S801+ vs S811+ Eaton Soft Starters

A Soft Starter is a device that provides an alternative startup method to a typical AC motor with fewer power requirements at start-up. It reduces the amount of drawn inrush current and limits the motor starting torque; this helps reduce potentially damaging mechanical and electrical shocks on the motor system. When a soft starter is added to a motor’s circuit, it continuously regulates the motor’s supply voltage during the start-up phase. This means that the motor will gradually adjust to the machine’s load behavior. So, the soft starter provides the motor with a smooth acceleration up to full speed. This improves the operating behavior and lengthens the service life of your motor; it also smooths workflows.

As the name suggests, soft starters are mainly used in the start-up phase of electric motors or other mechanical operating equipment. But they can also be used to stop, accelerate, reverse and protect such equipment. Moreover, they are used to reduce motor heating in case of frequent starts and stops. Soft starters are mainly utilized in electric motors for industrial applications requiring huge amounts of inrush currents due to high inertia loads.

Eaton Corporation provides low voltage Soft Starters that are compact, easy-to-program, multifunctional, and easy-to-install. These soft starters are available with current options ranging from 0.8A(Amperes) all through to 1000A, for controlling the acceleration and deceleration of 3-phase motors. In particular, Eaton’s S811+ and S801+ series provide a line of intelligent soft starter technologies designed and built to be the most compact, and the smallest soft starters available in the market today. This article provides a detailed comparison of S801+ versus S811+ Eaton’s Soft Starters, to guide your decision as you select between the two options.

S801+ Soft Starters Overview

The Eaton S801+ Soft Starters are compact(self-contained), enclosure- or panel-mounted soft-starting devices for motors. They utilize six Silicon Controlled Rectifiers (SCRs) connected in a full-wave bridge. By varying the SCR conduction period, the soft starter is able to control the voltage applied to a three-phase motor. After the motor attains full speed, the internal RUN contactors are closed to bypass the SCRs. Also, the S801+ soft starters include an easy-to-use Control Interface Module (CIM). This module enables users to configure the soft starter and evaluate diagnostics/ fault codes for troubleshooting purposes.

Eaton’s S801+ Soft Starters are designed to provide three-phase induction motors in a delta(3-lead) configuration with a smooth start, both electrically and mechanically. They achieve this by controlling the deceleration and acceleration of the 3-phase motors. The S801+ line of reduced voltage soft starters is available for motors with a current rating of 11A all through to 3-phase motors requiring 1000A of steady-state current.

A key feature of the S801+ soft starters is the unique soft-stopping control which provides a smooth transition for stopping electric motors.  Other notable features available with S801+ soft starters include: (i) Adjustable Torque Control. (ii) Inbuilt Overload Protection. (iii) Adjustable Kick Start Control. (iv) Inbuilt RUN bypass contactor. (v) Programmable Overload Settings, which can be adjusted from 31-100% (3.2:1) of rated current for the motor unit. (vi)Multiple electric trip class settings (30, 20, 10 and 5). (vii) Optional CIM door mount safety kit. 

The inbuilt overload kit (has a current ranging from 11A…1000A) and the RUN bypass contactor make installation and setup of the S801+ soft starters quick and easy. The overload feature also provides additional motor protection functions using sophisticated algorithms that model the actual motor heating. 

Moreover, Eaton’s S801+ Soft Starters are engineered to industry standards to meet all the relevant specifications set forth by CSA 22.2-14-1995, CCC GB14048, IEC 60947-4-2, and UL 508.  They come with the following standards approvals and certifications: EN 60947-4-2, IEC 947 compliant, cULus listed (File No. E202571), CSA certification, CSA elevator (2411 01), and CE marked. 

Note, S801 Soft Starters are available in five frame sizes including: (i) S801+N… (ii) S801+R… (iii)S801+T… (iv) S801+U… (v) S801+V… 

S801+ Applications

Essentially, S801+ Soft Starters are designed to control the acceleration and deceleration of three-phase motors in delta(three-lead) configuration. They can work with all motors in that category from those with small fractional horsepower up to the ones requiring 1000A of steady-state current. They are ideally suited for enclosed, open, and Motor Control Center (MCC) applications.

