Scully ST-15 WX User manual

Scully ST-15 WX
Technical Manual
Multi-Point Liquid-Level Detection System
Scully Signal Company / Tel. [phone] / Fax. [phone] / 800 2 SCULLY (272 8559)
70 Industrial Way, Wilmington, MA 01887-3479, USA / [e-mail] / www.scully.com
MaxSafety®
SYSTEMS

ST-15-WX - Technical Manual
Table of Contents
General 4.
1.1 Function
1.2 Model Description
1.3 Power Requirements
1.4 Alarm Output
1.5 Control Contacts
1.6 Indicator Lamps
1.7 Controls
Installation 6.
2.1 Mechanical Installation
2.2 Electrical Connections
Operation 8.
Maintenance 9.
4.1 Front Panel Indicator Lamps
4.2 Dynacheck®Indicator LED
4.3 ST-15 Modules
4.4 Relays
4.5 Fuses
Diagram Appendix
5.1 DWG 21188 – Schematic ST-15-WX System 10.
5.2 DWG 61410 – Replacement Parts ST-15-WX3-12 11.
5.3 DWG 61413 – Field Wiring Diagram Models ST-15-WX3-4 12.
5.4 DWG 61415 – Field Wiring Diagram Models ST-15-WX5-8 13.
5.5 DWG 61419 – Field Wiring Diagram Models ST-15-WX9-12 14.

ST-15-WX - Technical Manual
General
Page 4.
1.1 FUNCTION
The ST-15C-WX series control units are multi-point liquid level alarm units. Typical applications are
for high and/or low level alarm in fixed storage tanks.
The Following is a listing of probe models that are compatable with the ST-15-WX:
The ST-15-WX control units can be mounted in any non-hazardous area and utlized oil tight
controls and indicators. Internal circuitry provides intrinsically safe (I.S.) output, for pobe
connections. This output is rated for Class 1, Div 1, Group D hazardous areas
1.2 Model Description
The number following the “WX” denotes the number of ST-15C Control Modules in the model.
Each module is referred to as a “channel” and can monitor one sensor. Thus, an ST-15-240-WX10
can monitor 10 probes.
The Scully part numbers for the various models are as follows:
Thermistors
Applicable Probes
Instant-On™
Two-Wire Optic
SP-M SP-TOM
SP-MU SP-IO
SP-MH
SP-MH
SP-BL
SP-BLU
SP-BLH (Heated Products)
Model Part Number
ST-15-115-WX3 07851
ST-15-115-WX4 07852
ST-15-115-WX5 07853
ST-15-115-WX6 07854
ST-15-115-WX7 07855
ST-15-115-WX8 07856
ST-15-115-WX9 07857
ST-15-115-WX10 07858
ST-15-115-WX11 07859
ST-15-115-WX12 07860
Model Part Number
ST-15-230-WX3 07800
ST-15-230-WX4 07801
ST-15-230-WX5 07802
ST-15-230-WX6 07803
ST-15-230-WX7 07804
ST-15-230-WX8 07805
ST-15-230-WX9 07806
ST-15-230-WX10 07807
ST-15-230-WX11 07808
ST-15-230-WX12 07809

Multi-Point Liquid-Level Detection System
General
Page 5.
1.3 Power Requirements
The ST-15C-WX units consume less than 20 watts of line power per channel exclusive of
controlled circuits and alarm devices. Models ST-15-115-WX operate from100-140 VAC,
50-60Hz mains power, Models ST-15-230-WX operate from 200-250 VAC, 50-60 Hz mains
power.
1.4 External Aalarm Output
A mains voltage alarm output is applied whenever any channel trips to the alarm position.
The alarm output is rated at 4 amps maximum current and is protected by an internal fuse.
When an alarm takes place, the alarm output line is energized and remains energized until either
the alarm condition is corrected or the alarm acknowledge switch is operated. Operating the
alarm acknowledge switch does not hinder subsequent alarms from other channels.
An alarm buzzer, internal to the enclosure is also included.
1.5 Control Contacts
A Single Pole Double Throw (SPDT) volt-free contact set is provided on each ST-15 control unit,
thus a contact is provided for each sensor. These contact sets are rated at 250 VAC, 5 amp
resistive and may be used to control valves, motor starters or other electrical devices.
These contact sets are accessed through the unit’s main terminal strip.
1.6 Indicator Lamps
1.6.1 Power Lamp
A green power pilot lamp indicates that mains power is being supplied to the units.
1.6.2 Alarm Indicator Lamps
A single alarm indicator lamp is supplied for each channel in the unit. The legend plates on
these lamps will have been engraved with customer-provided information (optional) identifying
the function of each channel. These lamps light when an alarm condition takes place and will
remain lit until the alarm condition is corrected. Acknowledging an alarm does not change the
status of the associated alarm indicator lamp.
1.7 Controls
1.7.1 Alarm Acknowledge Button
The ALARM ACKNOWLEDGE (silence) push button or optional key-operated acknowledge
switch will silence the audible alarm devices when operated. The alarm acknowledging circuits
reset automatically when the fault condition is corrected.
1.7.2 Test Push-Button
The test button causes all high level alarm points to trip to their alarm condition when operated.

