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

Retracted

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

Siemens Industry, Inc.

Smart Infrastructure

1000 Deerfield Parkway

Buffalo Grove, IL 60089

USA

+ 1 847-215-1000

Your feedback is important to us. If you have comments

about this document, please send them to

sbt_technical.editor.us.sbt@siemens.com

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.

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