W415-0919 / D / 03.27.13
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4.7
SEQUENCE OF OPERATION - ECM 2.3 AND X-13
1.
Room temperature drops causing the room thermostat call for
fi rst stage heat by connecting “W1” to “R”.
The control verifi es
the limit switch is closed and both the low and high pressure
switches are open. The control energizes the exhauster motor
on high speed and waits for the low pressure switch to close.
The exhauster remains on high speed and begins a 15 second
pre-purge period. The high pressure switch is ignored. If the low pressure switch does not close within 60
seconds, the control will fl
ash “2” on the Status LED, and de-energize the exhauster for 60 minutes.
2.
When the 15 second pre-purge time has elapsed, the control energizes the Hot Surface Igniter (HSI)
output for a 5 second warm-up period (10 seconds on retries). The control energizes the low main gas
valve. 4 seconds after the gas is energized, the control de-energized the HSI output and leaves the gas
energized another 1 second for fl
ame proving. If fl
ame is present at the end of the trial for ignition time,
the control leaves the gas valve energized, inducer on high speed, and begins heat blower on delay.
The
control always ignites on high inducer/low gas and ignores second stage call for heat until low heat is
established for 15 seconds.
3.
Blower on delay time begins when the gas valve is energized. The control provides the ECM (Electronically
Commutated Motor) low heat speed signal when fl
ame is proven, and starts a 30 second soft start (slowly
ramp up) blower delay before full capacity blower level.
4.
When there is a demand for 2
nd
stage heat from Thermostat W2 or automatic staging , the control changes
the inducer from low to high speed. When high pressure switch closes, the control changes indoor blower
speed from Low heat to High heat and energizes high gas output. If the High pressure switch is open the
Green LED will fl
ash. If the High pressure switch is closed the Green LED will be on. High gas valve drops
out while high pressure switch is open because it is directly in series with the high pressure switch.
5.
When the thermostat W2 call ends and W1 remains (two stage thermostat), the control
de-energizes the high gas output and immediately changes inducer speed from high to low. With the
thermostat heating contacts open (single stage thermostat), the fl
ames extinguish immediately and the
induced blower stops after a 5 second post purge time.
6.
Blower off delay is handled by the ECM (Electronically Commutated Motor).
The control de-energizes the
ECM heat signal when the gas valve de-energizes, and starts a programmed soft stop (slowly ramp down)
delay period.
4.8 VARIA
TIONS
If your system includes air conditioning, your thermostat (supplied by the installer) will likely have two switches.
The fi
rst switch is the system switch. The switch settings usually include HEA
T , COOL, and OFF
. Some
thermostats have system switches which include HEAT,
COOL, AUT
O, and OFF . The system switch must be in
the HEAT
or AUT
O position for the furnace to run.
The second switch is the fan switch. It usually has settings of ON and AUT
O. The fan switch may be in either
position when using the furnace. If the fan switch is set to ON, the main blower will run continuously.
NOTE:
Soft start and soft stop features
available on ECM 2.3 models.
