Specifications

IM 1059-1 / Page 33 of 36
Troubleshooting the MicroTech III
Controller
General Use and Information
The Microtech III controller is provided with two drive
terminals, R(24VAC) and C(0 VAC) that can be used by the
end user to drive the thermostat inputs (G, Y1, Y2, W1, and
W2) and control inputs (U, E, and O). Any combination of a
single board drive terminal (R or C) may be used to operate
the MicroTech III controller’s control or thermostat inputs.
However, only one drive terminal (R or C) can be connected
to any individual input terminal or damage may result. Some
control inputs are not accessible to the end user (for example,
HP, LP, SLTS, and COF).
Typically the Microtech III 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 indus-
try standard thermostat. The control outputs of the standard
thermostat are then connected to the Microtech III controller
thermostat inputs and control inputs as needed. Any remain-
ing board input(s) may be operated by additional thermostat
outputs or remote relays (dry contacts only).
All Microtech III 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 the
Microtech III controller inputs. No outside power source may
be used to operate the Microtech III controller inputs.
To avoid electrical shock, personal injury or death, be
sure that field wiring complies with local and national fire,
safety, and electrical codes, and voltage to the system is
within the limits shown in the job-specific drawings and
unit electrical data plate(s).
Power supply to unit must be disconnected when
making
field connections. To avoid electrical shock, per-
sonal injury or death, be sure to rigorously adhere to field
wiring procedures regarding proper lockout and tagout of
components
.
DANGER
Figure 40: MicroTech III Unit Controller LED Status
and Faults Troubleshooting Reference
Flash Yellow LED
Read Outputs
Check Timers
Brownout
High
Pressure
R - W 1
R -Y 1
Flash Green LED
Stop Compressor
No
Yes
No
No
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Low
Pressure
Low Suct
Temp Sensor
Low Suct
Temp
Room Temp
Sensor Failure
Condensate
Overflow
Stop Compressor
Flash Red LED
Stop Compressor
Flash Yellow LED
Flash Green LED
Solid Red LED
Stop Compressor
Heating Mode
Run in Cooling
Mode for 1 Min.
No
Yes
Cooling Mode
Turn on
Yellow LED
Stop Compressor
Reversing
Valve On
Time Delay
Start
Compressor
30 Second
Time Delay
Request for
Water Flow