11
RT-PRC016-EN
Selection
Procedure - IP Units
Cooling Capacity
Step 1
Calculate the building’s total and sensible
cooling loads at design conditions. Use
the Trane calculation methods or any
other standard accepted method.
Factors used in unit selection:
A
Total Cooling Load: 59 MBh
B
Sensible Cooling Load: 40 MBh
C
Airflow: 2000 cfm
D
Electrical Characteristics: 380-415/50/3
E
Summer Design Conditions: Entering
Evaporator Coil: 80 DB, 67 WB Outdoor
Ambient: 95
F
External Static Pressure: 0.45 in. wg
Step 2
Table PD-1a shows that a TSC060AD has
a gross cooling capacity of 62.0 MBh and
46.4 MBh sensible capacity at 2000 cfm
and 95 DB outdoor ambient with 80 DB,
67 WB air entering the evaporator.
To Find Capacity at Intermediate
Conditions Not in the Table
When the design conditions are between
two numbers that are in the capacity
table, interpolation is required to
approximate the capacity. Note:
Extrapolation outside of the table
conditions is not recommended.
Step 3
In order to select the correct unit which
meets the building’s requirements, the
fan motor heat must be deducted from
the gross cooling capacity. The amount
of heat that the fan motor generates is
dependent on the effort by the motor -
cfm and static pressure. To determine
the total unit static pressure:
External Static (duct system)
0.45 wg
Standard Filter 1 in.
0.15 wg
from Table PD-21a
Economizer
0.02 wg
(100% Return Air)
from
Table PD-21a
Electric Heater Size 26 MBh
0.07 wg
from Table PD-21a
Total Static Pressure
0.69 wg
Note:
The Evaporator Fan Performance
Table PD-6a has deducted the pressure
drop for a 1 in. filter already in the unit
(see note below Table PD-6a). Therefore,
the actual total static pressure is 0.69 -
0.15 (from Table PD-21a) = 0.50 wg.
With 2000 cfm and 0.50 wg.
Table PD-6a shows .83 bhp for this unit.
Note below the table gives a formula to
calculate Fan Motor Heat,
Fan Motor Heat (MBh) =
2.915 x (Fan BHP) + 0.451
= 2.915 x 0.83 + 0.451 = 2.87 MBh
Now subtract the fan motor heat from
the gross cooling capacity of the unit:
Net Total Cooling Capacity
= 62 MBh - 2.87 = 59.1 MBh.
Net Sensible Cooling Capacity
= 46.4 MBh - 2.87 = 43.5 MBh.
Step 5
If the performance will not meet the
required load of the building’s total or
sensible cooling load, try a selection at
the next higher size unit.
Heating Capacity
Step 1
Calculate the building heating load using
the Trane calculation form or other
standard accepted method.
Step 2
Size the system heating capacity to
match the calculated building heating
load. The following are building heating
requirements:
A
Total heating load of 15 MBH
B
2000 cfm
C
380 volt/3 phase Power Supply
The electric heat accessory capacities are
listed in Table PD-23a. From the table,
the smallest heater will deliver 26 MBh at
380 volts. Referring to Table ED-2, the
electric heater accessory selection is
BAYHTRR412A.
Air Delivery Selection
External static pressure drop through the
air distribution system has been
calculated to be 0.45 inches of water.
From Table PD-21a static pressure drop
through the economizer is 0.02 and the
26 kW heater is 0.07 inches of water (0.45
+ 0.02 + 0.07). Enter Table PD-6a for a
TSC060AD at 2000 cfm and 0.54 static
pressure. The standard motor will give
the desired airflow at a rated bhp of
about 1.01.
Accessory Selection
Select accessories needed to
accommodate the application.
