36
FORM 145.18-IOM1
ISSUE DATE: 8/30/2018
SECTION 2 - OPERATION
• The blower and compressor operation are
smooth with no frost observed in the refrig-
erant circuit.
10. Set the thermostat to maintain the desired space
temperature.
11. Check all water connections for any leaks, includ-
ing condensate drain hose connections.
SYSTEM LOOP TEMPERATURE
Loop temperatures affect unit performance, power
consumption (efficiency), maintenance and reliability,
and noise levels. High EWT in cooling mode above
rated conditions of 86.0°F EWT increases power con-
sumption and compressor noise levels. Sustained op-
eration above 100°F EWT can increase maintenance
costs, and increased compressor noise can affect oc-
cupancy comfort. The unit is designed to operate up to
110.0°F EWT for intermittent periods when high load
conditions elevate system loop temperatures.
It is not recommended to set system loop temperatures
at 110.0°F in case high load conditions cause supply
loop temperatures to exceed 110.0°F EWT. Unit sound
performance can be negatively impacted at high EWT.
During heating season, the maximum operating loop
temperature is 90.0°F EWT. For optimal unit perfor-
mance, it is recommended to maintain system loop
temperatures at or above the rated conditions of 68.0°F
EWT. If system loop temperatures are low and freezing
the coaxial is possible, the system loop must contain a
glycol fluid mixture that is adequate to prevent freez-
ing. The minimum loop temperature with glycol mix-
ture is 20.0°F EWT. Lower loop temperatures result in
lower efficiency and heating capacity.
High system loop temperatures may nega-
tively affect unit performance, efficiency,
maintenance and reliability, and noise
levels.
TABLE 7 -
OPERATING LIMITS
COOLING
HEATING
MINIMUM EWT
30.0°F
20.0°F
MAXIMUM EWT
110.0°F
90.0°F
FAN SPEED ADJUSTMENT
Multi-speed direct drive motors are used in all units as
standard. Permanent split capacitor (PSC) fan motors
have a minimum of three selectable speeds. EC motors
(ECMs) have five speeds, however only two speeds are
recommended and available for selection.
Optional ECMs increase operating efficiency by con-
suming fewer watts than standard PSC motors. Motors
are factory programmed and cannot be re-programmed
in the field. Each motor contains five low voltage speed
taps. Two speed taps are used as standard.
Blower speed taps are factory set for optimum heating
and cooling airflow ranges. See
Table 8 on page 37
for factory blower speed settings and minimum operat-
ing airflow.
Operating the unit below the minimum
airflow may result poor heating/cooling
performance and periodic unit lockout.
A unit mounted two-speed fan switch located on the
electrical box cover allows the fan speed to switch
from LOW and HIGH. This enables the fan speed to
meet site conditions such as increased ductwork static
pressure or the use of higher efficient filters.
Perform a test run on the installed system to ensure op-
eration with sufficient heating and cooling airflow. Ex-
cessive ductwork static pressure results in an improper
volume of airflow. High airflow volumes result in el-
evated noise levels and can affect occupancy comfort.
Lock all electrical power supply switches
in the OFF position before servicing the
unit. Failure to disconnect power supply
may result in electrical shock or even
death.
