Selection Procedure - Carrier 50TFF007-014 Product Data

Selection procedure (with 50TFF012 example) — SI
I. Determine cooling and heating requirements
at design conditions.
Given:
Required Cooling Capacity (TC) . . . . . . . . . 28 kW
Sensible Heat Capacity (SHC) . . . . . . . . . . 19 kW
Required Heating Capacity . . . . . . . . . . . . 18 kW
Condenser Entering-Air Temp . . . . . . . . . . . 36 C
Evaporator Entering-Air Temp . . . . . . 26.7 C edb,
Evaporator Air Quantity. . . . . . . . . . . . . 1520 L/s
External Static Pressure (ESP). . . . . . . . . . .300 Pa
Electrical Characteristics (V-Ph-Hz) . . . . . 400-3-50
Edb — Entering dry bulb
Ewb — Entering wet bulb
Durablade economizer required.
II. Select unit based
capacity.
Enter the 50TFF012 Cooling Capacities table on
page 18 at condenser entering temperature of
36 C, evaporator-air entering at 1520 L/s, 26.7 C
db and 20 C wb. The 50TFF012 unit will provide
cooling capacity of 30.1 kW and a sensible heat
capacity of 21.2 kW. For evaporator-air tempera-
ture other than 26.7 C edb, calculate sensible heat
capacity correction, as required, using the formula
found in the notes following the Cooling Capacities
table on page 19.
NOTE: Unit ratings are gross capacities and do not
include the effect of evaporator-fan motor (IFM)
heat. To calculate net capacities, see Step V.
III. Select electric heat:
Heating load required is 18 kW.
Enter the Electric Heating Capacities table (page 33)
for the 50TFF012 at 400-3-50. The 19.3 kW
heater at 400 v most closely satisfies the heating
required.
20 C ewb
on required cooling
IV. Determine fan speed and power require-
ments at design conditions.
Before entering the Fan Performance tables, calcu-
late the total static pressure required based on unit
components. From the given and the Pressure Drop
tables (page 33), find:
External static pressure
Economizer
Electric Heat
Total static pressure
Enter the Fan Performance table for the 50TFF012
vertical discharge unit on page 23. Find the fan r/s
and kilowatts at 323 Pa and 1520 L/s. Note that
the fan speed is 14.5 r/s and power required is
1.56 kW (interpolation required). The standard
motor will adequately handle the job requirements.
V. Determine net capacities.
Capacities are gross and do not include the effect of
evaporator-fan motor heat. Use IFM kW from Fan
Performance table on page 23.
Determine net cooling capacity as follows:
Net capacity = gross capacity – IFM kW
= 30.1 kW – 1.56 kW
= 28.5 kW
Net sensible capacity = 21.2 kW – 1.56 kW
Determine net heating capacity as follows:
Net capacity = gross capacity + IFM heat
= 19.3 kW + 1.56 kW
= 24.9 kW
300 Pa
14 Pa
323 Pa
= 19.6 kW
9 Pa
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