Selection Procedure: Ip Units - Trane WSC060-120 User Manual

Cooling Capacity
Step 1
Calculate the building's total and
sensible cooling loads at design
conditions. Use the Trane calculation
form or any other standard accepted
method.
Step 2
Size the equipment using Table PD-1a.
Match the cooling loads at design
conditions.
Example: The following are the building
cooling requirements:
A
Electrical Characteristics: 380–415/50/3
B
Summer Design Conditions:
Entering Evaporator Coil: 80 DB/ 67 WB
Outdoor Ambient: 95
C
Total Cooling Load: 53 MBh
D
Sensible Cooling Load: 33 MBh
E
Airflow: 2,000 cfm
External Static Pressure: .52 in. w.g.
F
Downflow Configuration
PKGP-PRC004-EN
Selection
Procedure - IP Units
Table PD-1a shows that a WSC060AD
has a gross cooling capacity of 59.0 MBh
and 45.7 MBh sensible capacity at 95
degree ambient and 2,000 cfm with 80
DB/67 WB air entering the evaporator.
To find the net cooling capacities, fan
motor heat must be subtracted.
Determine the total unit static pressure:
External Static
Standard Filter 1 in.
Economizer
Supplementary Electric Heat 0.083 in.
Total Static Pressure
Note: The Evaporator Fan Performance
Table PD-9a has deducted the pressure
drop for a 1 in. filter already in the
downflow unit.
Therefore, the actual Total Static
Pressure is 0.933 – 0.15 = 0.78. With
2,000 cfm and 0.78 inches, Table PD-9a
shows 1.00 bhp.
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 1.00 + 0.451 = 3.37 MBh
Net Total Cooling Capacity =
57 – 3.37 = 53.6 MBh
Net Sensible Cooling Capacity =
38 – 3.37 = 34.6 MBh
Heating Capacity
Step 1
Calculate the building heating load using
the Trane calculation form or other
standard accepted method.
Step 2
Size the equipment using Table PD-5a to
match the heating loads at design
0.52 in.
conditions.
0.15 in.
A
0.18 in.
Total Heating Load: 50 MBh
0.933 in.
B
Outdoor Ambient (Winter) 17 DB
C
Indoor Return Temperature: 70 DB
D
Airflow: 2,000 cfm
Use the portion of Table PD-5a for the
WSC060AD to determine capacity at
winter design conditions. The
mechanical heating portion of the heat
pump will provide 29.1 MBh.
Step 3
Because 29.1 MBh is less than the
building's required heating capacity at
winter design conditions, a
supplementary heater must be selected.
50 MBh – 29.1 MBh = 29.9 MBh
From Table PD-9a, at 380 volts, the 38.0
MBh Heater will be adequate to do the
job.
10.9 kW 38.0 MBh
From Table ED-2 select heater
BAYHTRR418A (38.0 MBh at 380 volts).
Air Delivery Selection
External static pressure drop through the
air distribution system has been
calculated to be 0.80 inches of water.
Enter Table PD-9a for a WSC060AD at
2000 cfm and 0.80 static pressure. The
standard motor will give the desired
airflow.
Accessory Selection
Select accessories needed to
accommodate the application.
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