ATR 421 - User manual 25
8.6.2 Gas – Management mode
Gas kilns management assigns the outputs commands according to the type
of the step: during rising and holding steps the fans are switched on and
when the setpoint value is greater than the process value burners are also
switched on. After elapsing of the time set on parameter 39 bu.s.t. since
burners switch-on, controller considers the ame lighted and so (if neces-
sary) it updates the setpoints (as the process value could have decreased in
the meantime).
If the temperature value is greater than the setpoint introduced on parame-
ter 40
t.s.o.b. burners switch o , they will restart when temperature goes
down again; parameter 41 b. HY. de nes burners command hysteresis.
For falling steps, if the temperature value is lower than the setpoint on para-
meter 42 t.s. o.f. fans will switch o .
Output management is also di erent according to the selection on parame-
ter 18 act.t. Below all available options:
• GAS: during falling steps burners stay o .
• G. f.S. (Gas Falling Steps) (GID). During falling steps burners work in ON/
OFF mode: the servo valve regulates air ow for cooling and it is always
closed when burners are switched on.
• G. f.S.s. (Gas Falling Steps Servovalve) (GIDS). During falling steps gas mo-
dulation is done by servo valve: management is the same as for rising and
holding steps.
If a feedback valve is used, parameters 24 L.L. o . p. and 25 u.L.o.p. determina-
te max. and min. limit for valve opening when burners are switched on: with
burners switched o , valve will open and close totally.
8.7 Feedback valve
ATR421 allows to connect to AI2 the feedback potentiometer of a motorized
valve. Remember to calibrate the potentiometer to allow the controller esta-
blish precisely valve limits. After valve (“open” pins 3-5 and “close” pin 4-5)
and the potentiometer (pins 15-16) have been connected, select c. uAL. on
parameter 1 c.out and Po. cA. on parameter 44 FE.Po .: exiting con guration
mode, controller will automatically start to open and close the valve in order
to x limits.
Once this procedure ends, controller selects en. on parameter 44 FE.Po . If a
new potentiometer procedure is required, it will be necessary to set Po . ca.
on parameter 44 FE.Po.
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