Power Transfer Switches

ASCO SERIES 300 Group G Power Transfer Switch

Automatically transfer critical loads in the event of a power outage with the ASCO SERIES 300. Rugged construction and proven performance assure the user of many years of reliability.​​

Best Suited For
  • Banking, Financial and Insurance
  • Broadcast and Entertainment
  • Construction and Engineering
  • Data Center/Colocation/Hosting
  • Education
  • Fire/Alarm/Security
  • Government
  • Healthcare
  • Manufacturing
  • Power Generation
  • Power/Gas Transmission and Distribution
  • Retail and Wholesale
  • Telecom
  • Transportation
Packaged Power Warranty


*To see model-specific downloads, you will need to go to the model-specific product page by selecting the model name in the specifications chart above.


The SERIES 300 is listed to UL 1008 standard for total system loads
and CSA standard C22.2 for automatic transfer switches.
Meets NFPA 110 for Emergency and Standby Power Systems.
Easy-to-navigate 128x64 graphical LCD display with keypad provides LED indicators for switch position, source availability, not in auto mode, and alert condition.​


No danger of the SERIES 300 ATS transferring loads to a dead source because the unique ASCO single-solenoid operator derives power to operate from the source to which the load is being transferred.
Integrated multilingual user interface for configuration and monitoring.
Adjustable time-delay feature prevents switch from being activated due to momentary utility power outages and generator dips

Services & Support


Frequently Asked Questions
How does an ATS function?
The ATS works like a conventional open transition transfer switch. The transfer switch main contacts moves in a quick break - before make mode transition. There is no momentary parallel connection of the two sources and no extended center-off position during transfer. The transition is quick. The ATS controller monitors the voltage and frequency of the two sources (upon re-transfer or any transfer between 2 “live” sources) and ensures that they are in-phase before the load is transferred (if enabled).
Is my generator compatible with an ASCO transfer switch, and where do I land my engine start connections?
ASCO Series 3ATS and 3NTS transfer switches can accommodate any generator brand as long as it is has a 2 wire input engine start signal for automatic engine control. These input wires are connected to the engine start contacts of the transfer switch; which will turn the generator ON and OFF when the contacts are closed and opened respectively. Refer to the transfer switch wiring diagram for the terminal connections.
How do I contact a service technician?
Contact a local ASCO Services representative by calling the toll free hotline (1-800-800-2726), then go to option 2 then 3 on the prompt or connect with any customer service representative. They will transfer you to a local service technician’s office in your area.
How do I communicate with the ATS?
Communication through the Group G controller is achieved through 3 types of protocols, ASCOBusI, ASCOBusII and Modbus. ASCOBusI and ASCOBusII are proprietary protocols used to communicate amongst ASCO devices. Third party systems can communicate with the Group G controller using Modbus protocol in conjunction with the 72EE Ethernet connectivity module as an added accessory. The 72EE module also supports SNMP traps and has an onboard webpage. Communication is also available via two and four wire serial connections using the RS-485 port which is part of the 11BE accessory bundles.
What is included in the 11BE accessory bundle and how do I configure them?
If optional Accessory 11BE bundle is ordered, the controller is factory configured with four additional functions: communication, programmable exerciser, event log, common alarm output contact option OP1 (in the controller). Communication can be configured under General settings. Advanced Programmable Engine Exerciser can be configured under Engine Exerciser settings. Events can be viewed under the Event Log main menu. Common Alarms can be configured under General settings.


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Justin Mitros
Email Contact +1 571 313 8041 Fax +1 703 342 0391
12310 Pinecrest Road, Suite 204 Reston Virginia 20191 USA
Product areas of focus: Transfer Switches, Paralleling Switch Gear, Power Control and Monitoring
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6255 Halle Drive Cleveland Ohio 44125 USA
Product areas of focus: Load Banks
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12310 Pinecrest Road Reston Virginia 20191 USA
Product areas of focus: Surge Protective Devices
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