Introduction
ABB Zenith Transfer Switches provide a continuous source of power for lighting and other critical loads by automatically transferring from source 1 power to source 2 power when source 1 voltage falls below preset limits. Voltage sensing and system control is performed via a state-of-the-art microcontroller located on the cabinet door. It is designed to give highly accurate control of the transfer switch system.
All ABB Zenith transfer switches are designed for use on emergency or standby systems, and are rated for total system or motor loads. Transfer switches are UL Listed under Standard 1008 and CSA Certified under Standard C22.2 No. 178 and IEC Listed under Standard 947.
NOTES: A protective device such as a molded case circuit breaker or fused disconnect switch MUST be installed on both sources of incoming power for circuit protection and as a disconnection device. All references made within this manual about the term "S1" or "Source 1" relate to a Normal Power Source. All references made about the term "S2" or "Source 2" relate to an Emergency or Alternative Power Source.
Safety and Installation
DANGER: HAZARDOUS VOLTAGE (Can Cause Severe Injury or Death)
Turn OFF all power before installation, adjustment, or removal of transfer switch or any of its components.
The safe operation of your switch is ABB Zenith's focus. The proper storage, installation, operation and maintenance will help increase the life of the switch.
CAUTION: Due to hazardous voltage and current, ABB Zenith recommends that an ABB Zenith Certified technician or a qualified electrician must perform the installation and maintenance of the switch.
Equipment Inspection and Storage
Once you have received the transfer switch, inspect it for any damage. This includes damage to the enclosure, power panel, control panel and wiring harness. If any damage is found or suspected, file a claim as soon as possible with the carrier and notify the nearest ABB Zenith representative.
Before installation, if it is necessary, store the transfer switch in a clean dry place, protected from dirt and water. Provide ample air circulation and heat, if necessary, to prevent condensation.
Table 1: Storage and Operating Conditions
| Storage Temperature | Operating Temperature (Ambient) | Humidity |
|---|---|---|
| -30°C to +75°C (-22°F to +167°F) | 40-400 AMP (molded shell): -20°C to +65°C (-4°F to +149°F) 40-4000 AMP (all other frame and panel types): -20°C to +60°C (-4°F to +140°F) | 5% to 95% (non-condensing) |
WARNING: Do not use a blower since debris may become lodged in the electrical and mechanical components and cause damage.
Final Equipment Inspection
Prior to energizing the transfer switch:
- Remove any debris incurred, with a vacuum, due to shipment or installation.
- Verify that all cabled connections are correct and that phase rotation of both sources match.
- Check engine start connections.
- Verify the correct connection of all control wires.
- Check settings of all timers and adjust as necessary.
- Adjust any optional accessories as required.
- Check the lug torque values of the power connections. NOTE: Lug torque values are specified in the power panel manual.
- Make sure that all covers and barriers are installed and properly fastened. NOTE: Power panels ship from ABB Zenith in Source 1 Position.
Each ABB Zenith transfer switch is factory wired and tested. A complete information package is furnished with each switch which includes:
- Sequence of operation.
- Description and operation of all accessories supplied.
- Power panel connection diagram and schematic.
- Description and identification of all customer field connections.
Installation of ABB Zenith transfer switches includes:
- Mounting the transfer switch cabinet.
- Connection of Source 1, Source 2, and Load cables or bus bars.
- Connection of external control circuits as required.
Installation
DANGER: HAZARDOUS VOLTAGE (Can Cause Severe Injury or Death)
Turn OFF all power before installation, adjustment, or removal of transfer switch or any of its components.
Engine Start Control Connections
The engine-start terminals are clearly identified by a label on the microcontroller backplate. In the case of manual transfer switches, or in other applications not requiring the microprocessor, clearly marked terminal blocks are provided in the upper left corner of the control panel for the engine start control wires.
Figure 2 shows the location of engine start connections for Bypass Isolation Transfer Switch. Figure 5 (pg. 6) shows location of engine start connections for Automatic Transfer Switch.
Terminals for field connections to the A3 Source 2 auxiliary contacts and the A4 Source 1 auxiliary contacts are also provided. These terminals are clearly marked and appear on the side of the power panel. On 400 amp metal frame units these terminals appear on the bracket above the operator handle.
Figure 1 depicts a P Relay (Engine Start) with contact rating of 10 Ampere at 120VAC or 28VDC (Gold plated).
