10
RT-PRC016-EN
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: 16.7 kW
B
Sensible Cooling Load: 11.7 kW
C
Airflow: 3400 m
3
/h
D
Electrical Characteristics: 380-415/50/3
E
Summer Design Conditions: Entering
Evaporator Coil: 27 DB, 19 WB Outdoor
Ambient: 35
F
External Static Pressure: 110 Pa
Step 2
Table PD-1 shows that a TSC060AD has a
gross cooling capacity of 17.8 kW and
14.4 kW sensible capacity at 3400 m
3
/h
and 35 DB outdoor ambient with 27 DB,
19 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)
110 Pa
Standard Filter 1 in.
37 Pa
from Table PD-21
Economizer
5 Pa
(100% Return Air)
from
Table PD-21
Electric Heater Size 7.5 kW
17 Pa
from Table PD-21
Total Static Pressure
169 Pa
Note:
The Evaporator Fan Performance
Table PD-6 has deducted the pressure
drop for a 25 mm filter already in the
unit (see note below Table PD-6).
Therefore, the actual total static pressure
is 169-17 (from Table PD-21) = 152 Pa.
With 3400 m
3
/h and 152 Pa
Table PD-6 shows .67 kW for this unit.
Note below the table gives a formula to
calculate Fan Motor Heat,
Fan Motor Heat (kw) =
1.144 x (Fan kW) + 0.132
= 1.144 x 0.67 + 0.132 = 0.90 kW
Now subtract the fan motor heat from
the gross cooling capacity of the unit:
Net Total Cooling Capacity
= 17.8 kW - 0.9 = 16.9 kW.
Net Sensible Cooling Capacity
= 14.4 kW - 0.9 = 13.5 kW.
Step 4
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 5 kW
B
2000 cfm
C
380 volt/3 phase Power Supply
The electric heat accessory capacities are
listed in Table PD-23. From the table, the
smallest heater will deliver 7.5 kW at
380 V. Referring to Table ED-2, the
electric heater selection is
BAYHTRR412A.
Air Delivery Selection
External static pressure drop through the
air distribution system has been
calculated to be 110 Pa. From Table PD-
21 static pressure drop through the
economizer is 5 Pa and the 7.5 kW heater
is 17 Pa (110 + 5 + 17). Enter Table PD-6
for a TSC060AD at 3400 m
3
/h and 132 Pa
static pressure. The standard motor will
give the desired airflow at a rated kW of
0.64.
Accessory Selection
Select accessories needed to
accommodate the application.
Selection
Procedure - SI Units
