TM_s-MEXT_ME28relC_00_12_19_EN
Technical manual
TRANSLATION OF THE ORIGINAL INSTRUCTIONS
89
The purpose of regulation is to keep the residual ∆P
constant when there is an increase in the counter-pressure, with reference to the following graph.
Figure 10-8:
Constant head fan operation curve
Starting from nominal work point (A), the increase in counter-pressure (due, for instance to a damper closing) causes a shift in the fan work point along the curve towards
point B, with the ensuing increase in pressure. The logic tries to restore the work point by decreasing 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
DC
signal increase / decrease).
•
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
.
10.5.4
Operation data display
From the main loop, it is possible to open the following masks that display the operation data of the two functions.
Target
02500 m3/h
Current
00000 m3/h
Status
Regulating…
Constant Capacity operation display mask.
Target
0020 Pa
Current
0000 Pa
Status
Regulating…
Constant Residual ∆P operation display mask.