Initial Energization
Before proceeding, refer to the information package supplied with the ATS and read and understand the information on all accessories provided.
- Unlock the enclosure.
- Open the enclosure.
- Verify the correct system voltage. The equipment rating nameplate on the transfer switch lists the voltage.
- Close Source 1 circuit breaker. The controller will illuminate the Source 1 Available LED if proper voltage is sensed.
- Verify the phase to phase voltages at Source 1 line terminals.
- Close Source 2 circuit breaker.
- Start the generator's engine. The controller will illuminate the Source 2 Available LED when preset voltage and frequency levels are reached.
- Verify the phase to phase voltages at Source 1 line terminals.
- Verify that the phase rotation of Source 1 is the same as the phase rotation of Source 2.
- Shut down the generator's engine.
- Place the starting control in the Automatic position.
- Complete the visual inspection of the transfer switch.
- Close the enclosure.
- Lock the enclosure.
Figure 3 illustrates a typical nameplate showing Serial Number, Rating, Volts, Hz, Amps, Phase, System Volts, and Model Number.
CAUTIONS: Certain accessories, per specific schematics, can inhibit automatic transfer. Engine Gen-Set could start when engine control wires are attached.
Installation (cont'd)
Initial Energization (cont'd)
After all options and accessories are checked and verified, follow these steps to set up the ATS. Refer to the Entelli-Switch 250 display (Figure 4). The annunciation LEDs illuminate to indicate (1) source availability, (2) ATS position, and (3) Entelli-Switch 250 control function (timing).
Figure 4 shows the LCD and keypad of the Entelli-Switch 250. The LCD displays status like 'S1 OK', time, and date. The keypad includes menu buttons (MORE, CFG, TEST, SET) and numbered buttons (1-4).
- Unlock the enclosure.
- Open the enclosure.
- Place the Disconnect Switch in the Inhibit. This step is only performed if the "DS" Option was purchased.
- Close the external (up-stream) Source 1 circuit breaker. Source 1 Available and Source 1 Position LED's will illuminate. If Source 1 Available LED does not illuminate, verify that Source 1 Voltage is above the preset restore value.
- The Gen-Set will start and run while the Source 2 stop Delay Timer is timing.
- Close the External (up-stream) Source 2 line circuit breaker.
- Start the engine generator in MANUAL mode. When the voltage and frequency reach preset values, the Source 2 Available LED will illuminate.
- Verify the phase to phase voltages at Source 2 line terminals.
- Verify that the phase rotation of Source 2 is the same as the phase rotation of Source 1.
- Shut down the generator's engine. (Place in Automatic Mode.) Source 2 Available LED will turn off. The engine generator will continue to run for the duration of the Source 2 Stop Delay Timer.
- Place the disconnect switch to ENABLE.
- Complete the visual inspection of the transfer switch.
- Close the enclosure.
- Lock the enclosure.
WARNING: When performing a hi-pot or dielectric test on the power section, DISCONNECT the control panel plugs from the microprocessor to avoid potential damage.
Control Connections
Figure 5 illustrates the control connections on the printed circuit board (PCB). It shows Engine Start Connections, Input/Output Connectors to I/O Modules, Network Connector, Clock Program Backup Battery (with instruction to remove protective strip), and connections labeled 'To Power Panel' and 'To R/T Box'.
A complete information package is furnished with each transfer switch including a complete connection diagram and schematic which details all necessary control circuit field connections.
The engine start control wires connect to the engine start relay terminals located to the left of the microprocessor. Figure 5 shows the location of these terminals.
The terminals are clearly identified by a label on the microcontroller backplate. In the case of manual transfer switches, or in other applications not requiring the microprocessor, clearly marked terminal blocks are provided in the upper left corner of the control panel for the engine start control wires.
Entelli-Switch 250 Controller
Overview
The Entelli-Switch 250 Controller consists of two major assemblies:
- The Microprocessor: Contains the Entelli-Switch 250 Board (Customer Input and Output for system interface) and the LCD and Keypad located on the exterior of the door. The board supports I/O accessories such as engine start relay output, pre-signal, transfer inhibit, remote test, and network interface. The LCD/Keypad provides user access to source availability LEDs, transfer switch position LEDs, timer countdown, event reporting, and settings/configuration functions.
- The Controls Power Supply (CPS): Contains transformers that drop line voltage to a control level for controller input and SCR inputs, isolating the MX250 from line voltage and protecting it from transients.