ST-15-WX - Technical Manual
Installation
Page 6.
2.1 Mechanical Installation
The ST-15-WX control unit must be installed in a NON-HAZARDOUS AREA. Normally the unit is
installed in the control room of a storage tank arena. It may be installed outdoors in its
weather proof enclosure. Conduit entries must be properly sealed to keep water out of the
enclosure.
2.2 Electrical Installation
The most important thing to keep in mind when making electrical connections to the ST-15-WX
control unit is to keep the intrinsically safe wiring to sensors separated from power and controlled
circuit wiring. Separate conduit holes are provided and must be used to keep wiring separated.
THE IMPORTANCE OF MAINTAINING ABSOLUTE SEPARATION OF SENSOR (PROBE) LEADS
AND OTHER WIRING CANNOT BE OVEREMPHASIZED!
See wiring diagrams in the Appendix (Section 5.0) for the specific model(s).
2.2.1 Power Connections
Connect a source of main power to terminals 2 and 3 on Terminal Strip TB-1 inside the unit.
See wiring diagram in Appendix (Section 5.0) for the specific model(s). Make sure that voltage
matches the design voltage of the system.
Connect the earth lead to terminal 1 on TB-1
2.2.2 External Alarm Devices
Connect mains voltage alarm horns, bells or sirens to terminals 4 and 5 on TB-1.
Make sure the total connected load does not exceed 4 amps.
2.2.3 Control Device Connections
The rest of the terminals, terminal 6 onwards, provide a SPDT relay contact, for each of the sensors
as shown in the wiring diagram. Make sure that the connected loads do not exceed 5 amps
resistive per contact set and that sources for these devices are used to prevent damage to the
ST-15-WX equipment through field wiring shorts for failures of controlled devices. Fuses internal to
the unit do NOT protect the contacts.
2.2.4 Probe Connections
2.2.4.1 Two-Wire Probes
The wiring diagram shows connections from TB2 of a ST-15 control module to a
probe. When connecting to a 2-wire optic or thermister probe, the 680 Ω resister
(factory installed) on terminals G and W should be kept connected.
2.2.4.2 Three-Wire Probes
The wiring diagrams also show connections to 3-wire probe for heated products.
The 680 Ω resister installed between the G and W terminals must be removed.
It is suggested that the resisiter be retained for future use.

Multi-Point Liquid-Level Detection System
Installation
Page 7.
2.2.4.3 Probe Lead Wire Size
The following table should be used to determine the appropriate wire size for ST-15-WX
Control Module to sensor connections for distance between ST-15-WX and the sensor.
CAUTION: If sensor leads are extended beyond 2500 feet, please consult the factory for
specific wiring recommendations to prevent jeopardizing the intrinsically safe provisions of
the system.
Wire Size Feet (MM2) Maximum Run Length Feet (Meters)
#16 (1.5) 400 (120)
#14 (2.5) 700 (210)
#12 (4.0) 1000 (300)
#10 (6.0) 1600 (480)
#8 (10.0) 2500 (760)

ST-15-WX - Technical Manual
Operation
Page 8.
3.1 ST-15-WX control units are shipped with each channel set to provide high level alarming (alarm
output when liquid touches a probe). If your application requires alarm when a sensor becomes
“dry”, typical for low level sensing, consult the factory for wiring instructions.
When system power is applied, all high-level alarm channels will produce alarm outputs (red lamp
on and alarm buss energize) until their associated thermistor probes warm up. This will take
approximately 10 seconds. (Note: warm up time varies with ambient temperature of air surrounding
the probe) When a probe is “dry” and warmed up, the associated channel’s red lamp will go out.
Two-wire optic probes do not require any warm-up time.
The sensor is NOT a “switch”. The ST-15-WX control unit will not respond and indicate “dry” with
anything but a dry probe connected to its input terminals. Shorted or open probe circuits will not
cause the ST-15-WX Control Unit to go “permissive”.

Multi-Point Liquid-Level Detection System
Maintenance
Page 9.
4.1 Front Panel Indicator Lamps
These indicator lamps are changed by unscrewing the lens caps and replacing the bulbs beneath
them.
4.2 Dynacheck®Indicator LED
Each of the internal ST-15 control modules contains a Dynacheck®indicator lamp. (Scully part
number 27002). The lampwill flash once every few seconds when the ST-15 Control unit is
connected to a “dry” probe. The Dynacheck®indicator lamp is removed by pulling it straight out
of its socket. Burnout of the Dynacheck®indicator LED will not affect the performance of the
ST-15 module.
4.3 ST-15 Modules
The ST-15 control modules contain no field repacable components other than the Dynacheck®
indicator LED. The modules must be removed as a unit and returned to the factory.
Note: returns to the factory must be accompanied by an RMA number- The RMA number must be
obtained from Scully Signal Company
DO NOT ATTEMPT to service or adjust the ST-15-WX moduled without specific approval and
instructions fro Scully Signal Company.
4.4 Relays
Repace control relays only with equivalent types, making sure that the relays’ coil voltage matches
the system voltage.
4.5 Fuses
Do not replace fuse F1 and F2 with other than 5 amp slow-blow units.

ST-15-WX - Technical Manual
Diagram Appendix
5.1 DWG 21188 – Schematic ST-15-WX System
21188 Rev M
Page 10.