# Carrier Ducted Split with iNELS CU3-10M/Modbus

### 1. Introduction

<figure><img src="/files/ozllDhTi8nJHoZcbyTGJ" alt=""><figcaption></figcaption></figure>

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)**:

1. Add a **Modbus Bus** to the CU3-10M device manager.
2. Create a new device with the translator’s slave address.
3. Map registers according to Carrier Translator Modbus table (see below).
4. Assign iNELS objects (bits/integers) for control and monitoring.

### 6. Modbus Register Mapping (Example)

| Function                       | Register (Hex) | Data Type | Notes                                        |
| ------------------------------ | -------------- | --------- | -------------------------------------------- |
| 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

1. Power on all devices and confirm translator LED indicates CCN ↔ Modbus communication.
2. In iDM3, monitor Modbus values (room temp, setpoint, on/off).
3. 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.
4. 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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