Sequence Of Operations - Lennox CBX25UH­018 Installation And Service Procedure

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Are all access panels in place and secure?
CHECK BLOWER OPERATION
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Set thermostat to FAN ON.
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The indoor blower should come on.
CHECK COOLING OPERATION
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Set thermostat to force a call for cooling (approximately
5ºF lower than the indoor ambient temperature).
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The outdoor and indoor units should come on
immediately.
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Check the airflow from a register to confirm that the
system is moving cooled air.
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Set the thermostat 5ºF higher than the indoor
temperature. The indoor blower and outdoor unit
should cycle off. Air handler should cycle off 45
seconds after the outdoor unit shuts off.
CHECK ELECTRIC HEATER (IF USED)
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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.
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Set the thermostat so that it does not call for heat. Allow
up to 5 minutes for all sequencers to cycle off.
Sequence of Operation
COOLING (COOLING ONLY OR HEAT PUMP)
When the thermostat calls for cooling, 24 volts is put on the
blower time-delay relay coil and then 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 the indoor blower
and outdoor unit should cycle off. Air handler should cycle
off 45 seconds after the outdoor unit shuts 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. Then 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.
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
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.
EMERGENCY HEAT (HEATING HEAT PUMP)
If the selector switch on the thermostat is set to the
emergency heat position, the heat pump will be locked out
of the heating circuit, and all heating will be electric heat (if
applicable). A jumper should be placed between W2 and E
on the thermostat subbase so that the electric heat control
will transfer to the first‐stage heat on the thermostat. This
will allow the indoor blower to cycle on and off with the
electric heat when the fan switch is in the AUTO position.
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circuit will energize