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At each profile setpoint the target value is saved to interim memory by first using the MDFY key to
position the air or fuel servo to their appropriate positions and pressing the SAVE key. After a suffi-
cient wait time to achieve a reliable O2 reading the NEXT key is pressed to save the target value to
the setpoint table and move forward to the succeeding profile setpoint.
Profile setpoint pHigh is saved after waiting sufficient time to achieve a reliable O2 level reading and
then pressing the C-MODE key to exit commissioning. Pressing the C-MODE key saves all profile
setpoint data to permanent memory and defines the last setpoint entered as the high fire or 100%
modulation point.
You cannot manually modify the O2 concentration under the commissioning/adjust ratio screen. A
new O2 value is stored when any servo position is modified for the currently selected commissioning
point. The O2 value that is stored is the current O2 value at the time that the new position is saved.
Make sure the O2 concentration is stable and it is within the expected window before moving on to
the next commissioning point. During times that commissioning or adjust ratio needs to be reviewed
without affecting the saved O2 target levels, simply pressing the NEXT or BACK key will move to
the next or previous setpoint without affecting the saved O2 target level for that previously commis-
sioned profile setpoint.
OPERATION WITH O2 TRIM
With O2 trim enabled, if the firing rate changes by an amount of 30% or more, trim will be inhibited
until the following conditions occur:
1.
The air servo reaches its destination.
2.
O2 below target if direction of travel is low fire to high fire.
3.
O2 above target if direction of travel is high fire to low fire.
4.
O2 within dead band about target.
5.
O2 level stable - stable being steady reading plus/minus 0.2%.
6.
Servos stop moving for 20 seconds regardless the O2 level.
The trim servo will never move the maximum range of the trim limit in one adjustment.
Inside the dead band, 0.2%, O2 trimming is inhibited.
Note: Status of O2 trim can be verified by hitting the HOME key and reviewing the top line. If O2
trim is active, the top line should read AUTO(t). If O2 trim is not active, the top line should read
AUTO.
Trim Limit Test
To test the setting of the trim limit selected during O2 SETUP, it is suggested the user enter adjust
ratio mode (O2 trim becomes disabled), move to each profile setpoint and move the trim servo to its
maximum and minimum positions defined by the trim limit for that setpoint. Refer to rule shown in
section SETTING TRIM LIMITS. The purpose of this test is to insure that no hazardous conditions
(high CO levels) exist at the extreme positions of the trimmed servo. The user should be aware that
to move the trimmed servo the MDFY and SAVE keys must be used and by pressing the NEXT or
BACK key when done testing with this particular setpoint, the current O2 level will be saved as the
target for this profile setpoint. The user should ensure the servos are moved back to their originally
commissioned position to get back the original target O2 level before pressing the NEXT or BACK
key.
Process Control
A key function of the PPC4000 is to maintain the process control variable setpoint. In the ADJUST
SETPOINT menu setting a small value of P-BAND and high value of INTEGRAL could cause large
and unnecessary swings in the firing rate and subsequently servo motors. It is during these large
swings in firing rate that should be avoided when using O2 trim. The O2 trim algorithm will be con-
stantly chasing the target and if the swings are large enough, be inhibited during these large changes.
During commissioning and adjust ratio, O2 trim is not enabled.
