Preferred FlexFit 110 - P4.1.1 Draft Control Option

4-78 Parameters
FlexFit – Linkageless Control – Revision 1.0
PREFERRED
UTILITIES MFG CORPORATION
PP
AA
RR
AA
MM
EE
TT
EE
RR
SS
• Adjustable Start Draft Option – On installations with excessively negative draft levels (very tall stack, oversized ID fan, badly
leaking stack damper) that are preventing the burner from lighting off, parameter "P4.3.1 Adjustable Start Draft Option"
allows the user to set different draft damper positions at the pilot trial for ignition and main trial for ignition states for each
fuel. When using this feature, the user must also set parameter "P4.3.2 Adj Start Draft SP".
To prevent lighting off under unsafe draft conditions, the FlexFit will initially position the draft damper to the value determined
by parameter "P4.3.3 Fuel 1 Adj Start Position" or "P4.3.4 Fuel 2 Adj Start Position", depending on which fuel is being red.
If, after this step, the measured draft still exceeds "P4.3.2 Adj Start Draft SP", the FlexFit will jog the draft damper open
until the draft drops below the setpoint. Once the burner is lit off, the FlexFit holds the draft damper at this position for a
time as determined by parameter "P4.2.9 Modulate Delay, Draft" and control reverts to normal.
• Modulate Delay – Parameter "P4.2.9 Modulate Delay, Draft" can be used to hold the draft damper at the purge position
(or adjustable start setpoint) for a set amount of time after the burner is released to modulate.
• Draft Cool-Down Delay – Parameter "P4.2.10 Cooldown Delay, Draft" can be used to hold the damper at the purge position
for an extended period after the burner has shut down. Some refractory-lined furnaces require extra cool-down after the
end of post purge.
• Low Draft Alarm – A low draft (high pressure) alarm can be congured by parameter "P4.1.5 Low Alarm SP, Draft". This
parameter determines the setpoint of the low draft alarm. Setting this parameter to +25.000 disables this alarm. To avoid
nuisance trips, "P4.1.6 Alarm Delay Sec, Draft" congures a time delay that must be exceeded before the FlexFit trips
the burner.
• Rate Limiters – Parameter "P4.2.4 Sec/90 Deg Damper Rate Limit, Draft" limits the speed of the draft damper (in seconds per
90° travel) to prevent over controlling. For electric servos, this value should be set to the same speed as the servo or slower.
Draft Control > Basic
P4.1.1 draFt control oPtIon
Menu > Setup > Draft Password Level: Engineer Restricted? Yes
Determines if draft control is used
Options: Disabled: No draft control is used
Floating Servo: Floating draft control with a servo actuated damper
Note If "Draft Control Option" is disabled, then all other draft control parameters are ignored.
P4.1.2 outlet daMPer Purge PoSItIon
Menu > Setup > Draft Password Level: Technician Restricted? Yes
This determines the draft damper position (in degrees) during purge.
Options: 30.00 to 200.00 [Default 80.00]
P4.1.3 draFt @ 4 Ma, xMtr cal
Menu > Setup > Draft Password Level: Technician Restricted? Yes
This determines the draft pressure/Vacuum that corresponds to 4 mA. For a fail-open design, this should correspond with the
high-pressure limit of the draft transmitter.
Options: -25.000 to 25.000 [Default 1.000]
Error Check The absolute value of P4.1.3 - P4.1.4 must be greater than 0.500.
P4.1.4 draFt @ 20 Ma, xMtr cal
Menu > Setup > Draft Password Level: Technician Restricted? Yes
This determines the draft pressure/Vacuum that corresponds to 20 mA. For a fail-open design, this should correspond with the
low-pressure limit of the draft transmitter.
Options: -25.000 to 25.000 [Default -1.000]
Error Check The absolute value of P4.1.3 - P4.1.4 must be greater than 0.500.
P4.1.5 low alarM SP, draFt
Menu > Setup > Draft Password Level: Operator Restricted? No
This determines the draft low alarm setpoint. If the measured draft is greater than the "Low Alarm SP, Draft" for longer than "P4.1.6
Alarm Delay Sec, Draft" seconds, the draft high-pressure alarm will be triggered.
Options: -25.000 to 25.000 [Default 25.000]
Note +25.000 disables this alarm.
Note
1" wc = 2.45 millibar.
The min-max ranges
accommodate millibars
and inches water column.