17
I. Determine cooling and heating load
requirements.
Given:
Total Cooling Load (TC) . . . . . . . . .112,000 Btuh
Sensible Heat Capacity (SHC) . . . . . .86,000 Btuh
Temperature Air Entering
Outdoor Unit (Edb) . . . . . . . . . . . . . . . . . . . .95 F
Temperature Air-Entering Indoor
Unit . . . . . . . . . . . . . . . . . . 80 F edb/67 F ewb
Indoor-Air Quantity . . . . . . . . . . . . . . . 4,000 cfm
External Static Pressure . . . . . . . . . . . .0.80 in. wg
Heating Load at Winter Design . . . .120,000 Btuh
Temperature Air Entering Indoor Unit,
Heating. . . . . . . . . . . . . . . . . . . . . . . . . . .70 F
Winter Design, Outdoor. . . . . . . . . . . . . . . . . 0° F
Power Supply (V-Ph-Hz) . . . . . . . . . . . . 230-3-60
II. Select system that satisfies load
requirements.
Select heat pump systems to satisfy cooling design
load requirements. Enter the Combination Ratings,
Gross Capacities — Cooling tables, page 19. At
outdoor unit air entering temperature of 95 F,
indoor unit air entering at 4,000 cfm, and 80 edb/
67 ewb, find that a 38AQS012 outdoor unit
matched with a 40RMQ012 indoor unit delivers a
TC of 113,000 Btuh and SHC of 87,000 Btuh at
design conditions. These values satisfy the cooling
requirements of the examples shown.
III. Determine the heating capacity of selected
system.
Enter the Combination Ratings Net Capacities —
Heating tables on page 20 for units 38AQS012 and
40RMQ012. Under the 0° F column, read down to
the 70 F indoor-air section at 4,000 cfm and find an
integrated heating capacity of 43,400 Btuh. The
heating requirement is 120,000 Btuh, and the unit
capacity is 43,400; therefore, 76,600 Btuh of sup-
plemental electric heat is needed.
Select an electric heater that satisfies the voltage
designation and the supplemental heat requirement.
Refer to the Electric Heater Data — Indoor Units
table, page 26. The supplemental heating load
required is 76,600 Btuh.
To convert Btuh to kW:
= 22.4 kW of supplemental heat required.
For the 40RMQ012, the heater part no.
CAELHEAT010A00 is rated 25 kW at 240 volts.
To calculate kW at 230 volt, use the voltage multi-
plier found on page 27.
25 kW x 0.918 (230 volt multiplier) = 22.95 kW at
230 volts.
25 kW x 0.918 x 3413 Btuh/kW = 78,238 Btuh at
230 volts.
The output of the CAELHEAT010A00 heater de-
rated for 230 volt is 78,238 Btuh which satisfies the
supplemental heat requirement for this example.
IV. Determine fan rpm and bhp (brake
horsepower).
At the Indoor Unit Fan Performance Data table,
page 21, enter the 40RMQ012 section at
4,000 cfm and move to External Static Pressure
(ESP) 0.80 column. Note that the conditions require
879 rpm and 1.69 bhp.
V. Determine motor and drive.
For the 40RMQ012 unit, find the type of drive that
satisfies the 879 rpm requirement in the Drive Data
tables on page 36. The Medium-Static Drive table
shows an rpm range of 733 to 949 which satisfies
this rpm requirement for the example described.
Next, enter the Fan Motor Data tables on page 35,
and find that a 208/230-3-60 standard motor has a
motor hp of 2.4 which satisfies the bhp requirement
for the example described. Select the standard
motor and medium-static drive (option code HC
or FD).
76,000 Btuh
3413 Btuh/kW
Selection procedure (with example)