Rheem RKNL-B073CL15E, Manual, Page: 10 / 80

Air
Selection Procedure
RKNL-B Series
10
To select an RKNL-B Cooling and Heating unit to meet a job
requirement, follow this procedure, with example, using data
supplied in this specification sheet.
1. DETERMINE COOLING AND HEATING REQUIREMENTS
AND SPECIFIC OPERATING CONDITIONS FROM PLANS
AND SPECS.
Example:
Voltage — 208/230V — 3 Phase — 60 Hz
Total Cooling Capacity — 106,000 BTUH [31.0 kW]
Sensible Cooling Capacity — 0 82,000 BTUH [24.0 kW]
Heating Capacity — 150,000 BTUH [43.9 kW]
*Condenser Entering Air — 95°F [35.0 °C] DB
*Evaporator Mixed Air Entering — 65°F [18.3 °C] WB
78°F [25.6 °C] DB
*Indoor Air Flow (vertical) — 3600 CFM [1699 L/s]
*External Static Pressure — 0.40 in. WG [.10 kPa]
2. SELECT UNIT TO MEET COOLING REQUIREMENTS.
Since total cooling is within the range of a nominal 10 ton
[35.1 kW] unit, enter cooling performance table at 95°F
[35.0 °C] DB condenser inlet air. Interpolate between 63°F
[17.2 °C] WB and 67°F [19.4 °C] WB to determine total and
sensi ble capacity and power input for 65°F [18.3 °C] WB
evaporator inlet air at 3750 CFM [1770 L/s] indoor air flow
(table basis):
Total Cooling Capacity = 118,900 BTUH [34.82 kW]
Sensible Cooling Capacity = 99,950 BTUH [29.27 kW]
Power Input (Compressor and Cond. Fans) = 8,950 watts
Use formula in note to determine sensible capacity at 78°F
[25.6 °C] DB evaporator entering air:
99,950 + (1.10 x 3,600 x (1 - 0.03) x (78 - 80))
Sensible Cooling Capacity = 92,268 BTUH [27.02 kW]
3. CORRECT CAPACITIES OF STEP 2 FOR
ACTUAL AIR FLOW.
Select factors from airflow correction table at 3600 CFM
[1699 L/s] and apply to data obtained in step 2 to obtain
gross capacity:
Total Capacity = 118,900 x 0.98 = 116,522 BTUH [34.12 kW]
Sensible Capacity = 92,268 x 0.95 = 87,655 BTUH [25.67 kW]
Power Input = 8,950 x 0.99 = 8,861 Watts
These are Gross Capacities, not corrected for blower motor
heat or power.
4. DETERMINE BLOWER SPEED AND WATTS TO MEET
SYSTEM DESIGN.
Enter Indoor Blower performance table at 3600 CFM [1699
L/s]. Total ESP (external static pressure) per the spec of 0.40 in.
WG [.10 kPa] includes the system duct and grilles. Add from
the table ‘Component Air Resistance’, 0.076 in. WG [.02 kPa]
for wet coil, 0 in. WG [.00 kPa] for downflow air flow, for a
total selection static pressure of 0.476 (0.5) in. WG [.12 kPa],
and determine:
RPM = 769
WATTS = 1,576
DRIVE = L (standard 2 H.P. motor)
5. CALCULATE INDOOR BLOWER BTUH HEAT EFFECT
FROM MOTOR WATTS, STEP 4.
1,576 x 3.412 = 5,377 BTUH [1.57 kW]
6. CALCULATE NET COOLING CAPACITIES, EQUAL TO
GROSS CAPACITY, STEP 3, MINUS INDOOR BLOWER
MOTOR HEAT.
Net Total Capacity = 116,522-5,377 =
111,145 BTUH [32.54 kW]
Net Sensible Capacity = 87,655 - 5,377 =
82,278 BTUH [24.09 kW]
7. CALCULATE UNIT INPUT AND JOB EER.
Total Power Input = 8,861 (step 3) + 1,576
(step 4) = 10,437 Watts
EER =
Net Total BTUH [kW] (step 6)
=
111,145
= 10.65
Power Input, Watts (above) 10,437
8. SELECT UNIT HEATING CAPACITY.
From Physical Data Table read that gas heating output (input
rating x efficiency) is:
Heating Capacity = 182,250 BTUH [53.4 kW]
9. CHOOSE MODEL RKNL-B120CL22E
*NOTE: These operating conditions are typical of a commercial
application in a 95°F/79°F [35°C/26°C] design area with
indoor design of 76°F [24°C] DB and 50% RH and 10%
ventilation air, with the unit roof mounted and centered on
the zone it conditions by ducts.
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