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Powermite 599 Series
MT Series SSC Electronic
Valve Actuator, 24 Vac
3-Position (Floating) Control
Technical Instructions
Document No. 155-314P25
EA 599-16
May 24, 2005
Description
Features
Application
Product Numbers
EA1157R1
The Powermite 599 Series MT Series SSC81U and SSC81.5U electronic valve
actuators require a 24 Vac supply to provide a 3-position (floating) control signal. These
actuators control Powermite 599 MT Series valves with a 7/32-inch (5.5 mm) stroke
and a threaded valve bonnet that fits the actuators.
• UL listed for plenum installations
• Direct coupled installation without special tools
• Manual override
• Visual position indication
The Powermite 599 Series MT Series SSC81… electronic actuators and MT Series
valves are used in heating and cooling applications. They are used in liquid and steam
applications that require an actuator that delivers a minimum of 67 lbs (300 N) nominal
force. The SSC81 series accepts plenum cable or 3/8-inch flex conduit connection.
Table 1. Product Numbers.
Actuator Operating Mode
Actuator Prefix
Code
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.
SSC81U Fail-in-Place 259
SSC81.5U Fail-Safe 260
Siemens Building Technologies, Inc.
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Technical Instructions MT Series SSC Electronic Valve Actuator, 24 Vac 3-Position (Floating) Control
Document Number 155-314P25
May 24, 2005
Specifications
Operating voltage 24 Vac ±20%
Power requirements
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.
SSC81U power consumption 0.8 VA
SSC81.5U power consumption 3 VA at ultra cap load,
2 VA at normal drift
Control characteristic
Control Signal
Y2 Retracts actuator shaft
Y1 Extends actuator shaft
G System potential
G0 (SSC81.5U only) System neutral
Functional operation
Running time
SSC81U 150 s ±2% at 50 Hz
125 s ±2% at 60 Hz
SSC81.5U 125 s ±2% at 50/60 Hz
Fail-safe, SSC81.5U only (Figure 1, ) ≈ 30 s
Nominal stroke 7/32-inch (5.5 mm)
Nominal force 67 lb (300N), +20%, -0%
Stroke/signal relationship Linear
Capacitor charge time (Figure 1 ) max. 180 sec
Fail-safe (SSC81.5U only) Non-mechanical, electronic return fails
to stem up (0 position)
Agency certification
UL UL873 Listed
cUL Certified to Canadian Standard
C22.2 No. 24-93
Ambient conditions
Ambient temperature
Operation 41°F to 122°F (5°C to 50°C) with
15 psi steam media
Transport and storage -13°F to 158°F (-25° C to +70°C)
Ambient humidity 0 to 90% rh (non-condensing)
Medium temperature 41°F to 248°F (5°C to 120°C)
Physical characteristics
Wiring Connection Plenum cable or 3/8-inch flex conduit
Weight
SSC81U 1.1 lb (0.5 kg)
SSC81.5U 1.3 lb (0.6 kg)
Dimensions See Figure 8
Page 2 Siemens Building Technologies, Inc.
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MT Series SSC Electronic Valve Actuator, 24 Vac 3-Position (Floating) Control Technical Instructions
Document Number 155-314P25
May 24, 2005
Service Kits
EA0851R1
EA1156R1
EA1138R1
EA0847R1
3mm
4 224 5618 8 Visual Position Kit to
replace one indicator and two gears.
(Previous version.)
4-115-5564-8: Kit contains:
- Terminal cover
- Cover screws-2 (not shown)
- Tailpiece
- Tailpiece screw-1 (not shown)
- Cable lock
- Terminal block-3
EA1162R1
EA1138R1
EA1138R1
4-116-5608-8: Kit contains:
- Terminal Cover
- Cable lock
- Cover screw- 1 (not shown)
Operation
EA0850R1
EA0851R1
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 SSC81U fails-in-place and
holds its last position.
In the event of a power failure, the SSC81.5U returns to its normal fail-safe position.
The SSC81.5U includes an electronic return mechanism that functions a s follows. See
Figure 1.
• At power-up (t0), a capacitor must
charge to its maximum capacity
(Max, tc). This will take a maximum
of 180 sec, during which time no
actuator movement occurs.
