What is RS485 Communications?
RS485 is a digital communications interface that allows an ATC chiller to exchange information with compatible external control or monitoring equipment.
It can be used to integrate the chiller into a wider system, allowing information from the chiller controller to be accessed remotely rather than relying solely on the controls at the unit itself.
RS485 communications are standard on many current ATC chillers.
What can RS485 be used for on an ATC chiller?
RS485 allows compatible external equipment to read and write controller registers on the chiller.
This supports remote monitoring and integration with equipment such as:
- PLCs
- Machine control systems
- Test equipment
- Process monitoring systems
- Other compatible automation and control equipment
One of the key benefits is the ability to remotely adjust the chiller’s temperature setpoint from a compatible external control system.
This can be particularly useful where the chiller forms part of a larger machine or automated process.
Why is RS485 useful?
In many industrial, laboratory, and OEM applications, the chiller is only one part of a wider system.
RS485 enables information to be exchanged digitally between the chiller and that system, supporting more integrated process monitoring and control.
For example, it can allow an operator or control system to access chiller information without needing to interact directly with the controller on the front of the unit.
This can be particularly useful for automated processes, test systems, and installations where multiple pieces of equipment need to operate as part of a coordinated system.
Can I change the temperature setpoint using RS485?
Remote setpoint adjustment is one of the main benefits of RS485 communications on compatible ATC chillers.
An appropriately configured external system can write to the relevant controller register to change the required temperature setpoint.
This can be useful where different process stages require different temperatures or where temperature control needs to be managed from a central system.
Always refer to the communications information for your specific chiller before configuring an external control system.
Can RS485 remotely start or stop the chiller?
RS485 communications do not provide remote stop/start functionality on ATC chillers.
If your application requires the chiller to be remotely started or stopped by another machine or control system, this should be specified separately.
ATC offers a Remote Stop/Start Option Pack (OP00005) on compatible models. This uses a customer-provided +24V signal through the appropriate connection.
If remote stop/start is important to your application, let ATC know when specifying a chiller.
Is RS485 the same as a Volt Free Contact?
RS485 and Volt Free Contacts provide different types of communication.
RS485 provides digital communication with the chiller controller, allowing compatible external equipment to read and write controller information.
A Volt Free Contact provides a simpler isolated contact that changes state when the chiller enters an alarm condition. The customer’s control system can monitor this contact to recognise the alarm.
How do I connect to the RS485 on my ATC chiller?
On current ATC models, RS485 and Volt Free Contacts are provided through a 9-pin D-sub connection.
The exact connection and communications requirements should be taken from the documentation for your specific chiller.
Before connecting a PLC, machine controller, or other external system, refer to the relevant product and communications information for details of the connection and available controller registers.
Do I need RS485 for my application?
Not every application needs external communications.
If the chiller will operate independently and the temperature setpoint will normally be controlled directly from the unit, the standard local controls may be sufficient.
RS485 becomes particularly useful where the chiller needs to be monitored or controlled as part of a wider automated system.
If you’re specifying a chiller for integration into OEM equipment, a test system, production machinery, or another automated process, discuss the communications requirements with ATC at the quotation stage.