Figure 6 shows the I/O Interface, Engine Start Relay P, Entelli-Switch 250 Board, Battery Strip and Access Code Label, and the CPS.
Figure 7 shows the Entelli-Switch 250 controller with its display and keypad.
LCD & Keypad
Options are accessible through the LCD and keypad. Scrolling through the SET and CFG menus displays option descriptions. The SET menu is used for time and voltage settings, while the CFG menu is for turning options ON or OFF. An access code is required to make changes.
The factory-set six-digit access code is located on a white label on the back of the unit. The Entelli-Switch 250 supports various logic options downloaded at the time of manufacture.
Figure 8 illustrates the LCD and Keypad interface. It labels the Source 1/2 Available LEDs (Green/Red), Source 1/2 Position LEDs (Green/Red), the LCD screen displaying current time, day, and date, and the keypad buttons (MORE, CFG, TEST, SET) and numbered buttons (1-4) with their associated functions indicated by text above them on the LCD.
User Setting for Voltage & Frequency
This section details user settings for voltage and frequency parameters for standard 3-phase sensing on 3 and 4 pole units.
Source 1 Settings
- Under Voltage "Restore": Minimum acceptable voltage for transfer to Source 1. Default: 90%. Range: 85% to 100%.
- Under Voltage "Fail": Low voltage threshold. Default: 80%. Range: 75% to 98%. "Fail" must be a minimum of 2% below "Restore".
- Under Frequency "Restore": Minimum acceptable frequency for transfer to Source 1. Default: 95%. Range: 90% to 100%.
- Under Frequency "Fail": Low frequency threshold. Default: 90% (5 seconds minimum). Range: 88% to 98%. "Fail" must be a minimum of 2% below "Restore".
- Over Frequency "Restore": Minimum acceptable over frequency for re-transfer to Source 1. Default: 102%. Range: 102% to 104%. "Restore" must be a minimum of 1% below "Fail".
- Over Frequency "Fail": Maximum acceptable over frequency. Default: 105%. Range: 103% to 105%.
Source 2 Settings
- Under Voltage "Restore": Minimum acceptable voltage for transfer to Source 2. Default: 90%. Range: 85% to 100%.
- Under Voltage "Fail": Low voltage threshold. Default: 80%. Range: 75% to 98%. "Fail" must be a minimum of 2% below "Restore".
- Over Voltage "Fail": Maximum acceptable over voltage. Default: 110%. Range: 105% to 110%.
- Over Voltage "Restore": Minimum acceptable over voltage threshold for transfer to Source 2. Default: 105%. Range: 103% to 105%. "Restore" must be a minimum of 2% below "Fail".
- Under Frequency "Restore": Minimum acceptable frequency for transfer to Source 2. Default: 95%. Range: 90% to 100%.
- Under Frequency "Fail": Low frequency threshold. Default: 90% (5 seconds minimum). Range: 88% to 98%. "Fail" must be a minimum of 2% below "Restore".
- Over Frequency "Fail": Maximum acceptable over frequency. Default: 105%. Range: 103% to 105%.
- Over Frequency "Restore": Minimum acceptable over frequency threshold for re-transfer to Source 2. Default: 102%. Range: 102% to 104%. "Restore" must be a minimum of 1% below "Fail".
Accessory Group Packages
Table 2 lists various accessories and indicates their inclusion in different group packages (STDS, EXES, CONS, SENS, SPES, PSGS).
Accessory Definitions
This section defines various accessories available for the Entelli-Switch 250 controller, including:
- 6P, 6A, 6AP, 6B, 6C: Test Switch variations.
- A1, A1E, A3, A4, A62, AB3, AB4: Auxiliary Contacts for various conditions (line failure, emergency, normal, bypass).
- B9: Battery charger connections.
- Calibrate: Allows adjustment of Phase-to-Phase voltage sensing and Frequency.
- CDP: Clock Exerciser (Load/No Load) for simulating power failures and exercising the generator. Configurable for 1, 7, 14, 28, 365 day cycles.
- CDT: One Event Timer Exerciser with adjustable engine exercise timer (5-60 minutes) and configurable run intervals (1, 7, 14, 28 days).
- CTAP: Alarm Panel with Silence button.
- DS: Disconnect Switch (Auto/Inhibit).
- DT, DW: Delayed Transition timers.
- E: Engine Start Contact.
- EL/P: Event Log and System Data recorder.
- F: Fan contact.
