The ATC-300+ is Eaton's newer version of the ATC-300 automatic transfer switch controller. Both do the same job: monitor two power sources and run the transfer and retransfer sequence. For anyone replacing an ATC-300, the key point is that Eaton factory-programs each ATC-300+ for a specific transfer switch, so the replacement has to be matched to your switch before it ships.
Eaton doesn't publish a feature-by-feature comparison of the two generations. What it does publish is the ATC-300+ instruction booklet, which documents the controller in detail and flags several functions as new. This guide covers what that documentation says, what to confirm before ordering, and where to find the right manual.
What Is the Difference Between the ATC-300 and ATC-300+?
The difference is generational. Eaton describes the ATC-300+ as a newer version of the ATC-300, built for the same role. It's a compact, self-contained, panel-mounted microprocessor controller that monitors Source 1 and Source 2 voltage and frequency and decides when to transfer.
Eaton's ATC-300+ manual calls out several functions as new or added:
- Previous-screen navigation: a Previous button lets technicians step back through screens instead of scrolling all the way around.
- Manual retransfer mode: the controller can be set to wait for an operator's pushbutton before returning to normal power, instead of retransferring automatically.
- Field-settable switch type: beginning with firmware version 4.0, the transfer switch product type can be changed from the front panel. Eaton notes this is meant for installing a new controller into an existing switch.
- Full Form C generator start contact: a normally closed generator start contact was added in October 2019.
Because firmware and hardware revisions continue to change, two ATC-300+ units can differ in detail. That's another reason to match by part number and switch data, not by name alone.
What Does the ATC-300+ Include?
The table below summarizes the ATC-300+ as Eaton documents it. Use it to check that a replacement fits your installation's control power, monitoring, and enclosure.
| Item | ATC-300+ per Eaton |
|---|---|
| Display | Backlit 2-line, 16-character LCD |
| Status LEDs | Unit Status, Source 1 Available, Source 1 Connected, Source 2 Available, Source 2 Connected |
| Front-panel functions | Help/Lamp Test, Previous/Engine Test, Next/Enter, Increase, Decrease, Alarm Reset, Bypass Time Delay |
| System voltages | 120–600 Vac, single-phase or 3-phase, 50 or 60 Hz |
| Control power | 65–145 Vac, 50/60 Hz |
| Source monitoring | Under- and overvoltage, under- and overfrequency, voltage unbalance, phase reversal |
| History | 16 most recent transfers with reason, date, and time; run-time and transfer counters |
| Communications | RS-485 with Modbus |
| Panel space | 6.5 × 8.5 in. |
| Standards | UL Recognized Component; complies with UL 1008 / CSA 22.2-178 |
Source: Eaton ATC-300+ Instruction Booklet IB01602009E, 2020
When Is the ATC-300+ Used as a Replacement?
The ATC-300+ is the transfer switch controller on Eaton's LMR Plus FT-series fire pump controllers, where it signals the transfer switch mechanism to operate. When the transfer switch controller on one of these units fails, the replacement is matched to that specific switch.
Eaton is clear that the ATC-300+ isn't a field-repair item. Its manual says that if a malfunction is traced to the controller, the unit should be returned to Eaton for a replacement. The circuit boards are factory-calibrated and serviced only by factory-trained personnel. In practice, a failed controller is replaced, not repaired.
Eaton states that the ATC-300+ is factory-programmed for a specific automatic transfer switch and shouldn't be interchanged without consulting Eaton. A controller that mounts and powers up isn't necessarily set up for your switch.
What Should You Confirm Before Ordering?
Gather the same information Eaton asks for when it supports a transfer switch. With it in hand, the replacement can be matched to your switch on the first try.
- The transfer switch's General Order number (GO#) and item number from the switch nameplate.
- The transfer switch catalog number.
- The controller's style number from the existing ATC-300 or ATC-300+.
- Firmware version and installed options. On a working ATC-300+, these appear when you press Help/Lamp Test from the home screen. On a dead unit, Eaton points to the label on the back of the controller.
- The fire pump controller model and serial number, such as an FT-series unit, from its nameplate.
- System voltage, phase, and frequency.
Replacement and setup should be done by qualified personnel following Eaton's procedure. That includes confirming every setpoint after the new controller is installed, since the replacement has to match your site's voltage, frequency, and timing settings.
Where Can You Find the Correct ATC-300+ Manual?
Eaton publishes the ATC-300+ Operation and Maintenance Manual (IB01602009E) in its fire pump controller documentation library. It covers the controller's hardware, setpoints, operation, troubleshooting, and replacement.
Earlier fire pump editions were published as IM05805022K. Use the manual that matches your controller's firmware, and keep the FT controller's own instruction manual alongside it for anything specific to the fire pump controller.
ATC-300 vs ATC-300+ FAQs
What is the difference between the ATC-300 and ATC-300+?
Eaton describes the ATC-300+ as a newer version of the ATC-300. Both are panel-mounted, microprocessor-based transfer switch controllers that monitor two sources and control transfer and retransfer. Eaton's ATC-300+ manual flags new functions, including previous-screen navigation, a manual retransfer mode, and a front-panel switch-type setting starting with firmware 4.0.
Can an ATC-300+ replace an ATC-300?
The ATC-300+ is the newer controller for this role, but it isn't a grab-and-install part. Eaton factory-programs each ATC-300+ for a specific transfer switch and says not to interchange controllers without consulting Eaton. Confirm the switch's GO# and catalog number and the existing controller's style number before ordering.
What is the part number for the Eaton ATC-300+?
The ATC-300+ automatic transfer switch controller in our catalog is Eaton part number 6D32360G45. Before ordering, compare it with the style number on your existing controller's label and the data on your transfer switch nameplate. If anything doesn't match, call (786) 336-5783 so the right unit can be confirmed for your switch.
Where can I find the ATC-300+ manual?
Eaton publishes the ATC-300+ Operation and Maintenance Manual as IB01602009E in its fire pump controller documentation. Earlier fire pump editions were published as IM05805022K. The manual covers hardware, setpoints, operation, troubleshooting, and the replacement procedure. Use the edition that matches your controller's firmware.
Order an ATC-300+ Replacement
When you're ready to order, see the Eaton ATC-300+ (6D32360G45) controller. Browse related electric transfer switch components, or compare complete fire pump automatic transfer switches.
To confirm the match for your switch, call (786) 336-5783 with your switch GO#, catalog number, and existing controller style number, or send them through our contact form.