User Manual

Worcester Actuation Systems Series 75 Electric Valve Actuator FCD WCAIM2013-01 - 08/04
8
Cam settings are as follows:
Switch 1 opens at 0°. Controls fi rst divert position.
Switch 2 opens at 180°. Controls secont divert position.
Switch 3 opens at 89°. Controls center-off position from
fi rst divert position.
Switch 4 opens at 91°. Controls center-off position from
second divert position.
NOTE:
Switches 1 and 2 and Cams 1 and 2 are standard.
Switches 3 and 4 and Cams 3 and 4 are center-off type.
Use cam spacer as needed to line up cam and switch.
B. Feedback Potentiometers (Single, Dual)
The potentiometer, as part of the Series 75 Actuator, is used to
obtain feedback representing the actuator’s position. It requires a
power supply, which may be furnished by the end user and/or by
optional devices such as a 4-75 (4-20 mA) Position Indicator or
AF17 Positioner.
A Dual Potentiometer is used with the DFP17, AF17 Positioners
or 4-75 Position Indicator when remote resistance indication
is required.
The Dual Potentiometer is required when both AF17 or DFC 17 and
4-20 mA position output options are to be used together, one pot
for each device.
Each pot can serve only one function. Remote resistance moni-
toring and an AF17, for example, cannot share a pot.
1. Adjusting Potentiometer:
NOTES:
Potentiometers are adjusted at factory. If readjusting is
necessary, follow instructions below.
Voltage limit of single pot or “B” pot of dual potentiometer is 30
volts maximum.
a. 10-3075 Actuator:
If not already installed, place the large face gear (12) over
the actuator shaft with the gear teeth down and secure with
snap ring (16) provided.
NOTE:
The face gear utilizes a friction fi t to the shaft. For
best results, wipe off any lubricant that may be on the shaft
before sliding on the face gear.
a
CAUTION:
Do not overstretch the snap ring, use
the minimum opening to allow snap ring to slip
over the gear.
b. Adjust the potentiometer spur gear (8) until there is approxi-
mately
1
⁄
1
⁄
1
16
⁄16⁄
" engagement with the large face gear. Tighten the
spur gear set screw (9). If necessary, you can slightly bend
potentiometer bracket to get proper engagement.
c. Rotate the face gear back and forth to ensure smooth and
easy operation of the potentiometer.
d. Important: FOR 90° VALVES: With the actuator in the
OPEN (full CCW) or CLOSED (full CW) position and power
off, rotate the face gear, thus turning the potentiometer
shaft until the resistance between the white/black lead
(terminal 11) and the green lead (terminal 10) or the white/
black lead (terminal 11) and the purple lead (terminal 12
respectively, as measured by an ohmmeter, is between 80
ohms and 90 ohms. (Refer to instruction sheets of options
that may have different pot lead locations and adjust-
ments, e.g., AF17 Positioner.)
NOTE:
It is not necessary to loosen or remove face gear
snap ring to rotate gear.
e. Power the actuator to the opposite position from where
resistance was measured.
f. At this position, with power off, measure the resistance at
the same terminals as stated above. The resistance reading
should be greater than 700 ohms. If not, then power
actuator back to original position and adjust pot again, if
necessary, as stated in paragraph d. above. If unsuccessful
in getting proper resistance readings, pot is defective and
should be replaced.
The feedback potentiometer is now adjusted for use in the
75 actuator.
IMPORTANT:
The feedback potentiometer is calibrated
for only one 90° quadrant of valve operation. If the output
shaft is repositioned to another 90° quadrant or if the
output shaft is rotated on a multiple of 360° from its
original position, the feedback potentiometer will no longer
be in calibration and must be recalibrated.