| Application and Design Information (cont.)
| Typical Piping Arrangement for Direct
Return System |
 |
Unit Operating Limits
Airflow
The minimum recommended airflow for proper system staging and temperature
control is 35% of nominal airflow. However, airflows
below this point can be utilized. Use appropriate minimum settings on the VAV boxes to ensure that the
self-contained unit is not operating in a surge condition. Continuous operation
in a surge condition can cause a fan failure. Check
with your local office for confirmation of acceptability of low airflow operating conditions.
Fixed pitch sheaves are used on the Trane unit. Air balancing adjustments are accomplished by obtaining alternate fixed
pitch sheaves available from the factory.
Waterflow
Use 3 gpm/ton for maximum unit capacity and efficiency. However, 2.5 or 2
gpm/ton may yield significant pumping energy and piping
cost reductions. These reduced water flows may have only a 1-2% impact on
the self-contained unit capacity and efficiency.
Specific waterflow limits are included in the data
tables in this catalog.
Sensors — Location And Wiring Requirements Static Pressure Sensor
Locate the static pressure sensor about two-thirds to three-fourths of the way
down the longest duct run. Stay approximately 10 duct
diameters downstream and 2 duct diameters upstream of any major interferences,
turns or changes in duct diameter.
Pneumatic tubing lengths between the sensor and regulator should not exceed 250
feet for 1/4-inch OD or 500 feet for 3/8-inch OD
tubing.
Choose a static pressure set point at the lowest level that meets customer/code
requirements for air quantity and air quality. A lower
static pressure setpoint reduces fan energy requirements and improves acoustic performance.
Wiring Requirements For Self-Contained Optional Sensors
Wiring requirements for the zone temperature remote reset,
supply air reset, and morning warmup optional sensors are all NEMA CLASS Il. This is economical low voltage (30 volts maximum) wiring. |
