OM 931-6 • MicroTech III Unit Controller for WSHP
7
www.DaikinApplied.com
General Use and Information
The MicroTech III unit controller is provided with two
drive terminals, R (24VAC), and C (0VAC) that can be
used to drive the thermostat inputs (G, Y1, Y2, W1, and
W2) and control inputs (U, E and O). Any combination of
or single board drive terminal (R, or C) may be used to
operate the MicroTech III’s unit controller or thermostat
inputs. Some of the control inputs are used within the
Water Source Heat Pump and not accessible to the end
user without a field service tool (laptop with appropriate
software).
Typically the MicroTech III unit controller's R (24VAC)
terminal is used to drive the board’s thermostat inputs
and control inputs by connecting it to the R terminal of
an industry standard thermostat. The control outputs
of the standard thermostat are then connected to the
MicroTech III unit controller's thermostat inputs and
control inputs as needed. Any remaining board input(s)
may be operated by additional thermostat outputs or
remote relays (dry contacts only).
All MicroTech III unit controller inputs must be operated
by dry contacts powered by the control board’s power
terminals. No solid state devices (Triacs) may be used
to operate MicroTech III unit controller inputs. No outside
power sources may be used to operate MicroTech III.
All units must be properly grounded per local code
requirements. See the Installation and Maintenance
bulletin specific to your Water Source Heat Pump.
Occupied Operation
Board LED Status – Occupied
Yellow
Green
Red
Off
On
Off
The board will be in occupied mode if the unoccupied
terminal (U) is open.
Thermostat Inputs (G, Y1, Y2, W1
and W2)
Thermostat inputs used during occupied operation are
G, Y1, and W1, which when energized will activate the
Fan Only, Cooling Mode, and Heating Mode respectively.
Input W2 and Y2 work the same as W1 and Y1
respectively for single circuit units in occupied mode. For
information on W2 and Y2 for dual circuit units, refer to
"Dual Circuit Units" on page
17
.
The MicroTech III unit controller is configured so that
when either the Y1 or W1 input is energized the unit fan
is also activated with Cooling or Heating Modes. In other
words, energizing Y1 and G together will have the same
effect as energizing just Y1. The W1 input has priority
over the Y1 input. In situations when both inputs W1 and
Y1 become energized (unlikely) in any order the unit will
go into the Heating Mode as described below:
1 .
If the unit is in Cooling Mode, Y1 is energized. If
W1 becomes energized and remains energized, the
following will occur:
• The compressor de-energizes.
• The compressor restarts at 360 seconds
(compressor minimum off timer).
• The reversing valve output energizes within 5
seconds of the compressor being energized
(Heating Mode position).
2 .
If the unit is in Cooling Mode, Y1 is energized. If
W1 becomes energized momentarily, the controller
de-energizes the compressor for 360 seconds
(compressor minimum off timer) and then returns to
the cooling mode.
3 .
However, if the unit is in Heating Mode, W1 is
energized. If Y1 becomes energized the unit
remains in Heating Mode.
4 .
Y2 is the second stage cooling, and applies to dual
compressor units.
Control Inputs (HP, LP, SLTS, COF,
U, E, O)
The control inputs are High Pressure (HP), Low
Pressure (LP), Suction Line Temperature Sensor (SLTS),
Condensate Overflow (COF), Unoccupied (U), and
Remote Shutdown (E). The control inputs are in normal
states during occupied mode. The state of each control
in occupied mode during normal operation is as follows:
•
High / Low Pressure (HP, LP): energizes, switch is
closed (no fault).
• Suction Line Temperature Sensor (SLTS):
temperature sensor on the suction line which
provides low temperature protection.
• Condensate Overflow(COF):sensing no condensate
water in the condensate drain pan (no fault).
•
Unoccupied (U): open (no signal).
• Remote Shutdown (E): open (no signal).
• Tenant Override (O): has no effect in occupied mode.
M
ICro
t
eCh
III u
nIt
C
ontroller