- HT: Heater and Thermostat.
- K, K/P: Frequency Meter and Indication.
- L, L1-L4: LCD Indicator for switch position and source availability.
- M1-M86B: Various Amp Meters and Digital Power Meters.
- N1, N2: Running Time Meter and Operation Counter.
- P1, P2: Time Delay for Source 2 Start.
- Q2, Q3, Q7: Remote control inputs for peak shave, inhibit, and inhibit transfer.
- R1-1/R1-3: Source 1 Over Voltage sensing.
- R15/R15D: Load Shed capability.
- R16: Phase Rotation Sensing (prevents transfer between dissimilar phase sequences).
- R26: Interruptable Power Rate Provisions.
- R50: In Phase Monitor (restricts Live-to-Live transfers unless sources are within 7 electrical degrees).
- S5P, S12P, S13P: Auto/Manual selectors and Transfer Commit feature.
- S14, SW1-SW3: Selector switches for test/auto, engine control, and source priority.
- T: Time Delay for Source 1 Stable transfer.
- T3/W3: Elevator Pre-Signal Auxiliary Contacts.
- U: Source 2 Stop Delay Timer (engine cooldown).
- UMD: Universal Motor Load Disconnect Circuit.
- VI: Voltage Imbalance monitoring.
- W: Time Delay for Source 2 Stable transfer.
- YEN: Bypass Timers Key.
- ZNET: Network Communications Interface Card.
How to Set the System Clock
This section provides a step-by-step guide to setting the system clock, time, and date using the SET menu. It requires entering the six-digit access code.
CDT One Event Timer Exerciser
The CDT is a one-event exerciser with an adjustable engine exercise timer (5-60 minutes) and configurable run intervals (1, 7, 14, or 28 days). It can be configured for Load or No-Load operation.
Detailed instructions are provided for configuring (CFG) and setting (SET) the exerciser, initiating a test cycle, bypassing an exercise, and checking the next exercise event. A note indicates that an '*E*' symbol appears on the LCD when an exercise is impending.
CDP Clock Exerciser
The CDP is a Load/No-Load Clock Exerciser that allows the generator to start and run unloaded or simulate a power failure. It can be configured by the end user for 1, 7, 14, 28, or 365 day cycles. It supports multiple independent No Load exercise periods per cycle.
Instructions are provided for configuring (CFG) and setting (SET) the exerciser, bypassing events, and checking the next exercise event. Figure 9 shows the CDP exerciser interface.
Entelli-Switch 250 User Setup - CFG Menu
This menu allows users to turn options ON or OFF via the keypad using a six-digit access code. The page lists numerous configurable options, including timer exercisers, voltage/frequency settings, transfer commit, phase rotation sensing, alarms, and network settings.
Figure 10 shows diagrams of controller inputs/outputs, the lithium battery, and the location of the User Access Code.
Entelli-Switch 250 User Setup - SET Menu
This menu allows users to change adjustable values through the SET menu, requiring the six-digit access code. It lists parameters such as System Clock, Daylight Savings, Exerciser settings (S2 Runtime), Source 1 and Source 2 voltage/frequency (Fail/Restore), Phase Imbalance settings, and various Time Delays (P1, P2, W, T, DT, DW, U).
Figure 10 is referenced again, showing controller interface details.
Entelli-Switch 250 User Setup - System Info
This section explains how to view system data, including Phase-to-Phase Voltages (S1 & S2), Frequency Indication (K/P), Plant Exerciser status, System Information (Serial #, Revision #, Event Log), and Data (Total Life Transfers, Days Powered Up, Total Transfers to S2, Total S1 Failures, Time S1/S2 available). It also covers changing the User Access Code.
Figure 10 is referenced again, showing controller interface details.
Testing
DANGER: HAZARDOUS VOLTAGES CAN CAUSE SEVERE INJURY OR DEATH.
These charts may indicate problems that require authorized ABB Zenith service personnel. Hazardous voltages may exist on termination plugs other than those that go into the Entelli-Switch 250.
Introduction to Testing
A manual operator handle is provided for maintenance. Manual operation must be checked electrically. Both power sources must be disconnected before manual operation. The procedure involves inserting the handle and operating the switch between Source 1 and Source 2 positions, checking for smooth operation. After inspection, cleaning, and servicing, the switch cover is reinstalled, and circuit breakers are reclosed.
