47
FIGURE 9.
Flue Temperature Limits
Note: The PPC4000 requires the flue temperature to be above the high limit or below the low limit
for 30 seconds before action takes place.
GAIN TERMS
O2 trim is performed using the current O2 level, the current saved target value and the boiler trans-
port delay. These terms are used in a PID algorithm to determine the amount of servo trim to be
applied.
1. P-GAIN is proportional gain and is the fractional part ranging from 0 to 1 (unity). Through the
user interface P-GAIN is expressed as 0 to 100%. The default value of P-GAIN is 6% or approxi-
mately 1/16. Increasing values of P-GAIN add amplification to the O2 trim and make the responsive-
ness more aggressive. Caution should be exercised when selecting P-GAIN as overshoot of the target
could occur.
2. I-GAIN is integral gain and defined as the reciprocal of Ti value in seconds ranging from 1 to 100
(subtracted from 101). The default value of 95 is 1/6 seconds. Selecting a value of 100 forces the
fastest possible integration time of 1 second. A value of 0 is a special case and disables the integrator.
A lower value of integration will slow down calculations and add time to reach the target value.
3. BOILER TRANSPORT DELAY can be defined as the derivative term when determining the
amount of servo trim to be applied. Any spikes or rapid changes in O2 levels caused by any distur-
bances will be filtered by the boiler transport delay term and prevent large changes in trim to be
applied. The default for boiler transport delay is 0 seconds and it is recommended this not be
changed if the O2 readings are relatively steady.
UNDERSTANDING O2 ERROR CODES
Upon detection of an error condition (lockout or warning) relating to the O2 probe the PPC4000 will
post to the display a singular message 'O2 FAULT eXX' on the HOME screen in place of the status
message. In the event of a lockout condition resulting from O2 levels being exceeded, flue tempera-
ture levels being exceeded or a fault in the O2 probe, the PPC4000 will revert to the FAULT HIS-
TORY menu with the details of the lockout described. For both lockout and warning events, the
200
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700
0
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100
De
g
re
e
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Firing
Rate
Zone
Flue
Temp
Flue
Temp
Lo
Flue
Temp
Hi
Acceptance
