You're right to think about using the soft starter I/Os for this. It's generally cleaner and safer than directly interrupting control wiring. Here's a breakdown of approaches, considerations, and a recommended strategy

Understanding the Concerns
Thermal Cutout Action

When the cutout trips, you want the motor to stop safely and the diaphragm valve to close during the soft stop ramp. Abruptly cutting power could cause pressure surges and damage to the pump or system.

Eaton S811+ Features

You've identified the key challenge – standard "External Trip" or "E-Stop" inputs often trigger immediate stops, bypassing the ramp-down functionality. This is undesirable for your application.

Options and Evaluation1. Directly Interrupting Run/Enable



Pros

Simple wiring.

Cons

Not ideal. Hard stops can damage equipment. Loss of control over ramp-down. The soft starter's monitoring and protection features wouldn't be fully utilized.2.

"External Trip" or "E-Stop" Inputs



Pros

Designed for safety interlocks.

Cons

Bypasses ramp-down, defeating the purpose of the soft stop for your pump.3.

Using a Programmable Input (if available): This is the best approach if the S811+ has a programmable input that can be configured for a specific response. Pros

Allows you to customize the action based on the thermal cutout. You can often program it to trigger a controlled stop.

Cons

Requires understanding of the S811+'s programming interface. Might require a digital input that's not already used.4.

Using a Fault Input



Pros

The soft starter's built-in fault handling.

Cons

You need to determine if the "fault" input will automatically activate the soft-stop ramp to close the valve, and it might not have a configurable timer, so it might not be the best solution.

Recommended Strategy (Assuming Programmable Input or configurable Fault input)

1.

Consult the S811+ Manual (CRITICAL)

Thoroughly review the manual's sections on:

Programmable Inputs (if they exist)

Look for an input that can be configured to trigger a "Controlled Stop," "Ramp to Stop," or similar function.

Fault Inputs

Read about the fault setting, and see if the soft-stop function occurs when it triggers.

Parameter Settings

Identify parameters related to input behavior and fault response. Look for options to define what happens on a specific input change.2.

Wiring

Connect the Normally Closed (NC) contact of the motor's thermal cutout to the designated programmable input (or fault input) on the S811+.3.

Configuration (Programming)



If using a Programmable Input

Configure the input to trigger a "Controlled Stop" or "Ramp to Stop." Set any related parameters, such as the ramp-down time, to match the diaphragm valve closure time. This is likely the most flexible and desirable option.

If using the Fault Input

If the soft starter has a configurable timer for ramp down in a fault situation, you could configure it to trigger the timer and close the valve.4.

Testing

Thoroughly test the setup! Simulate a thermal overload by manually opening the thermal cutout contact. Verify: The motor initiates a soft stop ramp. The diaphragm valve closes as expected during the ramp. The S811+ displays a fault or alarm indication related to the external trip.

Why this is best



Safety

Utilizes the soft starter's safety features.

Controlled Stop

Prevents abrupt stops and potential system damage.

Valve Coordination

Ensures the valve closes properly during the ramp-down.

Diagnostics

The soft starter provides a fault indication for troubleshooting.

Clean Integration

Avoids hacking into existing control wiring.

Important Considerations



Diaphragm Valve Timing

The ramp-down time on the soft starter must be sufficient for the diaphragm valve to fully close. Test and adjust this setting carefully.

Documentation

Document all wiring and configuration changes clearly. This is crucial for future maintenance and troubleshooting.

PLC Integration (if applicable)

If your system uses a PLC, consider communicating the soft starter's fault status to the PLC for more comprehensive monitoring.

Motor Protection Coordination

Ensure that the motor's thermal cutout is properly sized and coordinated with any other overload protection devices in the system. This is crucial for reliable motor protection.

Safety Procedures: Always follow proper electrical safety procedures when working with electrical equipment.By using a programmable input on the soft starter, you can integrate the thermal cutout in a way that provides both safety and optimal system performance. Remember, a thorough review of the S811+ manual is the key to success. Good luck! Flag for review