Daikin DPS Installation And Maintenance Manual page 99

Tenant Override
(See page 94 for more detail)
The tenant-override button provided with the optional zone
temperature sensor packages is used to override unoccupied
operation for a pre programmed time period . This time period is
set with the Tenant Override Time Increment . This value can be
adjusted from 0 to 300 minutes (default is 120 minutes) . When
an occupant presses and releases the tenant override button
on the zone temperature sensor (ZNT1), the Tenant Override
Timer is set equal to the Tenant Override Time Increment . (The
button must be held for at least 1 second but not more than 10
seconds .) The unit then starts and runs in the tenant override
mode which is the same as occupied mode except that it is
temporary .
The Tenant Override Timer begins timing out and the unit runs
until the timer expires . If the tenant override button is pressed
again while the unit is operating in tenant override mode, the
Tenant Override Timer is reset to the Tenant Override Time
Increment and the unit continues to operate . For example,
assume that the Tenant Override Time Increment is 120
minutes . One press of the override button provides at least
120 minutes of unit operation . If the button is pressed again
60 minutes later, the Tenant Override Timer is reset to 120
minutes, and a total of 180 minutes of uninterrupted operation
results .
NOTE: The same operation occurs if, instead of pressing the
override button on a zone temperature sensor, the
Occupancy Mode is set to "Tnt Ovrd . " Once set to "Tnt
Ovrd", the Occupancy Mode automatically reverts to
the "Auto" setting once the Tnt Ovrd Timer is set to
the Tnt Ovrd Time Increment . The same operation
will also occur if the network occupancy manual
command it set to bypass
Zero OA Time (Morning Warm-up)
A separate Morning Warm-up operating 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 . 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 Optimum Start is used ZeroOATime is set equal
to the time to occupancy when the unit starts so that the OA
dampers will open at occupancy time .
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Post Heat Operation
After leaving the Recirc or Heating operating state and entering
either the Fan Only or Min DAT operating state, the unit
performs "post heat" operation if the Post Heat Timer is set to
a non zero value . "Post heat" operation occurs within the Fan
Only or MinDAT operating state . During "post heat" operation,
the VAV Box Output remains open (heat) while the discharge
fan capacity is forced to a minimum value (default 33% speed) .
By forcing the discharge fan capacity to a minimum value
before the VAV Box Output closes (cool), "post heat" operation
is designed to prevent duct over-pressurization by decreasing
the duct pressure before the VAV boxes can close .
"Post heat" operation remains active until either the discharge
fan capacity reaches the minimum value or until the Post
Heat Timer expires, whichever occurs first. When "post heat"
operation ends, normal duct static pressure or position control
resumes .
NOTE: During "post heat" operation and for 120 seconds
afterward, the proof of airflow input is ignored. This
is to prevent nuisance Fan Fail fault alarms that may
occur if the airflow switch opens during or following
"post heat" operation . The unit cannot leave the Fan
Only or Min DAT operating state while the airflow
switch input is being ignored . The VAV output is only
available to the field via network communications.
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