Temperature Control Configurations; Heat/Cool Changeover - Daikin MicroTech III Operation Manuals

One Event Scheduling
A One-Event Schedule is provided so that one operating
period can be scheduled without affecting the regular internal
schedule . A start date/time and an end date/time can be set .
The unit can be scheduled to operate during a specified period
by using this feature. During the specified period defined by
the One Event Beginning Date/Time and One Event Ending
Date/Time parameters the unit starts up and runs continuously
regardless of any other time scheduling functions . For
example, assume that a space served by the unit is occupied
for a special event on March 12, 2008 from 5:00 p .m . to 10:00
p .m . when the normal time scheduling has the unit shut off
after 4:00 p .m . on that date . This event can be accounted for
by setting the One Event Beginning Date/Time to "3/12/08 @
17:00:00" and the One Event Ending Date/Time to "3/12/08 @
22:00:00 ."
Optimal Start
When Optimal Start is active (Optimal Start = Yes), an early
start time is determined before each scheduled start . The
schedule must be based on an internal schedule or a signal
via a connected network that indicates time to occupancy . The
controller uses start history, outdoor air temperature and space
temperature to determine when the unit should start . The unit
may start up to four hours before the scheduled occupancy
time . Optimal start based on heating operates when the space
temperature is below the Occupied or Unoccupied Heating Spt
by ½ the Zone Htg Deadband . Optimal start based on cooling
operates when the space temperature is above the Occupied
or Unoccupied Cooling Spt by ½ the Cooling Deadband . If
space temperature is between the above two points, the unit
starts at the occupancy time .
External Time Scheduling
An external time clock can be used to schedule unit operation .
This is accomplished by a field supplied external time clock
signal in the form of a set of dry contacts wired across
terminals 101 and 102 on the unit field terminal block TB2. In
this case, all internal daily schedules should be set to "HH:MM-
HH:MM" (default setting) .
OM 920-6 • MICROTECH UNIT CONTROLLER

Temperature Control Configurations

Temperature control is based on a Control Type that may be
set to Zone, DAT, or Single Zone VAV .
When the Control Type is set to Zone temperature control,
heating, compressors, and the economizer are controlled to
maintain the temperature of the zone at a desired setpoint .
This configuration is used on units equipped with constant
volume supply fans . Compressors and heating stages are
staged to maintain space or return temperature . The number
of compressors is decreased when it is too cold and increased
when it is too hot subject to stage timers. The number of heat
stages is decreased when it is too hot and increased when it is
too cold subject to stage timers.
When the Control Type is set to DAT, heating, compressors,
and the economizer are controlled to maintain the discharge air
temperature at a desired setpoint. This configuration is typically
used on units equipped with variable air volume supply fans .
When the Control Type is set to (single zone VAV), heating,
compressors and the economizer are controlled to maintain
the discharge air temperature at the desired setpoint while
the variable volume supply fan is modulated to maintain the
temperature of the zone at the desired heating and cooling
setpoints . In heating mode the supply fan capacity is increased
as the zone temperature falls and decreased as the zone
temperature rises .

Heat/Cool Changeover

In general, a unit configured for discharge air temperature
control either operates to deliver the cooling discharge
temperature set point using economizer and/or mechanical
cooling or the heating discharge air temperature set point using
the heating equipment . Cooling and heating never operate
simultaneously. A unit configured for zone (or space comfort)
control either operates to maintain the Occupied or Unoccupied
Cooling Set Point using economizer and/or mechanical cooling
or the Occupied or Unoccupied Heating Set Point using the
heating equipment .
The occupied or unoccupied cooling/occupied or unoccupied
heating setpoints can be set via the keypad/display or based
on a signal from an optional space temperature sensor with set
point adjustment capability. The following sections describe the
unit heat/ cool changeover function .
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