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Asco 300 Auto Transfer Switch (1Ph, 70A)


SKU: D03ATSA20070FG Category Tag Brand:
Availability: Please call for current lead time
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Free Shipping in the Continental United States
Please call for orders to Alaska or Hawaii.

This Asco Series 300 Automatic Transfer Switch is designed for Single Phase applications up to 70 Amps.

The ASCO Series 300 transfer switch automatically transfers critical loads in the event of a power outage. Rugged construction and proven performance assure the user of many years of reliability. Designed for telecom, commercial, municipal, industrial, and agricultural applications. Also designed to handle the extraordinary demands placed on the switch when starting or restarting installed motors and switching high inrush loads.


  • The Series 300 is listed to UL 1008 standard for Transfer Switch Equipment and CSA standard C22.2 for automatic transfer switches.
  • Meets NFPA 110 for Emergency and Standby Power Systems and the National Electrical Code (NEC) Articles 700, 701 and 702.
  • True double-throw operation: The single solenoid design is inherently inter locked and prevents contacts from stopping between sources or from being in contact with both sources at the same time.
  • There’s 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.
  • Operating parameters and feature settings can be adjusted without opening enclosure door.
  • Supplied with solid neutral termination. (Optional switched neutral pole available.)
  • Compact design for optimum utilization of space.
  • Designed to be completely front- accessible, permitting the enclosures to be installed flush to the wall and still allows installation of all power cabling and connections from the front of the switch.  
  • Numerous enclosure options including UL Type 1 (indoor) and UL Type 3R (outdoor).
  • Accessory 44A Strip Heater is now included for all models with a 3R outdoor enclosure. Prevents condensation and freezing that can shorten the life of the ATS. External 120 volt power source required. Thermostat included.
  • Accessory 11BE Feature Bundle is now included with all new Asco 300 ATS. This accessory offers a programmable engine exerciser, event log, enabled RS-485 communication port, and common alarm output contact.


Asco Series 300 New Microprocessor Controller (Group G)

  • groupg-lcd-sm.jpgEasy to navigate 128×64 graphical LCD display with keypad provides LED indicators for switch position, source availability, not in auto, and alert condition. It also includes test and time delay bypass soft keys.
  • 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.
  • Adjustable time-delays for engine start, engine cooldown, transfer, and re-transfer.
  • Inphase monitor to transfer motor loads, without any intentional off time, to prevent inrush currents from exceeding normal starting levels.
  • Voltage and frequency sensing.
  • Engine exerciser to automatically test backup generator each week with or without load (order Accessory 11BE or 72EE for more engine exerciser options).
  • Statistical ATS system monitoring information.
  • Diagnostic functions.
  • Password protection to prevent unauthorized tampering of settings.
  • Further details can be found in the brochure and controller guide below. See pictures above for informative visuals.


Asco 300 Brochure

Asco 300 Microprocessor Controller

Asco 300 Warranty


Please Call to Order Transfer Switches With These Options:

  • Switched neutral pole (solid neutral is standard).
  • Other 60Hz voltages – up to 600 VAC.
  • 50Hz frequency/voltages.
  • Other enclosures: Open Style, UL Type 4, 4X, or 12.
  • Extended warranties: 3, 4, or 5 years.

Please Note: Some Specs (including withstand ratings, dimensions, and weights) may vary with some of the options above. Please see the Asco 300 Brochure above for details.


Please see below for more information and to order. Accessories ordered with your transfer switch will be factory-installed (as applicable).

  • acc-1up-sm.jpgAccessory 1UP UPS Back Up Power – Allows controller to run up to 3 minutes without AC power. (Also available as a customer-installed Field Kit.)
  • acc-18rx-sm.jpgAccessory 18RX Relay Expansion Module (REX) – Provides for some commonly used accessory relays, includes one form C contact for source availability of normal (18G), and one contact for availability of emergency (18B). Contact rating is 5 amps @ 30VDC or @ 125 VAC resistive). Additional output relay is provided, the default is to indicate a common alarm. See operator’s manual for configurable options. (Also available as a customer-installed Field Kit.)
  • Accessory 135L Power Meter 5210 – For enhanced monitoring of power and energy information on the load side. Includes shorting block and CT’s. (Also available as a customer-installed Field Kit. Not compatible with Accessory 23GA/23GB.)
  • acc-23g-sm.jpgAccessory 23GA/23GB Load Current Metering Card – Measures either single phase (23GA) or three phase (23GB) load current. Includes CT’s. (Not compatible with Accessory 135L.)
  • Accessory 30A Load Shedding Circuit – Initiated by opening of a customer–supplied contact. For ATS only. (Not available as a Field Kit.)
  • Accessory 30B Load Shedding Circuit – Initiated by removal of customer–supplied voltage. Please specify voltage. For ATS only. (Not available as a Field Kit.)
  • Accessory 62W Audible Alarm – Signals each time the switch transfers to emergency. Includes a silencing feature. City of Chicago requirement. (Not available as a Field Kit.)
  • acc-72ee-sm.jpgAccessory 72EE Quad Ethernet Module – Enables remote monitoring and control capabilities. Includes Accessory 11BE Feature Bundle. (Also available as a customer-installed Field Kit.)
  • Single Channel 5310 Annunciator – Provides remote monitoring and control of one Asco 300 transfer switch. Requires Accessory 72EE. (Not factory-installed.)
  • Eight Channel 5350 Annunciator – Provides remote monitoring and control of one Asco 300 transfer switch. Requires Accessory 72EE. (Not factory-installed.)
Model Number






Withstand Rating @ 240V


Frame / Cabinet Type

Service Entrance Rated

Full Dimensions HxWxD (inches)

Weight (NEMA 1)

Weight (NEMA 3R)



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