Trane SS-PRC003-EN manual Selection Procedure, Cooling Capacity, Heating Capacity

Selection Procedure

Cooling Capacity

Step 1 — Calculate the building’s total and sensible cooling loads at design conditions. Use theTrane calculation form or any other standard accepted method.

Step 2 — Size the equipment usingTable PD-1. 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/67WB (27 DB/19WB C)

Outdoor Ambient: 95° F (35° C) c

Total Cooling Load: 75 MBh (22 kW) d

Sensible Cooling Load: 53 MBh (15.5 kW)

e

Airflow: 3000 cfm (5097 m3/h)

External Static Pressure: 0.77 in. (192.5 Pa)

Table PD-1 shows that aTTA075A matched with aTWE075A has a gross cooling capacity of 86.5 MBh (25.3 kW) and 64.4 MBh (18.8 kW) sensible capacity at 95 DB (35° C) ambient and 3000 cfm (5097 m3/h) and 80 DB/67WB (27 DB/19WB) air entering the evaporator.

To find the net cooling capacities, fan motor heat must be subtracted. Determine the total unit static pressure:

	In.	Pa
External Static	0.77	193
Standard Filter	0.10	25
Supplementary
Electric Heat	0.23	57
Total Static Pressure	1.10	275

Note:The Evaporator Fan Performance Table has included the effect of a 1 in. (250 Pa) filter already.Therefore, the actualTotal Static Pressure is 1.10 - 0.10 = 1.00 in. (275 - 25 = 250 Pa).

With 3000 cfm (5097 m3/h) and 1.00 inches (250 Pa), Table PD-29 shows a 1.17 bhp (0.8 kW).

Note:The formula below the table can be used to calculate Fan Motor Heat,

3.5x Bhp = MBh

3.5x 1.17 = 4.10 MBh

(1.375 x (kW) = kW)

(1.375 x 0.8 = 1.1 kW)

NetTotal Cooling Capacity =

86.5MBh – 4.10 = 82.4 MBh

18.8- 1.1 = 17.7 kW

Net Sensible Cooling Capacity =

64.4MBh – 4.10 = 60.3 MBh

25.3- 1.1 = 24.2 kW

Heating Capacity

Step 1 — Calculate the building heating load.

Step 2 — Size the system heating capacity to match the calculated building heating load.The following are building heating requirements:

a

Total Heating Load at 97.0 MBh (28.4 kW) b

3000 cfm (5097 m3/h) c

Electric Supplementary Heaters

Table PD-39, the 34.88 kW heater has a capacity of 119,045 btu. FromTable ED-5, the 34.88 kW indicates the heater model number is BAYHTRL435A.This heater will adequately cover the building’s heating requirement.

Air Delivery Selection

External static pressure drop through the air distribution system has been calculated to be 0.77 inches (192.5 Pa) of water gauge. FromTable PD-38 static pressure drop through the electric heater is 0.23 inches (57.5 Pa) of water (0.77 + 0.23 = 1.00 in.) (192.5 + 57.5 = 250 Pa). EnterTable 39-1 forTWE075AD at 3000 cfm (5097 m3/h) and 1.00 static pressure (250 Pa).The standard motor at 821 rpm will give the desired airflow.

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