User Manual

Worcester Actuation Systems Series 75 Electric Valve Actuator FCD WCAIM2013-01 - 08/04
12
G. Heater and Thermostat
NOTE:
Heater and thermostat option requires no adjusting. If
defects are found, notify factory.
The thermostat will close/energize heater at ambient temperatures
below 70°F.
H. Drain/Breather (V53) Option (10-2375 Actuators)
If actuator is equipped with drain/breather at bottom of base,
actuator must be operated in an upright position for drain to
operate properly.
I. 4-75 Position Indicator
1. Description:
The 4-75 position indicator is designed to be used and
mounted with the standard Series 75 (Sizes 10-30), 120 VAC
actuator, with many of its standard options. Its output is suited
for 4-20 mA DC meter with 0-100% scale, which is not part of
the package. If properly calibrated, it indicates actuator shaft
position from close (0°, 0%) to open (90°, 100%).
It is combined with standard potentiometer, which supplies
information on shaft position. If feedback potentiometer
is required for other functions such as remote resistance
indication or a DFC17 Controller, a dual potentiometer has to
be used. Each potentiometer can serve only one function. See
potentiometer kit instructions (Part No. 66-09750), available
from your distributor/ supplier, for installation procedures, if
necessary.
2. Adjustment and Calibration:
NOTE:
If used with a DFC17 Controller, see DFC17 Installation,
Operation and Maintenance manual (part no. 66-14946) for
adjustment and calibration.
The feedback potentiometer has to be adjusted to obtain
proper resistance range. With the actuator either in the OPEN
(full CCW) or CLOSE (full CW) position, and power off, rotate
the face gear, thus turning the potentiometer shaft, until the
resistance between the white/black lead and the green lead
(actuator full CCW) or the white/black lead and the purple lead
(actuator full CW) respectively, as measured by ohmmeter, is
between 80 ohms and 90 ohms.
NOTE:
It is not necessary to loosen or remove face gear snap
ring to rotate gear, it is a friction fi t.
Power the actuator to the opposite position from where
resistance was measured.
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 above. If unsuccessful in getting proper resistance
readings, pot is defective and should be replaced.
To obtain proper 4-20 mA output, the indicator has to be
calibrated. Using an ammeter, connected to actuator Terminals
5 (positive) and 6 (negative), adjust the two potentiometers R4
and R5 on the board. With the actuator in the closed position
(0%), adjust R5 potentiometer (adjacent to the #4 etched on
the circuit board and closest to terminal block) to obtain 4 mA
on the ammeter. Move the actuator to the open position (100%)
and adjust R4 potentiometer (adjacent to the #20 etched on
the circuit board) to obtain 20 mA. Because adjustment of one
potentiometer affects the other, repeat the procedure several
times to obtain proper values.
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 a multiple of 360° from its original position or the
position indicator is removed from the actuator, the feedback
potentiometer will no longer be in calibration and must be
recalibrated.
3. Repair: In case factory repair is required, contact service
department, and request an RMA (Return Material Authoriza-
tion) number. After receiving new circuit board replace defective
board and return it back to factory with description of problem
and application.