Moreover, the S801+ are among the smallest and most compact soft starters currently available in the market. With their small size, you can easily replace existing soft starter designs, or across-the-line NEMA starters, wye-delta starters, and IEC starters with an S801+ soft starter. Also, the small size feature allows easy retrofits of existing enclosures or MCCs (NEMA 1, 4, 4X, and 12 applications), thereby saving on the costs of adding new structures or replacing existing ones to house a soft starter.

In addition, the S801+ is designed to meet the requirements of industrial applications which require less than 100% of the rated motors’ starting torque for worst-case starting conditions. Such applications include Machine Tools, Chillers, and Pumps. In these applications, the S801+ is used to reduce wear on gears, belts, chains, clutches, bearings, and shafts. As well as ensure less shock on material handling gear and conveyor lines.

S811+ Soft Starter Overview 

The S811+ Soft Starters provide all the reputable features of the S801+ series with additional new and enhanced functionalities. These additional functionalities include a new Digital Interface Module (DIM), communications, comprehensive protection, and metering features, and improved diagnostics capabilities.

The DIM feature allows users to configure the S811+ soft starter, modify control parameters, set communication variables, enable/disable protection, access the fault queue, evaluate fault codes for troubleshooting purposes, and monitor system parameters such as line currents and voltages. The DIM also allows the user to set system variances from maybe Fault TRIP to FAULT WARNING. It also includes an easy-to-read display and a keypad for scrolling through and editing the system parameters.

The S811+ are designed as a complete package of reduced voltage soft starters which combine six Silicon Controlled Rectifiers (SCRs), an inbuilt overload feature, and an internal bypass contactor. The S811+ uses the SCRs to control the voltage to accelerate (soft start) and decelerate (soft stop) the connected three-phase motor. Once the motor starts, the contactors of the internal RUN bypass close, causing the motor to run directly across the line.

The inbuilt solid-state overload feature provides protection to the connected motor against overload conditions using sophisticated algorithms which model the actual motor heating, resulting in fewer nuisance electrical trips and better motor protection. Overall, these advanced protective and diagnostic features help reduce downtime of any motor system that is equipped with an S811+ soft starter.

Also, the S811+ soft starters support integrated communication capabilities through a communication port. This communications port is usually a screw terminal block that is inherently used for Modbus® RTU communications or for communicating to an EATON Human Machine Interface (HMI). A QCPort is also available for connecting communication adapters of other network protocols like EtherNet/IP or external Modbus TCP communication modules.

The Premium S811+ soft starter includes a unique pump control option that uses a sophisticated Eaton-specific algorithm to provide a smooth transition for starting and stopping a three-phase motor in a pump system. This eliminates the potential “water-hammer” effect which could damage pumps, pipes, and valves. With this pump control option, the S811+ series is the number one soft starter family available for centrifugal pumping applications.

The S811+ Series is available in five frame sizes namely: (i) S811+N… (ii) S811+R… (iii) S811+T… (iv) S811+U… (v) S811+V… In addition, the S811+ soft starters are designed and built to meet industry standards. They also come with comprehensive standard approvals and certifications including: CCC GB140, EN 60947-4-2, CSA elevator duty, CCC, IEC 60947-4-2, C-Tick, RoHS, CE, CSAT, UL 508, and ULT.

Typical Applications of S811+ Soft Starters 

The S811+ soft starters provide a wide range of application options. Essentially, they are designed to ensure smooth starts and safe continuous operation of three-phase motors up to 690V with current ratings ranging from 11A to 1000A, even for applications with high load torques. Moreover, this line includes components for panel mounting, in enclosed control (NEMA Type 1, 3R, 4, 4X, 7/9, and 12) and in Motor Control Centers (MCCs). Among others, S811+ soft starters are used in the following applications: 

  • Three-phase inductive loads. 
  • Soft motor start in conveying and transport systems. 
  • Smooth pump start-up to reduce loading shock and wear of the entire pump system; brought about by the “water hammer” effect. 
  • Noise reduction control in buildings. 
  • Fans and Pumps in HVAC (Heating, Ventilation, and Air Conditioning) applications 
  • Solid-state switching of pumps used in extreme environments of filling stations and chemical plants. 
  • Replacement of Star-Delta Starters (particularly for motors rated above 5.5kW, which require a current reducing start-up method). 
  • Smooth belt start-up in fan applications. 

