Selection Procedure - Carrier 50TFF007-014 Product Data

Selection procedure (with 50TFF012 example) —
English
I. Determine cooling and heating requirements
at design conditions.
Given:
Required Cooling Capacity (TC) . . . . 96,000 Btuh
Sensible Heat Capacity (SHC) . . . . . .70,000 Btuh
Required Heating Capacity . . . . . . . 62,000 Btuh
Condenser Entering-Air Temp . . . . . . . . . . . 95 F
Evaporator Entering-Air Temp . . . . . . . . 80 F edb,
Evaporator Air Quantity. . . . . . . . . . . . . 3200 cfm
External Static Pressure (ESP). . . . . . . .1.10 in. wg
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 21 condenser entering temperature of 95 F,
evaporator-air entering at 3200 cfm, 80 F db and
67 F wb. The 50TFF012 unit will provide cooling
capacity of 102,500 Btuh and a sensible heat
capacity of 76,000 Btuh. For evaporator-air tem-
perature other than 80 F edb, calculate sensible
heat capacity correction, as required, using the for-
mula found in the notes following the Cooling
Capacities table on page 21.
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 62,000 Btuh.
62,000 Btuh
3413 Btuh/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.
19.3 x 3413 = 65,871 Btuh gross capacity
14
67 F ewb
on required
= 18.2 kW of heat required
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 27. Find the fan rpm
and watts at 1.20 in. wg and 3200 cfm. Note that
the fan speed is 844 rpm and power required is
1430 watts. The standard motor will adequately
cooling handle the job requirements.
V. Determine net capacities.
Capacities are gross and do not include the effect of
evaporator-fan motor heat. Use IFM Watts from Fan
Performance table on page 27.
Determine net cooling capacity as follows:
Net capacity = gross capacity – IFM Watts
= 102,500 Btuh – 1430 Watts x 3.413
= 102,500 Btuh – 4881 Btuh
= 97,619 Btuh
Net sensible capacity = 76,000 Btuh – 4881 Btuh
Determine net heating capacity as follows:
Net Capacity= gross capacity + IFM heat
= 71,119 Btuh
= 65,871 + 4881
= 70,752 Btuh
1.10 in. wg
0.04 in. wg
0.06 in. wg
1.20 in. wg
Btuh
Watts