An electrical transfer test is initiated by activating the test switch, triggering the P timer, engine start signal, W timer, and transfer to Source 2. Deactivating the test switch initiates retransfer to Source 1 via the T timer, followed by the U timer for engine cooldown.
Test Options
The ATS can be tested in two positions:
- "Auto Position" Full Transfer Test: Checks complete ATS operation by transferring the load from Source 1 to Source 2.
- "Test Position": Recommended for Preventive Maintenance (PM) without interrupting the load via the BYPASS/ISOLATION SWITCH.
NOTE: A periodic test of the transfer switch under load conditions is recommended to insure proper operation. (See National Electric Code articles 700 and 701).
WARNING: When performing a hi-pot or dielectric test on the power section, DISCONNECT the control panel plugs from the microprocessor to avoid potential damage.
ATS Testing
Steps for ATS testing include starting the generator, verifying voltage/frequency/phase sequence, shutting down the gen set, placing it in Auto, and performing a visual inspection. The test is initiated by pressing the TEST button on the LCD keypad, followed by entering the access code. Three test options appear: XFR LOAD (starts generator, transfers load to Source 2), FAST TEST (presets timers to 30 seconds for the test), and NO XFR (starts generator but does not transfer load).
The test option button is pressed and held until the switch transfers or the generator runs for the specified time. Releasing the button before W timer timeout aborts the test (unless "Transfer Commit" is ON). Lamp testing is also available.
Standard Transition
When a test is initiated, the controller starts the Time Delay Source 2 Start Timer (P cycle). Upon completion of the P timer, an Engine start signal is sent to Source 2. When Source 2 voltage and frequency reach "Restore" values, the Time Delay to Source 2 Timer (W) begins. After the W timer, the MX controller initiates a transfer signal to operate the main transfer operator, transferring the load to Source 2. The transfer switch is mechanically locked.
Restoration of Source 1 Power: Deactivating the test switch initiates re-transfer to Source 1. The Time Delay to Source 1 Timer (T) begins its cycle. After the T timer, the MX controller initiates a transfer signal to operate the main transfer operator, transferring the load to Source 1. The transfer switch is mechanically locked.
Immediately after re-transfer, the S2 Stop Delay Timer (U) begins its cycle to allow the Source 2 Engine to run unloaded. Upon completion of the U timer, an Engine stop signal is sent.
Delayed Transition
Source 1 Power Failure: When Source 1 voltage/frequency falls below "Fail" values, the controller initiates the Time Delay Source 2 Start Timer (P cycle). Upon completion of the P timer, an Engine start signal is sent to Source 2. When Source 2 voltage/frequency reach "Restore" values, the Time Delay to open Source 1 timer (W) begins. After the W timer, the MX controller initiates a transfer signal through SCR-NO to operate the main transfer operator, transferring the load to the Open position. The Time Delay to Source 2 timer (DW) begins its cycle. After the DW timer, the MX controller initiates a transfer signal through SCR-E to operate the main transfer operator, transferring the load to Source 2. The transfer switch is mechanically locked.
Restoration of Source 1 Power: When Source 1 power reaches "Restore" values, the controller initiates re-transfer to Source 1. The Time Delay to open Source 2 Timer (T) begins its cycle. After the T timer, the MX controller initiates a transfer signal through SCR-EO to operate the main transfer operator, transferring the load to the Open position. The Time Delay to Source 1 timer (DT) begins its cycle. After the DT timer, the MX controller initiates a transfer signal through SCR-N to operate the main transfer operator, transferring the load to Source 1. The transfer switch is mechanically locked.
Immediately after re-transfer, the S2 Stop Delay Timer (U) begins its cycle to allow the Source 2 Engine to run unloaded. Upon completion of the U timer, an Engine stop signal is sent.
Closed Transition
ABB Zenith Closed Transition Transfer Switches are designed for Make-Before-Break load transfer between two available sources. Paralleling of sources occurs within a predefined synchronization window (less than 100 milliseconds), after which the initial source is disconnected.
Initiating a Closed Transition: Test initiation starts the Time Delay Source 2 Start Timer (P cycle). Upon P timer completion, an Engine start signal is sent to Source 2. When Source 2 voltage/frequency reach "Restore" values, the Time Delay to open Source 1 timer (W) begins. After the W timer, the ATS closes into Source 2 after ensuring proper phase relationship. The SE limit switch activates, and the controller opens the ATS from Source 1. The SNO limit switch activates, and the ATS is now closed into Source 2 without interrupting the load.
