Page 28
31-5000724 Rev. 0
•
Venting conditions change (affecting high and low
pressure switch operation)
•
Ramp down low fire switch check failed (calibration will
follow next call for heat)
•
The service technician (by pressing the push button
found on the integrated control until the control cycles
through to “Field Test Mode”)
The integrated control will do the following during
calibration:
1.
Verify both low pressure switch and high pressure
switch are open. If either are closed log error and end
calibration.
2.
Start inducer at a predetermined low RPM (1600).
Wait 7.5 seconds.
3.
Check low pressure switch, if open, increase RPM
by 250, wait 5 seconds. Repeat this step until low
pressure switch is closed.
4.
Decrease RPM by 50, wait 5 seconds and look for the
low pressure switch to open. Repeat this step until it
is open.
5.
Keep this RPM as RPM1.
6.
Increase RPM by 1250. Wait 5 seconds.
7.
Check high pressure switch, if open, increase RPM
by 250, wait 5 seconds. Repeat this step until high
pressure switch is closed.
8.
Decrease RPM by 50, check after 5 seconds. Repeat
this step until switch is open.
9.
Keep this RPM as RPM2.
10.
Calibration complete.
NOTE:
If after a successful calibration and a heat
call is present the integrated control will by-pass the
prepurge state and go straight into ignitor warm up.
After calibration, the integrated control stores the RPM1
and RPM2 values. The low fire (35%) and high fire (100%)
RPM points are calculated by adding margin values to the
RPM1 and RPM2 values.
The integrated control also initiates a low fire switch check
at the end of a normal heating cycle described below. If this
check fails the pressure switch calibration will follow on the
next call for heat.
1.
The inducer runs 15 seconds at the last firing rate
before the heat call ended.
2.
Inducer runs at 35% firing rate RPM (RPM1 + low
pressure switch open RPM margin value).
3.
If low pressure switch is open, set flag for calibration
on next call for heat. Turn inducer off until next call for
heat.
4.
If low pressure switch is closed move inducer speed to
RPM1. Allow 5 seconds for stabilization.
Finally, the switch interrupts the combustion process if
the condensate drainage system becomes blocked to the
point the condensate level builds up in the cold end header
box/ secondary coil or vent system.
If the switch assembly is to be replaced, replace the
entire assembly. Individual switch components cannot be
replaced.
The pressure switch is a safety shut-down control in the
furnace and must not be jumpered for any reason other
than troubleshooting.
WARNING
To troubleshoot the pressure switch, add a temporary
jumper. The unit will not fire with the switch jumpered.
Therefore, the pressure switch must be bypassed after the
combustion air inducer is activated. This will determine if
the pressure switch and furnace are operating properly.
However, this may not indicate if the sealed combustion
system is operating properly.
Figure 17.
bracket
low fire
high fire
Vent Calibration
The vent calibration sequence establishes furnace operating
parameters in a specific installation. The integrated control
runs the calibration and may be repeated as necessary
to maintain proper furnace operation. Prior to calibration,
all duct work (and returns) vent pipe and condensate trap
(primed) must be connected.
If calibration is successful the data is stored in memory and
will be used to determine furnace operation and maintain
parameters during heat call. If calibration is not successful,
the integrated control will proceed to a 5 minute delay and
signal the appropriate code. After the 5 minute delay the
calibration will be repeated 4 more times with a 5 minute
delay in between. If still unsuccessful after the 4 trials (total
5) the integrated control will go into a 1 hour soft lockout.
Calibration may be initiated by:
•
Initial call for heat
•
Cycling main power off / on and then call for heat