• Once the capacitor is fully charged
(tc), normal actuator operation
occurs.
• If a subsequent power failure occurs
(tn) of greater than 5 sec, the
TIME TO
CHARGE
Max
CHARGE
0
t0 tc tn t
MAX
EA0798R2
180s.
Figure 1. SSC81.5U Electronic Fail-Safe
NORMAL
ACTUATOR
OPERATION
TIME
Mechanism.
TIME TO
DISCHARGE
MAX
30s.
ACTUATOR
d
capacitor discharges (td) and the
actuator returns to its normal fail-safe
position.
POSITION
Siemens Building Technologies, Inc. Page 3
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Technical Instructions MT Series SSC Electronic Valve Actuator, 24 Vac 3-Position (Floating) Control
Document Number 155-314P25
May 24, 2005
Operation, Continued
CAUTION:
Before applying power, make certain a valve is connected to the
actuator.
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, turn the manual position indicator (See Figure 6 and
Figure 7) on the top of the actuator to the 0 position and verify the
actuator shaft retracts completely. Disconnect power. Connect a valve
to the actuator, reapply power, and the actuator will return to normal
operation.
Calibration Stroke
Mounting and
Installation
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.
TERMINAL
COVER
AND SCREWS
WIRING TERMINAL
WITH REMOVABLE
TERMINAL BLOCK
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
Figure 2. Manually Clearing Calibration
Stroke from Memory.
Shorting
Bars
Mount the actuator in one of the allowable positions shown in Figure 3.
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.
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EA0791R2
Figure 3. Mounting Position.
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MT Series SSC Electronic Valve Actuator, 24 Vac 3-Position (Floating) Control Technical Instructions
Document Number 155-314P25
May 24, 2005
Wiring
Wiring Diagrams
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.
CAUTION:
Terminals must be properly wired for correct function and full life of the
actuator.
CONTROLLER
NEUT
EA0795R1
ACTUATOR
Y2
Y1
G
24
Vac
EARTH GROUND
ISOLATING CLASS 2
TRANSFORMER FOR
24 Vac POWER
120 Vac
Y2…Retracts actuator shaft
Y1…Extends actuator shaft
G…System potential
Figure 4. SSC81U (Fail-in-Place)
Wiring.
0
1
CONTROLLER
EARTH GROUND
ISOLATING CLASS 2
24 Vac TRANSFORMER
EA0796R3
24 Vac
ACTUATOR
Y2
Y1
G
G0
NEUT
120 Vac
Y2…Retracts actuator shaft
Y1…Extends actuator shaft
G… System potential
G0…System neutral
Figure 5. SSC81.5U (Fail-Safe) Wiring.
0
1
0
Manual Override
For manual positioning, the manual
override knob in the center of the position
indicator per Figure 6.
EA1161R1
COUNTER
CLOCKWISE
RETRACTS
SHAFT
A
AB
CLOCKWISE
B
EXTENDS
SHAFT
Figure 6. Manual Override.
Siemens Building Technologies, Inc. Page 5
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Technical Instructions MT Series SSC Electronic Valve Actuator, 24 Vac 3-Position (Floating) Control
Document Number 155-314P25
May 24, 2005
Start-up
Check the wiring and the position indicator
(Figure 7).
1
Troubleshooting
Service Kits
Dimensions
Position Indicator Output Shaft
0 Retracted
1 Extended
Check the wiring for proper connections.
If the actuator is inoperative, replace the unit.
3.5
(89)
.85
(21,6)
0
EA1158R1
Figure 7. Position Indicator
(Shown in 0 Position).
4.4
(110,8)
2
(48)
1
0
4.5
(115,1)
5.5
EA1159R1
(140)
Figure 8. SSC Actuator Dimensions in Inches (Millimeters).
Service envelope
Minimum access space recommended:
8 inches (200 mm) above the actuator and beside the terminal cover.
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. Other product or company names mentioned herein may be the trademarks of their respective owners.
© 2005 Siemens Building Technologies, Inc.
Siemens Building Technologies, Inc.
1000 Deerfield Parkway
Buffalo Grove, IL 60089-4513
U.S.A.
Your feedback is important to us. If you have
comments about this document, please send
them to SBT_technical.editor@siemens.com
Document No. 155-314P25
Country of Origin: US
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