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When configuring the unit the project flow value and the number of fans in the unit are entered.
The programme also requires that the fan flow is never less than the set rated flow.
The parameters entry mask is under the "Fan" menu accessible through the "Service" password.
The purpose of regulation is to keep the flow rate constant when there is an increase in the loss of load, with reference to the
graph below.
Starting from nominal work point (A), the increase in load loss (due, for instance, to clogged filters) from P1 and P2 causes a
shift in the fan work point along the curve towards point B, with the ensuing capacity decrease. The logic tries to restore the
work point by increasing the speed and move back towards work point C.
To avoid continuous speed adjustment without giving the fan time to adjust to the new speed value and consequently not
allowing the pressure transducer to measure the new differential pressure value, there is a "scan time" that sets the time between
the two fan signal variations.
The EC control parameters are under the "Fan" menu, accessible through the "Service" password.
The default values are are the following:
•
scan time = 60 sec;
•
step voltage = 10 (corresponds to a 0.1V
•
hyst flow = 25
•
Fan modulation delay = 120 sec.
The Fan modulation delay is used whenever the unit is started in order to allow the fan to start. Once this time elapses, speed
adjustment begins.
This parameter is in the "Regulations" menu that can be accessed with the "Service" password.
Version 38
Figure 11-4: constant flow rate fan operation curve.
signal increase / decrease).
DC
160
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