Trane RT-DS-10 - Manual (Page 16)

16
Selection
Procedure
1
Winter outdoor design conditions –
0°F (17.7°C).
2
Total return air temperature – 72°F
(22.2°C).
3
Winter outside air minimum ventilation
load and cfm – 1,000 cfm and
87.2 MBh.
4
Peak heating load 150 MBh.
Utilizing unit selection in the cooling
capacity procedure.
Mixed air temperature = RADB +
% O.A. (OADB - RADB) = 72
+ (0.10) (0-72) = 64.8°F.
Supply air fan motor heat temperature
rise = 20,600 Btu ÷ (1.085 x 10,000) cfm
= 1.38°F.
Mixed air temperature entering heat
module = 64.8 + 1.58 = 65.38°F.
Total winter heating load = peak
heating + ventilation load - total fan
motor heat = 150 + 87.2 - 15 =
222.2 MBh.
Electric Heating System
Unit operating on 415 power supply.
From Table 23-1, kW may be selected
for TC*305 unit to satisfy the winter
heating load. The 67 kW module will do
the job.
Table 23-1 also shows an air
temperature rise of 21.2°F for 10,000
cfm through the 90 kW heat module.
Unit supply temperature at design
heating conditions = mixed air
temperature + air temperature rise =
65.38 + 21.2 = 86.58°F.
Natural Gas Heating System
Assume natural gas supply – 1000
Btu/ft 3 . From Table 23-4, select the low
heat module (243 MBh output) to
satisfy 222 at unit cfm.
Table 23-4 also shows air temperature
rise of 37.3°F for 10,000 cfm through
heating module.
Unit supply temperature design
heating conditions = mixed air
temperature + air temperature rise =
65.38 + 33.5 = 98.89°F.
Air Delivery Procedure
Supply air fan bhp and rpm selection.
Unit supply air fan performance shown
in Table 23-1 includes pressure drops
for dampers and casing losses. Static
pressure drops of accessory
components such as heating systems,
and filters if used, must be added to
external unit static pressure for total
static pressure determination.
The supply air fan motor selected in the
previous cooling capacity
determination example was 5.35 bhp
with 656 rpm. Thus, the supply fan
motor selected is .5 hp.
Chart 16-1 – Fan Motor Heat
To select the drive, enter Table 29-1 for
a 305 unit. Select the appropriate drive
for the applicable rpm range. Drive
selection letter E with a range of 625
rpm, is required for 616 rpm. Where
altitude is significantly above sea level,
use Table 17-2 and 17-3, and Figure
17-1 for applicable correction factors.
Unit Electrical Requirements
Selection procedures for electrical
requirements for wire sizing amps,
maximum fuse sizing and dual element
fuses are given in the electrical service
selection of this catalog.
Unit Designation
After determining specific unit
characteristics utilizing the selection
procedure and additional job
information, the complete unit model
number can be developed. Use the
model number nomenclature on
page 9.