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CB(X)26UH SERIES
Check−out Procedures
IMPORTANT
During installation, service or maintenance, make sure
that copper tubing does not rub against metal edges or
other copper tubing. Care should also be taken to ensure
that tubing does not become kinked. Use wire ties to se-
cure tubing to prevent movement.
Do not secure electrical wires to tubing that carries hot
refrigerant gas. Heat from the tubing may melt the wiring
insulation causing a short circuit.
NOTE − Refer to outdoor unit installation instructions for
system start−up instructions and refrigerant charging
instructions.
PRE-START-UP CHECKS
S
Is the air handler properly and securely installed?
S
If horizontally configured, is the unit sloped up to 1/4
inch toward drain lines?
S
Will the unit be accessible for servicing?
S
Has an auxiliary pan been provided under the unit with
separate drain for units installed above a finished
ceiling or in any installation where condensate
overflow could cause damage?
S
Have ALL unused drain pan ports been properly
plugged?
S
Has the condensate line been properly sized, run,
trapped, pitched, and tested?
S
Is the duct system correctly sized, run, sealed, and
insulated?
S
Have all cabinet openings and wiring been sealed?
S
Is the indoor coil factory-installed TXV properly sized
for the outdoor unit being used?
S
Have all unused parts and packaging been disposed
of?
S
Is the filter clean, in place, and of adequate size?
S
Is the wiring neat, correct, and in accordance with the
wiring diagram?
S
Is the unit properly grounded and protected (fused)?
S
Is the thermostat correctly wired and in a good
location?
S
Are all access panels in place and secure?
CHECK BLOWER OPERATION
S
Set thermostat to FAN ON.
S
The indoor blower should come on.
CHECK COOLING OPERATION
S
Set thermostat to force a call for cooling
(approximately 5ºF lower than the indoor ambient
temperature).
S
The outdoor unit should come on immediately and the
indoor blower should start between
30 − 60
seconds
later.
S
Check the airflow from a register to confirm that the
system is moving cooled air.
S
Set the thermostat 5ºF higher than the indoor
temperature. The indoor blower and outdoor unit
should cycle off.
CHECK ELECTRIC HEATER (IF USED)
S
Set thermostat to call for auxiliary heat (approximately
5°F above ambient temperature). The indoor blower
and auxiliary heat should come on together. Allow a
minimum of 3 minutes for all sequencers to cycle on.
S
Set the thermostat so that it does not call for heat.
Allow up to 5 minutes for all sequencers to cycle off.
Operation
COOLING (COOLING ONLY OR HEAT PUMP)
When the thermostat calls for cooling, 24 volts is put on the
blower time−delay relay coil. After a delay, the indoor
blower relay energizes. The normally open contacts close,
causing the indoor blower motor to operate. The circuit
between R and Y is completed, closing the circuit to the
contactor in the outdoor unit, starting the compressor and
outdoor fan motor.
On heat pumps, circuit R and O energizes the reversing
valve, switching the valve to the cooling position. (The
reversing valve remains energized as long as the
thermostat selector switch is in the COOL position.)
At the completion of the cooling demand and after the
relay’s time-delay, the compressor and outdoor fan will
cycle off.
HEATING (ELECTRIC HEAT ONLY)
When the thermostat calls for heat, the circuit between R
and W is completed, and the heat sequencer is energized.
A time delay follows before the heating elements and the
indoor blower motor come on. Units with a second heat
sequencer can be connected with the first sequencer to W
on the thermostat subbase, or they may also be connected
to a second stage on the subbase.
HEATING (HEAT PUMP)
When the thermostat calls for heating, 24 volts is put on the
blower time−delay relay coil. After a delay, the normally
open contacts close, causing the indoor blower motor to
operate. The circuit between R and Y is completed, closing
the circuit to the contactor in the outdoor unit, starting the
compressor and outdoor fan motor. Circuit R and G
energizes the blower relay, starting the indoor blower
motor.
If the room temperature should continue to fall, the circuit
between R and W1 is completed by the second-stage heat
room thermostat. Circuit R−W1 energizes a heat
sequencer. The completed circuit will energize
supplemental electric heat (if applicable). Units with a
second heat sequencer can be connected with the first
sequencer to W1 on the thermostat. They may also be
connected to a second heating stage W2 on the thermostat
subbase.
TIME DELAY RELAY
On early production units, the indoor blower relay
energizes after a
30
second delay and it remains
energized for
30
seconds after the call is satisfied.
The indoor blower will remain on for approximately
30 seconds before cycling off.
