Technical Instructions
MT Series SSC Electronic Valve Actuator, 24 Vac Floating (3-Position) Control
Document Number 155-314P25
August 1, 2007
Page 4
Siemens Building Technologies, Inc.
Operation, Continued
CAUTION:
A valve must be connected to the actuator before applying power.
If applying power to the actuator when a valve is not connected, the
actuator will respond to a control signal and the shaft will extend until it
reaches its maximum end stop. Thereafter, it will not respond to any
signal. If this occurs:
1. Disconnect power.
2. Turn the manual position indicator (See Figure 7 and Figure 8
)
on
the top of the actuator to the 0 position and verify the actuator
shaft completely retracts.
3. Connect a valve to the actuator, reapply power. The actuator will
return to normal operation.
Calibration Stroke
The SSC81.5U writes its calibration stroke parameters to nonvolatile memory on the
first startup of the actuator. Successive startups bypass the calibration stroke unless the
memory is manually cleared. If installing the actuator on a different valve (such as on a
replacement valve), manually clear the calibration stroke from memory as follows:
1. Remove the terminal cover using a Phillips
head screwdriver.
2. Locate hole on the circuit board shorting
bars.
3. Insert and gently twist a flat-blade
screwdriver to electrically connect the
shorting bars (Figure 2
)
. The SSC81…
then performs a new calibration stroke.
4. Secure the terminal cover back in place.
EA1155R1
WIRING TERMINAL
WITH REMOVABLE
TERMINAL BLOCK
Shorting
Bars
TERMINAL
COVER
AND SCREWS
Figure 2. Manually Clearing Calibration
Stroke from Memory.
Mounting and
Installation
Mount the actuator in one of the allowable positions shown in Figure 3.
EA0791R2
Figure 3. Mounting Position.
When mounting the actuator in a plenum, the proper cable must be attached to meet
local codes. Allow 8 inches (200 mm) above the actuator and 8 inches (200 mm) behind
the cable for service.