Re-Transfer with Closed Transition: Deactivating the test switch initiates re-transfer. When Source 1 voltage/frequency reach "Restore" values, the Time Delay to open Source 2 timer (T) begins. After the T timer, the ATS closes into Source 1 after ensuring proper phase relationship. The SN limit switch activates, and the controller opens the ATS from Source 2. The SEO limit switch activates, and the ATS is now closed into Source 1 without interrupting the load.
The ATS defaults to open transition on Source 1 failure. Closed transition is not possible with only one source. The optional Transition Mode Selector (TMS) allows selection between Open or Closed Transition when both sources are available.
If the ATS fails to open a source within 100 milliseconds during Closed Transition Mode, an alarm sounds, the source is opened, and other transfer operations are disabled until the problem is corrected and "Fail to Open Lockout Reset" is pressed. A signal (STE) will be provided to Shunt Trip the Generator Circuit Breaker if the Transfer Switch remains closed into both Sources for over 325 milliseconds, feeding the load from Source 1. The maximum parallel time is less than 500 milliseconds. The condition must be corrected and the Shunt Trip reset.
The unit is factory set for transfer within 5 electrical degrees. It requires an Isochronous Governor with an operating frequency of 60 +/- 0.2 Hz and a Shunt Trip Breaker on the Generator set with a response time not exceeding 50 milliseconds.
Sequence of Operation
Standard Transition
Source 1 Power Failure: When Source 1 voltage or frequency falls below "Fail" values, the controller initiates the Time Delay Source 2 Start Timer (P cycle). Upon P timer completion, an Engine start signal is sent to Source 2. When Source 2 voltage/frequency reach "Restore" values, the Time Delay to Source 2 Timer (W) begins its cycle. After the W timer, the MX controller initiates a transfer signal through SCR-E to operate the main transfer operator, transferring the load to Source 2. The transfer switch is mechanically locked.
Restoration of Source 1 Power: When Source 1 power reaches "Restore" values, the controller initiates re-transfer to Source 1. The Time Delay to Source 1 Timer (T) begins its cycle. After the T timer, the MX controller initiates a transfer signal through SCR-N to operate the main transfer operator, transferring the load to Source 1. The transfer switch is mechanically locked.
Immediately after re-transfer, the S2 Stop Delay Timer (U) begins its cycle to allow the Source 2 Engine to run unloaded. Upon completion of the U timer, an Engine stop signal is sent.
Delayed Transition
Source 1 Power Failure: When Source 1 voltage or frequency falls below "Fail" values, the controller initiates the Time Delay Source 2 Start Timer (P cycle). Upon P timer completion, an Engine start signal is sent to Source 2. When Source 2 voltage/frequency reach "Restore" values, the Time Delay to open Source 1 timer (W) begins its cycle. After the W timer, the MX controller initiates a transfer signal through SCR-NO to operate the main transfer operator, transferring the load to the Open position. The Time Delay to Source 2 timer (DW) begins its cycle. After the DW timer, the MX controller initiates a transfer signal through SCR-E to operate the main transfer operator, transferring the load to Source 2. The transfer switch is mechanically locked.
Restoration of Source 1 Power: When Source 1 power reaches "Restore" values, the controller initiates re-transfer to Source 1. The Time Delay to open Source 2 Timer (T) begins its cycle. After the T timer, the MX controller initiates a transfer signal through SCR-EO to operate the main transfer operator, transferring the load to the Open position. The Time Delay to Source 1 timer (DT) begins its cycle. After the DT timer, the MX controller initiates a transfer signal through SCR-N to operate the main transfer operator, transferring the load to Source 1. The transfer switch is mechanically locked.
Immediately after re-transfer, the S2 Stop Delay Timer (U) begins its cycle to allow the Source 2 Engine to run unloaded. Upon completion of the U timer, an Engine stop signal is sent.
Table 3 lists Timer Designations as they appear in the SET menu for Standard Transition and Delay/Open Transition.
Closed Transition
ABB Zenith Closed Transition Transfer Switches are designed for Make-Before-Break load transfer between two available sources. Paralleling of sources occurs within a predefined synchronization window (less than 100 milliseconds), after which the initial source is disconnected.
