Daikin MPS - Field Wiring and Signals

fIeld wIrIng
Below are descriptions of the various options and features
that may require eld wiring to the MicroTech III controller.
Refer to the job plans and specications and the as-built wiring
schematics for information regarding the specic unit.
Field Output Signals
The following outputs may be available for eld connections to
a suitable device.
Remote Alarm Output
The Remote Alarm Output (MCB-DO9) supplies 24 VAC to
terminal 115 on the eld terminal block (TB2) when the output
is on. To use this signal, wire the coil of a eld supplied and
installed 24 VAC pilot relay across terminals 115 and 117 on
TB2. When this output is on, 24 VAC is supplied from the
control transformer through the output relay to energize the
eld relay. Refer to the as-built wiring diagrams.
The digital alarm output indicates the alarm group that contains
the highest priority active alarm. This output (MCB-DO9) is On
when no alarms are active. The options for the action of this
output when an alarm in a group occurs are On, Fast Blink,
Slow Blink, or Off. These can be edited via the Alarm Out
Cong menu in the Extended menus on keypad/display. The
default values for the three groups of alarms are:
Warnings - Off
Problems - Slow Blink
Faults - Fast Blink
A user could eliminate any signal of a particular group of
alarms through this output by selecting On for that alarm group
in the keypad/display.
VAV Box Signal/Fan Operation Signal
The VAV Box Signal/Fan Operation signal affects how Digital
Output #10 operates. The output is either a supply fan
operation indication or a VAV box signal depending on how
this parameter is set. Digital output #10 is wired to a set of
terminals for eld use.
Fan Operation
The Fan Operation Output (MCB-DO10) supplies 24 VAC to
terminal 116 on the eld terminal block (TB2) when the output
is on. To use this signal, wire the coil of a eld supplied and
installed 24 VAC pilot relay across terminals 116 and 117 on
TB2. When this output is on, 24 VAC is supplied from the
control transformer through the output relay to energize the
eld relay. Refer to the as-built wiring diagrams.
The Fan Operation output is on when the unit is not Off and
when both the unit is Off and airow is detected. It is off when
the unit is off and airow is not detected.
VAV Output
In the Heating state, the VAV Output is turned off to indicate
that hot air instead of the normal cool air is being supplied to
the VAV boxes. The VAV boxes are driven to their Heating
Position when hot air is provided based on either the normally
open or normally closed contacts of the VAV output. The VFD
will continue to be controlled to maintain the desired duct static
pressure. This output is also off when the unit is in the Startup
or Recirculation states. If this output is in the Heat (off) position
when the unit enters the Fan Only state or Minimum DAT
Control state, the output remains off for an adjustable Post
Heat Time. When the Unit State is Off, the VAV Box Output
is in the Cool (on) position unless airow is detected. When
airow is detected, it switches to the Heat (off) position.
Cooling Only Units
For cooling only VAV systems, the VAV Box Output can
override zone thermostat control and drive the VAV boxes fully
open to facilitate air circulation during the Recirc operating
state. During this time, the VAV Box Output is in the OFF
(or heat) position (eld-installed pilot relay de-energized).
VAV units have a “post heat” control feature that forces the
VFD speed to a minimum before turning on the VAV Box
Output when the Recirc operating state is complete. Post
heat operation prevents excessive duct static pressure that
could otherwise occur when the zone thermostats regain VAV
box control. The setting of a “post heat” timer determines the
duration of post heat operation. This timer is set to zero at the
factory and must be set to a non-zero value to enable the “post
heat” function.
Units with Modulating Heat
The VAV Box Output should be used to switch the VAV boxes
between heating and cooling control. While the unit is in
Startup, Recirc, or Heating operating state (UnocHtg, MWU, or
Heating), the VAV Box Output is in the OFF (or heat) position
(eld-installed pilot relay de-energized) switching the VAV
boxes into heating operation.
VAV units have a “post heat” control feature that forces the
VFD speed to a minimum before closing the VAV Box Output
when the unit leaves the Recirc or Heating operating state.
“Post heat” operation prevents excessive duct static pressure
that could otherwise occur when the zone thermostats regain
VAV box control. When the unit is not in Startup, Recirc, or
Heating operating state, the VAV Box Output is in the ON (or
cool) position (eld-supplied pilot relay energized) switching the
boxes to cooling control.
IM 919-3 • MICROTECH III CONTROLLER 24 www.DaikinApplied.com
fIeld wIrIng