Samsung HVAC ⇌ MQTT

Control of select Samsung residential HVAC units over MQTT by emulating a secondary wired remote control.

Planned features:

• Emulate a secondary wired remote control for correct integration onto the WRC bus.
• Report status to MQTT topics.
• Allow changing of parameters via MQTT topics.

Status

• [x] Frame Decoding
• [ ] Tracking, bus enumeration and feature detection
  • i.e, how the sub WRC knows which indoor units to talk to, and what features they have.
• [ ] Command Decoding (partially complete)
• [ ] Sub WRC emulation (in-progress)
• [ ] MQTT integration

This project also contains partial emulators for the Main WRC, Indoor Units, and ERVs to aid in reverse-engineering the WRC protocol.

Compatibility and Limitations

My HVAC system is single zone, single unit, single remote. I'm unable to test the more advanced features supported on more complex systems such as multiple zones, multiple indoor units, ERV/ventilators, blade control, humidity/CO² reading, etc, though I have had some success reverse engineering the protocol to implement partial support for these features.

Notably Command 0xA0 ("Change Indoor Unit Settings") still has a number of unknowns fields. As this is a blanket "change all" settings command I cannot predict how this functions on systems that support additional untested features.

The COM2/WRC bus possibly has two protocol versions: non-NASA and NASA. This project currently only supports the non-NASA variant. If your controller model number ends with N the bus is using the NASA variant.

My system topology is:

My assumption is that the following wired remote controls talk the same protocol:

Background

Samsung HVAC units have two RS-485 control buses: COM1 (F1/F2) and COM2 (F3/F4). The first (COM1) connects the indoor units (such as ceiling cassettes, in-roof duct units, and wall-mount consoles) to their counterpart outdoor units. The second (COM2) connects the indoor units to the wired remote controls (WRC).

This project currently focuses on the second (COM2) bus (which this project terms the WRC bus).

Glossary

Some useful terminology definitions:

ERV: Energy Recovery Ventilator

FJM: Free Joint Multi

EMS: ECO Heating System

DVM: Digital Variable Multi

VRF: Variable Refrigerant Flow

MDS: Motion Detect Sensor

EEV: Electronic Expansion Valve

RMC address: indoor unit group address

SAC: System Air-conditioner Control

NASA: ?

• seems to be for newer/higher power/commercial units
• completely different protocol (apparently)
• The wired remotes come in NASA (e.g. MWR-WE10N) and non-NASA variants (MWR-WE10).
• RAC (Non-Nasa Protocol), CAC (Nasa Protocol),
• Software: SAMSUNG SNET PRO (Old protocol), SNET PRO 2 (NASA Protocol)

RAC: Residential AC

CAC: Commercial AC

AHU: Air Handling Unit

Thanks

Many thanks to Danny De Gaspari for his excellent work on Samsung-HVAC-buscontrol. Without his initial reverse enginering work this project wouldn't be possible.