Initiating a Closed Transition: Test initiation starts the Time Delay Source 2 Start Timer (P cycle). Upon P timer completion, an Engine start signal is sent to Source 2. When Source 2 voltage/frequency reach "Restore" values, the Time Delay to open Source 1 timer (W) begins. After the W timer, the ATS closes into Source 2 after ensuring proper phase relationship. The SE limit switch activates, and the controller opens the ATS from Source 1. The SNO limit switch activates, and the ATS is now closed into Source 2 without interrupting the load.
Re-Transfer with Closed Transition: Deactivating the test switch initiates re-transfer. When Source 1 voltage/frequency reach "Restore" values, the Time Delay to open Source 2 timer (T) begins. After the T timer, the ATS closes into Source 1 after ensuring proper phase relationship. The SN limit switch activates, and the controller opens the ATS from Source 2. The SEO limit switch activates, and the ATS is now closed into Source 1 without interrupting the load.
The ATS defaults to open transition on Source 1 failure. Closed transition is not possible with only one source. The optional Transition Mode Selector (TMS) allows selection between Open or Closed Transition when both sources are available.
If the ATS fails to open a source within 100 milliseconds during Closed Transition Mode, an alarm sounds, the source is opened, and other transfer operations are disabled until the problem is corrected and "Fail to Open Lockout Reset" is pressed. A signal (STE) will be provided to Shunt Trip the Generator Circuit Breaker if the Transfer Switch remains closed into both Sources for over 325 milliseconds, feeding the load from Source 1. The maximum parallel time is less than 500 milliseconds. The condition must be corrected and the Shunt Trip reset.
The unit is factory set for transfer within 5 electrical degrees. It requires an Isochronous Governor with an operating frequency of 60 +/- 0.2 Hz and a Shunt Trip Breaker on the Generator set with a response time not exceeding 50 milliseconds.
Controls Power Supply (CPS)
Standard and Delay Transition: Each MX250 microprocessor-based ATS controller requires a Controls Power Supply (CPS) to apply line voltage to the ATS operator via SCRs. Power is also required for the MX250 printed circuit board, and sensing voltage proportional to line voltage is applied. This is accomplished by the CPS, which isolates the MX250 from line voltage and protects it from harmful line transients.
The document includes a table listing Primary Voltage, CPS Assembly Part No., and CPS Board No. for various voltage ranges. Schematics for Standard Transition CPS and Delayed Transition CPS are also provided, detailing connections and component labels.
Troubleshooting & Diagnostics
This section provides a general troubleshooting guide to recognize and determine basic faults. It uses a chart format listing Symptoms, Annunciations (referring to LEDs on the control panel), Possible Causes, and Corrective Actions for common issues such as the engine not starting or stopping, and the ATS failing to transfer to Source 1 or Source 2.
DANGER: HAZARDOUS VOLTAGES CAN CAUSE SEVERE INJURY OR DEATH.
Maintenance and Testing
CAUTION: Due to hazardous voltage and current, ABB Zenith recommends that an ABB Zenith Certified technician or a qualified electrician must perform the installation and maintenance of the switch.
WARNING: Both power sources must be disconnected before manual operation of the switch.
A preventive maintenance program is essential for ensuring high reliability and long life for the transfer switch. Key aspects include:
Inspection and Cleaning
The switch should be inspected for dust, dirt, or moisture accumulation and cleaned with a dry cloth or soft brush. A blower should not be used as it can lodge debris in components. Contacts should be checked, and any surface deposits removed. Pitted or excessively worn contacts should be replaced. A general inspection of mechanical integrity is also recommended.
Servicing
Worn or inoperative parts must be replaced using ABB Zenith recommended parts. Refer to the Replacement Parts manual for specific information. The operating mechanism is lubricated with Lubriplate 105 at the factory, providing adequate lubrication for the switch's lifetime. ABB Zenith offers complete preventative maintenance services.
CDT Battery Replacement: Lithium batteries typically last up to 10 years, but replacement is recommended every 3-5 years. The battery primarily maintains exerciser memory.
Testing
A manual operator handle is provided for maintenance testing. Electrical transfer tests are initiated via the test switch, simulating power failures and generator starts. The sequence involves timers (P, W) for transfer to Source 2 and (T, U) for retransfer to Source 1 and engine cooldown.
NOTE: A periodic test of the transfer switch under load conditions is recommended to insure proper operation (See National Electric Code articles 700 and 701).
WARNING: When performing a hi-pot or dielectric test on the power section, DISCONNECT the control panel plugs from the microprocessor to avoid potential damage.
