VDH Products PROBA, Инструкция по установке и эксплуатации

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VDH Products BV Document 063319 - version 3.12 Page: 33 of 78
1370 During alternative pressure fan control (analog output option 13 and 14, see parameter 6001..6004) the
parameters 1370..1374 are applicable. The principle of the alternative pressure fan control is according to
the following algorithm, see also Figure 4:
1) If the highest measured (control) temperature in the enabled zones is
within the temperature dead
band (around temperature setpoint), then the fan control is based on a pressure based PI controller.
The pressure based PI controller uses P1371 as P band and P1374 as I time. For analog output
option 13, Figure 5 is applicable, for analog output option 14, Figure 6 is applicable (with an other
control direction). Within the temperature dead band, the analog output value X is applied to the
analog output.
Note: The measured value of pressure sensor 2 (if present) is only used for alarms.
2) Within a transition band the value of the analog output is set to a value according to a linear curve
ranging from the value X up to 100% (10Vdc), see Figure 4.
Parameter P1373 states if the pressure based PI controller stops (freezes) or continues its
calculations of value X when the temperature dead band is leaved:
P1373 set to 0: The pressure based PI controller continues to calculate value X, also outside the
temperature dead band. This causes that within the transition band, the analog output also depends
on the measured pressure and pressure setpoint. (While the continued calculations can result in a
changed value X, which changes the 'slope' in the transition bands as drawn in Figure 4.)
P1373 set to 1: The pressure based PI control value X is frozen when the temperature dead band is
leaved. This causes that within the transition band, the analog output does not depend on the
measured pressure and pressure setpoint anymore. The calculation of the pressure based PI control
value X is restarted when the temperature dead band is entered again. Possible disadvantage of this
P1373 setting is that when the temperature dead band is entered again, a step change of the analog
output can occur. Especially when the difference between the frozen value X (fixed at leaving the
dead band) and the new calculated value X (at entering of the temperature dead band) is large.
3) If the highest measured (control) temperature in the enabled zones is outside the temperature dead
band and outside the transition bands, then the analog output is set to 100% (10Vdc).
4) The controls above (1..3) are overruled by: If fan 1 is switched off due to the fan settings according to
parameters 1301..1321 then the analog output is set to 0% (0Vdc).