20
Start-Up Procedure and Checklist
Begin with power turned off at all disconnects.
1. Turn thermostat system switch to “Cool,” and fan switch to
“Auto” and turn temperature setting as high as it will go.
2. Inspect all registers and set them to the normal open
position.
3. Turn on the electrical supply at the disconnect.
4. Turn the fan switch to the “ON” position. The blower should
operate in low speed after a 7 second delay.
5. Turn the fan switch to “Auto” position. The blower should
stop after a 65 second delay.
6. Slowly lower the cooling temperature until first stage COOL
(LOW COOL) starts. The blower, both fans, and first stage
compressor should now be operating. The blower should
be operating in low speed at 1175 motor rpm. Allow the
unit to run 10 minutes, make sure cool air is being supplied
by the unit.
7. Lower the cooling temperature further until second stage
COOL (HIGH COOL) starts. The blower, both fans, and both
compressors should now be operating. The blower should
be operating in high speed at 1775 motor rpm. Allow the
unit to run 10 minutes, make sure cool air is being supplied
by the unit.
8. Turn the temperature setting to the highest position,
stopping the unit. The indoor blower will continue to run
for 65 seconds.
9. Turn the thermostat system switch to “OFF” and disconnect
all power when servicing the unit.
LOW AMBIENT COOLING NOTES:
FOR 15 AND 20 TON MODELS: While in the Cooling Mode, to prevent
frost from forming on the evaporator while the unit is operating in
outdoor temperatures of 65°F or lower, it is recommended that a
low ambient kit is used. This is strongly recommended for 2 Speed
models due to the lower airflow while in the first stage of cooling.
To further protect the compressor from damage during low ambient
conditions, a Freezestat Kit (FSK01) can be added that turns the
compressor off when the evaporator temperature drops too low.
FOR 25 TON MODELS: The 25 ton units are equipped with a control
that shuts off one condenser fan when the outdoor temperature
is 44° F or below. This is to assist low ambient cooling down to
24°. An optional Low Ambient kit, LAKT05, is required below 24°
which will enable reliable cooling to occur to a minimum ambient
temperature of zero °F.
HIGH VOLTAGE!
D
ISCONNECT
ALL
POWER
BEFORE
SERVICING
OR
INSTALLING
THIS
UNIT
. M
ULTIPLE
POWER
SOURCES
MAY
BE
PRESENT
. F
AILURE
TO
DO
SO
MAY
CAUSE
PROPERTY
DAMAGE
,
PERSONAL
INJURY
OR
DEATH
.
WARNING
NORMAL SEQUENCE OF OPERATION - COOLING
Refrigeration Sequence Check
With the disconnect switch open, remove the field connected ther-
mostat wire from terminal R on TB1 terminal block. Place a jumper
across terminals R and G, and across R and Y on TB1 terminal block.
Close the disconnect switch. The following operational sequence
should be observed.
1. Current through primary winding of transformer TRANS1
energizes the 24-volt control circuit.
2. To simulate a mechanical call for cooling from the wall
thermostat, place a jumper across terminals R and Y1 of
terminal block TB1.
3.
UNIT WITH ECONOMIZER OPTION:
The compressor circuit
is interlocked through terminals 3 and 4 of the economizer
module. If the outdoor air enthalpy (temperature and
humidity) is not suitable for cooling, the economizer
terminals will be closed permitting compressor to be
energized.
4. The belt drive blower contactor closes its contacts L1, L2
and L3 to T1, T2 and T3 to provide power to the supply fan
motor.
5. Check supply fan rotation. If the supply fan is rotating in
the wrong direction, disconnect and lock off Single Point
Power Block. Do not attempt to change load side wiring.
Internal wiring is set at the factory to assure that the supply
fan and compressors all rotate in the proper direction.
Verification of correct supply fan rotation at initial startup
will also indicate correct compressor rotation. Reconnect
power and check for proper operation.
6. Compressor contactor closes its contacts L1, L2 and L3 to
T1, T2 and T3 to provide power to the compressor motor
COMP 1; COMP 2, if conditions are correct. In addition,
contactor C1 closes its contact L3 to T3 , energizing the
condenser fan motor.
7. Check that each compressor is operating correctly. The
scroll compressors in these units MUST operate in the
proper rotation. To ensure the compressors are operating in
the correct direction, check the compressor discharge line
pressure or temperature after each compressor is started.
The discharge pressure and discharge line temperature
should increase. If this does not occur and the compressor
is producing an exceptional amount of noise, perform the
following checks.
• Ensure all compressors and the supply fan motor are
operating in the proper direction. If a single motor
is operating backwards, check the power wiring for
that motor and correct any leads that have been
interchanged at the contactor or at the motor.
• If all of the motors are operating backward, disconnect
the unit power supply and lock it in the “OFF” position.
Switch two leads of the power supply at the unit Single
Point Power Block. Reconnect power and check for
compressor and supply fan motor operation.
