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the present firing rate until the heat cycle ends.
7.
When the demand for first and second stage heat
is satisfied, the gas valve is de-energized and the
field selected indoor blower OFF delay begins. The
combustion air inducer begins a 20 second post-purge
period.
8.
When the combustion air post-purge period is
complete, the inducer is de-energized. The indoor
blower is de-energized at the end of the OFF delay.
Applications Using A Single-Stage Thermostat
C - Heating Sequence -- Control Thermostat Selection
DIP Switch in "Single Stage" Position
1.
On a call for heat, thermostat first stage contacts
close, sending a signal to the integrated control. The
integrated control runs a self-diagnostic program and
checks high temperature limit switches for normally
closed contacts and pressure switches for normally
open contacts. The combustion air inducer is energized
at the ignition speed, which is approximately the same
as the inducer speed at 70 percent firing rate.
2.
Once the control receives a signal that the low fire
pressure switch has closed, the combustion air inducer
begins a 15 second pre-purge at the ignition speed.
3.
After the pre-purge is complete, a 20 second initial
ignitor warm up period begins. The combustion air
inducer continues to operate at the ignition speed.
4.
After the 20 second warm up period has ended, the
gas valve is energized and ignition occurs, which
initiates a 10 second ignition stabilization delay. At
the same time, the control module sends a signal to
begin an indoor blower 30 second ON delay. When
the delay ends, the indoor blower motor is energized
at a speed appropriate for the firing rate. After the 10
second ignition stabilization delay expires, the inducer
speed is adjusted to 35 percent speed. The integrated
control also initiates a second-stage ON delay (factory
set at 7 minutes; adjustable to 12 minutes).
5.
If the heating demand continues beyond the second
stage ON delay, the integrated control energizes the
combustion air inducer at 70 percent speed. The indoor
blower motor is adjusted to a speed that matches the
target rate. A fixed, 10 minute third stage on delay is
initiated.
6.
If the heating demand continues beyond the third stage
ON delay, the integrated control energizes the inducer
at high speed. The indoor blower motor is adjusted to
a speed appropriate for the target rate.
7.
When the thermostat heating demand is satisfied,
the gas valve is de-energized and the combustion
air inducer begins a 20 second post-purge. The field
selected indoor blower OFF delay begins.
8.
When the combustion air post-purge period is
complete, the inducer is de-energized. The indoor
blower is de-energized at the end of the OFF delay.
Page 56 of 74
Service
ELECTRICAL SHOCK, FIRE, OR EXPLOSION
Failure to follow safety warnings exactly could result in
dangerous operation, serious injury, death or property
damage.
Improper servicing could result in dangerous operation,
serious injury, death, or property damage.
Before servicing, disconnect all electrical power to
furnace.
When servicing controls, label all wires prior to
disconnecting. Take care to reconnect wires correctly.
Verify proper operation after servicing.
At the beginning of each heating season, system should
be checked as follows by a qualified service technician:
Blower
Check the blower wheel for debris and clean if necessary.
The blower motors are pre-lubricated for extended bearing
life. No further lubrication is needed.
The blower access panel must be securely in place
when the blower and burners are operating. Gas fumes,
which could contain carbon monoxide, can be drawn
into living space resulting in personal injury or death.
Filters
All filters are installed external to the unit. Filters should
be inspected monthly. Clean or replace the filters when
necessary to ensure proper furnace operation. Table 1 lists
recommended filter sizes.
Exhaust and Air Intake Pipes
Check the exhaust and air intake pipes and all connections
for tightness and to make sure there is no blockage.
NOTE: After any heavy snow, ice or frozen fog event, the
furnace vent pipes may become restricted. Always check
the vent system and remove any snow or ice that may be
obstructing the plastic intake or exhaust pipes.
Electrical
1.
Check all wiring for loose connections.
2.
Check for the correct voltage at the furnace (furnace
operating).
3.
Check amp-draw on the blower motor.
Motor Nameplate_____________ Actual___________
Issue 2346
WARNING
HAZARD
WARNING
508364-01
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