Carrier Ducted Split with iNELS CU3-10M/Modbus
1. Introduction
This guide describes how to integrate Carrier ducted split systems (e.g., 38KSM + 42KSM indoor/outdoor units, R-410A) into the iNELS CU3-10M/Modbus controller.
The integration is achieved using the Carrier Translator 33CNTRAN485-01-R, which converts Carrier’s proprietary CCN (Carrier Comfort Network) protocol into Modbus RTU (RS-485), enabling full two-way communication with iNELS.
2. Required Components
CU3-10M/Modbus (iNELS Central Unit with Modbus Master support)
Optional - Inspinia unit with Addon A-GRS4
Carrier ducted split unit (38KSM outdoor + 42KSM indoor or any)
Carrier Translator 33CNTRAN485-01-R
RS-485 twisted pair cable (shielded, daisy-chain topology)
Power supply for translator (24 VAC / 24 VDC depending on model)
3. System Architecture
[CU3-10M/Modbus] ← RS-485 / Modbus RTU → [33CNTRAN485-01-R] ← CCN → [Carrier Ducted Split Units]CU3-10M or Inspinia unit operates as Modbus Master
Translator acts as Modbus Slave / CCN Master
Multiple Carrier indoor units can be connected to the translator (check translator capacity in datasheet)
4. Wiring & Connections
RS-485 from CU3-10M to Translator (A/B polarity must match).
Termination resistors (120 Ω) at both ends of RS-485 bus.
Shield grounding at one point only (preferably CU3 side).
Translator DIP switch settings → configure for Modbus RTU mode, slave address, and baud rate (default: 9600bps, 8N1).
5. CU3-10M Configuration
In iDM3 (iNELS Design Manager):
Add a Modbus Bus to the CU3-10M device manager.
Create a new device with the translator’s slave address.
Map registers according to Carrier Translator Modbus table (see below).
Assign iNELS objects (bits/integers) for control and monitoring.
6. Modbus Register Mapping (Example)
Room Temperature (°C)
30001 (0x0000)
INT16
Scaled ×10
Setpoint Temperature (°C)
40001 (0x0000)
INT16
R/W, scaled ×10
Operating Mode (Cool/Heat/Fan)
40002 (0x0001)
INT16
R/W, enum (0=Auto,1=Cool,2=Heat,3=Fan,4=Dry)
Fan Speed
40003 (0x0002)
INT16
R/W, enum (0=Auto,1=Low,2=Med,3=High)
On/Off Command
40004 (0x0003)
Coil
0=Off, 1=On
Alarm Status
30002 (0x0001)
Coil
1=Fault present
(Registers may vary depending on translator firmware – verify with Carrier Translator manual.)
7. Testing & Commissioning
Power on all devices and confirm translator LED indicates CCN ↔ Modbus communication.
In iDM3, monitor Modbus values (room temp, setpoint, on/off).
Test control functions:
Change setpoint from iNELS → confirm update on Carrier unit.
Switch modes/fan speeds → confirm indoor unit responds.
Turn unit On/Off → verify.
Check alarm register for error conditions.
8. Use Cases
Centralized HVAC control from iNELS app or SkyThings.
Energy management → automatic shutdown when guest card removed (GRMS).
Scenes & automation → e.g., “Welcome scene” activates AC at comfort temperature.
Monitoring → room temperature and alarms visible on dashboard.
9. Notes
Translator must be ordered separately (Carrier code: 33CNTRAN485-01-R).
Default Modbus baud rate: 9600 bps (can be changed).
Maximum number of Carrier indoor units per translator: typically 16 (check datasheet).
For Modbus TCP integration, an RS-485 → TCP converter is required.
10. References
Carrier Translator 33CNTRAN485-01-R https://www.carrier.com/commercial/en/us/products/controls/carrier-comfort-network/33cntran485-01-r/
Configuration manual https://www.shareddocs.com/hvac/docs/1000/Public/01/808-356.pdf
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