41
SECTION 2 – STARTUP AND OPERATION
FORM 145.32-IOM5
ISSUE DATE: 04/08/2019
2
8. Measure the evaporator fan motor's amp draw.
9. Set the room thermostat fan switch to OFF.
10. Turn the unit electrical power OFF.
Operating Instructions
1. Turn the unit's electrical power ON.
2. Set the room thermostat to lower than the room
temperature.
3.
After the built-in time delay (5 minutes), the first
stage compressors energize.
Post Start Checklist
1. Verify the proper system pressures.
2. Measure the temperature drop across the evapora-
tor coil.
MICROPROCESSOR CONTROLLER
Units come with the state of the art Smart Equipment
control (SEC) system. All units are factory commis-
sioned, configured, and run tested. The SEC can be con-
figured to use with a standard thermostat, a zone sensor,
or to communicate with the field controller (FC) bus us-
ing BACnet
®
MS/TP, Modbus
™
or N2 protocols.
Temperature Sensors
Each unit comes with standard supply air temperature
(SAT) and return air temperature (RAT) sensors. The
outside air temperature (OAT) is provided with the
airside economizer option. All sensors are field wired
and installed.
USB Port
The controller comes with a long list of features in-
cluding data logging, current and previous system
faults, and software update capabilities using the on-
board USB port and a common flash drive. Energy use
monitoring capabilities allow custom tailoring. This al-
lows a system to work more efficiently at all times and
occupancy levels. Self-test and startup reports are also
available from the board through the USB port.
LCD Display
The board has an easy to read, built-in LCD display and
easy to use buttons and a navigation joystick. These
features allow the user to quickly navigate the menus
that display the unit status, options, current function,
supply, return and outdoor temperatures, fault codes,
and other information.
Safety Monitoring
The control monitors the following values:
• Outdoor, supply, and return air temperatures
• The high and low pressure switch status on the
independent refrigerant circuits
• The voltage supplied to the unit. If the low voltage
is due to a brown out, or some other electrical is-
sue occurs, the control protects the unit
Low Ambient
With a low ambient damper kit or VFD on the con-
denser installed, an integrated low ambient control
allows units to operate in the cooling mode down to
0.0°F outdoor ambient. Optionally, when the OAT is
low and with the airside economizer option installed,
the control board can be programmed to lock out the
compressors.
Anti-Short Cycle Delay (ASCD) Protection
To assist compressor life, the standard control incor-
porates an ACSD. The compressor reliability is further
ensured by programmable minimum runtimes.
Fan Delays
Fan on and fan off delays are fully programmable. Fur-
thermore, the heating and cooling fan delay times are
independent of one another. All units are programmed
with default values based upon their cooling or heating
capacity configuration.
Nuisance Trip Protection and Three Strikes
To prevent nuisance calls, the control board has three
soft faults before a hard lock out operation. The high/
low-pressure switch, anti-freeze protection, low volt-
age, or heating high limit must trip three times within
two hours before the unit control board locks out the
associated compressor. The LCD screen displays an
alarm message.
Lead-Lag
An integrated lead-lag option is available However,
never enable it on DSH units. This option can be se-
lected on the unit control board. The default factory
setup is always disabled.
Enabling lead-lag function affects logic
of DSH unit and disables unit operation.
