11
SERVOMOTOR
The servomotor gives simultaneous regulation of the air
damper through the variable cam profile 4)(F) and the
gas butterfly valve.
It rotates by 130° in approx. 35 s.
The factory settings must not be changed for the first fir-
ing, just check that they comply with the details below.
To open the servomotor, remove the screws and pull the
cover outward, fig. (A).
CAMS AND TRIM POTENTIOMETERS FUNC-
TIONS
Cam 1:
130°
Limits rotation towards maximum for gas.
Cam 2:
0°
Limits rotation towards minimum, air damper closed on
stand by.
Cam 3:
20°
Limits gas ignition position.
Cams 4 - 5 - 6 - 7 - 8: not used
Trim potentiometer MAX
Limits maximum modulation.
It must be set near the stroke end (cam 1) to exploit as
far as possible the variable profile cam and maximum
opening of the gas butterfly valve.
Trim potentiometer MIN
Limits minimum modulation.
It must be set near the stroke end (cam 2) to exploit as
far as possible the variable profile cam.
Trim potentiometer POS
Limits an intermediate operating position between MAX
and MIN, supplying power to the "P" terminal in the ser-
vomotor (through an external command). This function
cuts out any external signals.
Note
Using the slide switch to select MAX or MIN, the servo-
motor goes into the position for the respective settings of
the MAX and MIN TRIM POTENTIOMETERS.
When the settings are complete, place the slide switch
on OPE.
(D)
(F)
(E)
(C)
1 Servomotor
2 Graduated sector for gas
butterfly valve
3 Index for graduated sector 2
4 Adjustable profile cam
5 Adjustment screws for cam
starting profile
6 Adjustment fixing screws
7 Adjustment screws for cam
and profile
Slide switch
Trim potentiometers
Position jumpers
D2277
D2585
D2594
D2593
(A)
(B)
NO
Figure above shows how the servo-
motor is released to manually check
there is no binding though its motion.
Don’t release the button indi-
cated in this figure: the syn-
cronization of the cams
made in factory would be
changed.
YES
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