Siemens MT Series Owner's manual

Powermite™599
Technical Instructions
Document No. 155-314P25
EA 599-16
June 1, 2023
MT Series SSC81U Electronic
Valve Actuator, 24 Vac
Floating Control, Fail-in-Place
Siemens Industry, Inc.
Description
The Powermite 599 MT Series SSC81U electronic valve actuator requires a 24 Vac
supply to provide a floating control signal. This actuator controls Powermite 599 MT
Series valves with a 7/32-inch (5.5 mm) stroke and a threaded valve bonnet that fits the
actuator.
Features
•UL listed for plenum installations
•Direct-coupled installation without special tools (hand-tightened)
•Manual override
•Visual position indication
Application
The Powermite 599 MT Series SSC81U electronic actuator and MT Series valves are
used in closed loop heating and cooling applications. They are used in liquid and steam
(<5 psi) applications. The SSC81U actuator accepts a plenum cable or 3/8-inch flex
conduit connection.
Product Numbers
Table 1. Product Numbers.
Actuator
Operating Mode
Actuator Prefix
Code
SSC81U
Non-Spring Return
(Fail-in-Place)
259
Ordering a Valve
Plus Actuator
Assembly
To order a complete valve plus actuator assembly from the factory, combine the
actuator prefix code with the suffix of the valve product number. See Technical Bulletin
TB251, Powermite 599 Series MT Series Terminal Unit Valve and Actuator Assembly
Selection (155-306P25) for selection procedures.
To order an actuator only, use the product number.

Technical Instructions MT Series SSC81U Electronic Valve Actuator, 24 Vac Floating Control
Document Number 155-314P25
June 1, 2023
Page 2 Siemens Industry, Inc.
Warning/Caution Notations
WARNING:
Personal injury or loss of life may occur if you do not perform
a procedure as specified.
CAUTION:
Equipment damage may occur if you do not follow a
procedure as specified.
Specifications
Power requirements
Operating voltage 24 Vac 20%
Frequency 50/60 Hz 2 Hz
Power supply Earth ground isolating, Class 2,
24 Vac transformer
NOTE: Do not power more than
10 actuators with one
transformer.
Power consumption 0.8 VA
Functional operation
Running time 125 s 2% at 60 Hz
Nominal stroke 7/32-inch (5.5 mm)
Nominal force 67 lb (300N)
Stroke/signal relationship Linear
Agency certification
UL UL873 Listed
cUL Certified to CSA
C22.2 No. 24-93
Ambient conditions
Ambient temperature
Operation 41°F to 122°F (5°C to 50°C)
Transport and storage -13°F to 158°F (-25°C to +70°C)
Ambient humidity 0 to 90% rh (non-condensing)
Media temperature 35°F to 230°F (2°C to 110°C)
Physical characteristics
Wiring Connection Plenum cable or 3/8-inch flex conduit
Weight 1.1 lb (0.5 kg)
Dimensions See Figure 6.

MT Series SSC81U Electronic Valve Actuator, 24 Vac Floating Control Technical Instructions
Document Number 155-314P25
June 1, 2023
Siemens Industry, Inc. Page 3
Operation
A 24 Vac control signal to terminal Y1 extends the actuator shaft proportionately to the
length of time the signal is applied.
A 24 Vac control signal to terminal Y2 retracts the actuator shaft proportionately to the
length of time the signal is applied.
In the event of a power failure with no control voltage, the non-spring return SSC81U
will hold its last position.
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 4 and Figure 5)on
the top of the actuator to the 0position and verify the actuator
shaft completely retracts.
3. Connect a valve to the actuator, reapply power. The actuator will
return to normal operation.
Mounting and
Installation
Mount the actuator in one of the allowable positions shown in Figure 1.
Figure 1. 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.
Wiring
Use earth ground isolating, step-down Class 2 transformers. Do not use
autotransformers.
Determine supply transformer rating by summing total VA of all actuators used. The
maximum rating for a Class 2 step-down transformer is 100 VA.
Do not power more than 10 actuators by one transformer. (Use a 0.5-amp fuse on
secondary actuator.)
NOTE: Can be wired either neutral or hot switched.
CAUTION:
Terminals must be properly wired for correct function and full life of the
actuator.

Technical Instructions MT Series SSC81U Electronic Valve Actuator, 24 Vac Floating Control
Document Number 155-314P25
June 1, 2023
Page 4 Siemens Industry, Inc.
Wiring Diagrams
Figure 2. SSC81U Neutral Switching
Non-Spring Return.
Figure 3. SSC81U Hot Switching
Non-Spring Return.
Y2 Retracts actuator shaft
Y1 Extends actuator shaft
G System potential (hot)
Manual Override
For manual positioning, the override knob is
in the center of the position indicator. See
Figure 4.
Figure 4. Manual Override.
Start-up
Check the wiring and the position indicator.
See Figure 5.
Position Indicator
Output Shaft
0
Retracted
1
Extended
Figure 5. Position Indicator
(Shown in the 0 Position).
Troubleshooting
Check the wiring for proper connections.

MT Series SSC81U Electronic Valve Actuator, 24 Vac Floating Control Technical Instructions
Document Number 155-314P25
June 1, 2023
Information in this publication is based on current specifications. The company reserves the right to make changes in specifications and models as
design improvements are introduced. Powermite is a trademark of Siemens Industry, Inc. Other product or company names mentioned herein may
be the trademarks of their respective owners. © 2019-2023 Siemens Industry, Inc.
Siemens Industry, Inc.
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Buffalo Grove, IL 60089
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Document No. 155-314P25
Printed in the USA
Page 5
Service Kits
If the actuator is inoperative, replace the unit.
Disposal
The device is considered electrical and electronic equipment for
disposal in terms of the applicable European Directive and may not be
disposed of as domestic garbage.
•Dispose of the device through channels provided for this
purpose.
•Comply with all local and currently applicable laws and
regulations.
Dimensions
Figure 6. SSC81U Actuator Dimensions in Inches (Millimeters).
Service envelope
Minimum access space recommended:
8 inches (200 mm) above the actuator and 8 inches (200 mm) beside the terminal
cover.