Fault Conditions; Operating Sequence; Heating Cycle; Cooling Cycle - Oxbox J951X U Series Installation Instructions Manual

Fault Conditions

There is a green and a red LED (labeled "Status") on the
motor control board to provide system faults as described
below. Refer to
Table 14 (page 40)
control board fault conditions.

OPERATING SEQUENCE

The operating sequences for the heating, cooling, and fan
modes are described below. Refer to the field and furnace
wiring diagrams:
Figure 25 (page 24)
Figure 31 (page 30) and Figure 32 (page 31)

Heating Cycle

1. The thermostat calls for heat by energizing the W terminal
with 24VAC.
2. The control verifies the pressure switch is open.
3. If the pressure switch is open, the control energizes the
inducer and waits for the pressure switch to close. The
pressure switch must close within 10 seconds.
4. The control runs the inducer for a 30 second pre-purge.
5. The control energizes the Hot Surface Igniter (HSI) output
for the appropriate warm-up time limit.
6. The control energizes the main gas valve for 3 seconds.
7. If the flame proved and ignites the gas, the control de-
energizes the HSI. The gas valve and inducer remains
energized. The control goes to blower on delay.
8. If flame is present, the control energizes the blower on
the selected HEAT speed 30 seconds after the gas valve
opened. The gas valve and inducer remain energized.
9. When the thermostat demand for heat is satisfied, the
control de-energizes the gas valve. The Inducer output
remains on for a 30 second post-purge period.
10. Blower off timing begins when the thermostat is satisfied.
The control will operate at the selected HEAT speed of 60,
90, 120, or 180 seconds. If the blower off delay jumper is
not present, the fan should still operate for 120 seconds
at the selected HEAT speed. The Indoor blower motor
is de-energized after a blower off delay as selected by
the movable jumper.

Cooling Cycle

1. The thermostat calls for cooling by energizing the Y terminal
with 24VAC.
2. The control energizes the blower in cooling speed and
sends 24VAC to the contactor in the condensing unit
3. When the thermostat removes the call for cooling, the
contactor in the outdoor condensing unit is de-energized
and the control continues to run the fan for a period of 60
seconds.

Fan Mode

• When the thermostat energizes the G terminal for
continuous fan (without calling for heat or cooling), the
indoor fan is energized on the selected FAN speed. See
for fan speed settings.
Figure 26 (page 24)
• If a call for cooling occurs during continuous fan, the
blower will switch over to the selected COOL speed.
• If the W terminal receives a call for heat during continuous
fan, the blower will de energize.
• A call for fan is ignored while in lockout.
to determine motor
Failure to follow safety warnings exactly could
result in serious injury, death or property
damage.
, ,
Figure 26 (page 24)
.
Improper servicing could result in dangerous
operation, serious injury, death or property
damage.
• Before servicing, disconnect all electrical
• When servicing controls, label all wires prior
• Verify proper operation after servicing.
• Proper maintenance is most important to achieve the best
• These maintenance instructions are primarily intended
• Always reinstall the doors on the furnace after servicing.
• Verify the thermostat is properly installed and will not be
• To achieve the best performance and minimize equipment
Air Filter(s) - Air filter(s) are not supplied with the furnace as
shipped from the factory. The installer must provide a high
velocity filter that is appropriately sized to the return air duct
opening or external filter rack.
Never operate the furnace without a filter in place.
Dust and lint can build up on internal components,
resulting in loss of efficiency, equipment damage,
and possible fire.
It is recommended that filter(s) be 1" or 2" thick and be
cleaned or replaced monthly.
Filters designed to remove smaller particles such as pollen,
may require additional maintenance. Filters for side return
and bottom return applications are available from most local
distributors.
Blower Compartment - Dirt and lint can create excessive
loads on the motor resulting in higher than normal operating
temperatures and shortened service life. It is recommended
that the blower compartment be cleaned of dirt or lint that
may have accumulated in the compartment or on the blower
and motor as part of the annual inspection.

MAINTENANCE

WARNING:
ELECTRICAL SHOCK, FIRE OR
EXPLOSION HAZARD
power to furnace.
to disconnecting. Reconnect wires correctly.
performance from a furnace. Follow these instructions for
years of safe, trouble free operation.
to assist qualified technicians experienced in the proper
maintenance and operation of this appliance.
Do not operate the furnace without all doors and
covers in place.
affected by drafts or heat from lamps or other appliances.
failure it is recommended that a yearly maintenance
checkup be performed. At a minimum, this check should
include the following items:
WARNING:
27