Daikin MicroTech III Operation Manuals page 96

OA/EWT Lockout
Heating is disabled whenever the outdoor air temperature
is greater than the Outdoor Air Ambient Heating Lockout
Set Point . When the outdoor air temperature drops below
the Outdoor Air Ambient Heating Lockout Set Point by more
than the Heating Lockout Differential, heating operation is
re-enabled . Cooling is disabled if outdoor air temperature
or entering water temperature is too low for operation . The
outdoor air temperature becomes too low for operation when
it drops below the Outdoor Air Ambient Cooling Lockout
Set Point . Outdoor air temperature becomes high enough
for operation when it rises above the Outdoor Air Ambient
Cooling Lockout Set Point by more than the Cooling Lockout
Differential . The entering water temperature becomes too low
for operation when it drops below the Minimum Entering Water
Temperature Setpoint . Entering water temperature becomes
high enough for operation when it rises above the Minimum
Entering Water Temperature Setpoint by more the Cooling
Lockout Differential .
Tenant Override
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
OM 920-6 • MICROTECH UNIT CONTROLLER
Zero OA Time (Morning Warm-up)
A separate Morning Warm-up operating state is not provided,
but an editable 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 Optimal 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 .
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
for VFD) . 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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