What differentiates an S811+ from an S801+? 

Eaton’s S801+ and S811+ soft starters differ mainly in the following features:

A) Communication: Eaton’s S811+ series provides an option for external communications, unlike the S801+ series. S811+ soft starters are equipped with Modbus RTU communication capabilities as a standard, and they also have a QCPort which allows connection to a variety of communication networks using external communication modules. The networks supported by the QCPort include; EtherNet/IP, Modbus TCP, DeviceNet, and PROFIBUS.

Also, the S811+ soft starters support the use of C441 series communication modules for easy integration into any Programmable Logic Controller (PLC) or Distributed Control System (DCS). The C441 communication modules are not supported by S801+ soft starters.

B) Pump Algorithm: The S811+ series includes a pump control option, which is a factory-installed control option designed to eliminate or reduce the potential for the “water hammer” effect in a centrifugal pump system. This control option utilizes a sophisticated starting and stopping Eaton-specific pump algorithm that is exclusively developed for pumping control applications.

With this option, S811+ soft starters are able to provide a smooth transition during starting and stopping of motors in a pump system. This eliminates the “water-hammer” effect which could damage pumps, pipes, and valves. The S801+ soft starters do not have the pump control option nor do they use the pumping algorithm.

C) User Interface: The S801+ Soft Starters include a Control Interface Module (CIM). This module enables users to configure the soft starter device and evaluate fault codes for troubleshooting. You can use the CIM feature to configure all models of the S801+ series. Moreover, the S801+ is available with an optional CIM door mount safety kit which provides safety functionalities.

On the other hand, the S811+ soft starters have a Digital Interface Module (DIM). This module includes a Liquid-Crystal Display (LCD) and a keypad for scrolling through the various system menus. With the DIM you can modify control parameters, monitor system parameters, set communication variables, enable or disable protections, and access the system’s fault queue.

Also, you have the option of removing the DIM from the S811+ device and mounting it remotely.
DIM door mount kits are also available, enabling operators to safely commission, configure, monitor, and troubleshoot the S811+ system at the electrical control panel with the enclosure door still closed. This helps to eliminate the possibility of arc flash incidents.

D) Programmable Clamps: The S811+ soft starters support analog/digital inputs and programmable relays, which are not supported by the S801+ series. This is because the S811+ series uses C441 communication modules which are available with standard four inputs and two relay outputs. Also, the S811+ soft starters do allow users to program inputs for the following options: (i) 690V option; (ii) Long ramp option; (iii) Inside the delta option; (iv) FAULT WARNING option instead of FAULT TRIP. These programmable input options are not available with the S801+ soft starters.

E) Terminal Assignment: The terminals of the S811+ soft starters are configurable. Whereas the terminals assignment for the S801+ series is not configurable. Hence, an S811+ soft starter could have a similar input configuration as an S801+, except for terminal 3.

F) DIP Switches: A DIP (Dual In-line Package) switch, is actually a set of manual electrical/electronic switches packaged in a small housing. They are designed to allow users to control current flow around expansion cards, Printed Circuit Board (PCB), or other electronics; thereby providing a range of electrical inputs based on the position of the individual DIP switches. Therefore, changing the position of a DIP switch changes the operating mode of an electronic device.

An S811+ soft starter has two functional DIP switches, while an S801+ has only one functional DIP switch. In the S811+ series, the DIP Switch S1 selects Level (OFF) or Edge (ON) sense detection control on the Run1 input- Terminal 1(default) located on the control block. The DIP Switch S2 in S811+ soft starters configures the remote communication port for QCPort (OFF) or Modbus (ON) when the 24 Vdc control unit is powered on. The DIP Switches 32-1 are used to set a unique Remote Field Bus Address (1-63). In the S801+ series, DIP Switch S1 selects Level (OFF) or Edge (ON) sense detection on the Run1 input -Terminal 1(Default) on the control block. DIP Switch S2 and Switches 32-1 are not functional on the S801+ soft starters.

