Bryant LEGACY 569J - Manual (Page 13)

13
SELECTION PROCEDURE
Combination ratings for 569J units matched with 524J
Series air handlers are in this book. If unit is used with an
air handler, use the Bryant Electronic Catalog AHU
(Air-Handling Unit) selection program to obtain combined
ratings.
I. Determine cooling load, evaporator-air
temperature, and quantity.
Given:
Total Cooling Capacity
Required (TC) 121,000 Btuh . . . . . . . . . . . . . . . . . . .
Sensible Heat Capacity
Required (SHC) 95,000 Btuh . . . . . . . . . . . . . . . . . . .
Compressor Type Scroll . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature Air Entering
Condenser (Edb) 95_F . . . . . . . . . . . . . . . . . . . . . . . . .
Temperature Air Entering
Evaporator (db/wb) 80_F db, 67_F wb . . . . . . . . . . . .
Evaporator Air Quantity 4,000 cfm . . . . . . . . . . . . . . . . .
External Static Pressure 0.4 in. wg . . . . . . . . . . . . . . . . .
Length of Interconnecting
Refrigerant Piping 25 ft (Linear) . . . . . . . . . . . . . . . . .
Power Supply (V-Ph-Hz) 208/230-3-60 . . . . . . . . . . . . .
II. Select condensing unit air-handler combination.
For this example, select a 569J*12 matched with a
524J12 coil. This 569J*12/524J12 condensing unit
air-handler combination provides 122,000 Btuh of
total cooling capacity and 97,200 Btuh of sensible
capacity at the given conditions. If other
temperatures or airflow values are required,
interpolate the values from the combination ratings.
III. Determine sizes of liquid and suction lines.
Enter Refrigerant Piping Sizes table. The sizes
shown are based on an equivalent length of pipe.
This equivalent length is equal to the linear length
of pipe indicated at the top of each sizing column,
plus a 50% allowance for fitting losses. (For a more
accurate determination of actual equivalent length
in place of using the estimated 50% value, refer to
Bryant System Design Manual.) For this example,
note in the linear length column that the proper pipe
size is 1 /
2
in. for the liquid line and 1 3 /
8
in. for the
suction line.
For extended line lengths over 100 feet, contact
your Bryant representative or application engineer.
IV. Determine fan rpm and bhp (brake horsepower).
Refer to the 524J Air Handler Catalog -- Fan
Performance table. Enter the Air Handler Fan
Performance table at 524J12 at 4000 cfm and move
to the External Static Pressure (ESP) column. Note
that the conditions require 803 rpm at 1.77 bhp.
V. Determine motor and drive.
Enter the Fan Motor Data tables and find the
standard motor for 524J*12 unit rated at 2.4 Hp.
Since the bhp required is 1.77, a standard motor
satisfies the requirement and should be used.
Next, find the type of drive that satisfies the 803
rpm requirement in the Drive Data tables. For the
524J*12 unit, the Standard Drive table shows an
rpm range of 666-863. Since the rpm required is
803, the standard drive satisfies the requirement and
should be used.
CONTROLS
Operating sequences
569J*07--25
At start-up, the thermostat calls for cooling. With all
safety devices satisfied, the compressor contactor and fan
contactor energize, causing the compressor and
outdoor-fan motor to operate. Thermostat contacts
energize, allowing the field-supplied and field-installed
indoor-fan contactor to function. A field-supplied and
field-installed liquid line valve also opens, allowing the
system to function in Cooling mode. As cooling demand
is satisfied, the thermostat contacts break, de--energizing
the contactor and causing the system to shut off. The
liquid line solenoid valve closes, minimizing the potential
for refrigerant migration. The compressor does not restart
until the thermostat again calls for cooling. The system is
protected with a safety circuit so that the system will not
start if a fault exists (i.e., high or low pressure fault). To
reset the safety circuit, set the thermostat to eliminate the
cooling demand, then return it to the original setpoint.
This should be done only once, and if the system shuts
down due to the same fault, determine the problem before
attempting to restart the system.
569J