu .
In the OFF state, all heating, cooling, and fans are OFF . The
alarm output indicates the type of alarm, if any, that is active .
In the start up state, the Fan Operation output is turned ON to
allow shut OFF dampers to be opened before any the supply
fan is turned ON . The outdoor air dampers remain closed .
OM 920-6 • MICROTECH UNIT CONTROLLER
The supply fan is turned ON when the unit enters the
Recirculation state . The supply fan in VAV units is controlled as
described in the Supply Fan Capacity Control (VAV) on page
136 . The outdoor dampers remain closed .
A separate morning warm-up state is not provided, but an
edited ZeroOATime is used to keep the outside air damper
closed when the unit first starts. The Minimum OA Position is
set to zero as long as the as the fan has been on for less than
the ZeroOATime .
DAT Control units have a MWU setpoint available .
The Minimum OA Position is set to zero as long as the as the
fan has been on for less than the ZeroOATime . This allows the
Return Air type units to cool down the space with mechanical
cooling or to warm up the space with the dampers closed . If the
ZeroOATime is set correctly, the OA dampers will be open only
during occupied periods . When Optimal Start is used Zero OA
Time is set equal to the time to occupancy when the unit starts
so that the OA dampers will open at occupancy time .
Neither heating nor cooling is provided when the unit is in the
fan only state, with the exception of when dehumidification
is active . The outdoor dampers are opened to the minimum
position in this state when the fan on time exceeds the Zero
OA Time .
In the other four states, temperature is controlled as describe
in the appropriate sections of this document . These states are
Minimum DAT, Heating, Economizer, and Cooling . The outdoor
dampers are opened to at least the minimum position in these
states when the fan on time exceeds the Zero OA Time .

OFF Operating State

In the Off operating state the fans are off, the outside air
dampers are closed and any VFD's are driven to 0% . Cooling
and heating are disabled . The unit is in the off state when it is
not enabled, or when it is in the unoccupied mode with no call
for unoccupied operation . refer to "Determining Unit Status" on
page 70 for reasons the unit can be disabled .

Start Up Operating State

When a unit is commanded to start it will always enter the
Startup operating state from the OFF operating state . The unit
remains in the Startup operating state for an adjustable time
period (default 180 seconds) before entering the Recirculating
operating state .
During the Start up operating state the fans remain OFF, the
outdoor air dampers are driven closed, and VFD's remain at
0% . Cooling and heating are disabled, except for 100% OA
heating start sequences .
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