G) Connection: Typical control wiring schemes for both S801+ and S811+ soft starters include basic Connections for 3-Wire Pushbutton and 2-Wire Pushbutton. But the S811+ also includes a wiring scheme for network control.

Similarities between S801+ and S811+ 

A) SCR Technology: Both S801+ and S811+ soft starters utilize six Silicon Controlled Rectifiers (SCRs) components, which are connected in a full-wave power bridge. So, by varying the SCR conduction period it becomes possible to control the voltage supplied to the motor. This in turn regulates the motor’s output torque. Therefore, SCRs allow the supply voltage to the motor to increase gradually, and the motor can run at full speed at different intervals. After the motor attains full speed, the internal RUN contactors are closed to bypass the SCRs.

B) Integrated Bypass: As previously stated, once the motor has attained full speed, the soft starter shifts control over to either an internal or external bypass contactor. The RUN bypass contactor, therefore, acts as a “cruise control”, as it allows the connected motor to run continuously at full speed after start-up.

S801+ and S811+ soft starters feature an integral RUN bypass contactor, which requires only control and power wiring. This integrated bypass allows motors to run continuously in a closed contactor mode after the start-up phase. Eaton’s S801+/S811+ soft starters with an integral bypass are well-suited for pumps, fans, conveyors and other applications in which the current being drawn doesn’t change when the motor is at full speed.

C) Overload Protection: The S811+ and S801+ have a built-in solid-state overload feature. This means that they have a current control loop (overload relay) that monitors and detects changes in the current being drawn by the connected electric motor. They in turn limit the time the overload current is drawn, thereby protecting the motor from drawing too much current and “burning out” due to overheating. Also, both S801+ and S811+ soft starters have advanced overload feature which uses a sophisticated algorithm to model actual motor heating in real-time. This results in better motor protection and minimal nuisance electrical trips.

D) 24 VDC Control: Control devices for motors are typically large and they operate on the same supply voltage as the motors they control. This often results in large Motor-Control Centers (MCCs), which may not provide maximum reliability. For this reason, both S801+ and S811+ soft starters require 24 Vdc control power. By using 24V DC as a control voltage, the two Eaton’s soft starters do increase the reliability of Motor-Control Centers (MCCs).

This is possible as 24V DC power supplies operate with limiting circuits for protection against short circuits. Therefore, in the event of an electrical short, the power supply will simply shut down. This eliminates the need for electrical fuses, as well as the cost and time needed to replace them. Also, the use of 24Vdc control in S811+ and S801+ soft starters reduce system downtime; because once the electrical short is cleared, the 24 V DC power supply will continue to function normally.


Three-phase motors are currently the optimum drive for manufacturing processes, as well as the simple and economic implementation of system and machine concepts. Nevertheless, a star-delta start or direct-on-line motor start-up is not always the best option. For this reason, S801+ and S811+ soft starters are designed to provide a smooth alternative for almost every application for protected power networks and judder-free motor starts and stops. In particular, Eaton’s S811+ and S801+ series deliver an improved motor performance that transcends the standard protection and diagnostic features found in most motor starters.

And from the detailed comparison provided in this article, it is conclusive that S811+ Soft Starters provide all the popular features of the S801+ series with additional new and enhanced functionalities. The additional functionalities include a new Digital Interface Module (DIM), flexible communications, comprehensive protection, and metering features, and improved diagnostics capabilities. Hence, choosing either an S801+ or an S811+ soft starter will increase the productivity of your motor system, reduce downtimes and repair costs. But for advanced motor protection and communications flexibility, the S811+ Series would be the best choice.

We hope that this review of Eaton’s S801+ and S811+ Drive models has been helpful in understanding and evaluating your Eaton drive replacement or repair needs.  For more information or to discuss which PLC Control and Instrumentation solution might be best for your application, please visit our website here, or contact us at sales@dosupply.com or 1-800-730-0292. 

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