---
source_pdf: "modbus_templates/Helios/easyControls 3.0 - Modbus_RTU_25483-001_V01_0521.pdf"
pages_extracted: "1-20"
snapshot_date: 2026-03-20
relevance: high
notes: "Official Helios easyControls 3.0 Modbus RTU functional and interface description. Document 25483-001 V01/0521. Contains complete register map with all holding register addresses. Trilingual: DE/EN/FR. This is the PRIMARY source for TapHome integration."
---

# Helios easyControls 3.0 — Modbus RTU Functional and Interface Description

**Document:** 25 483-001/-/V01/0521
**Publisher:** HELIOS Ventilatoren GmbH + Co KG, Lupfenstrasse 8, 78056 VS-Schwenningen, Germany
**Website:** www.heliosventilatoren.de
**Applies to:** Helios KWL ventilation units with easyControls 3.0
**Protocol:** Modbus RTU
**Pages:** 20 (DE section pp.1-5, EN section pp.1-5, FR section pp.1-5, plus cover/back pages)

---

## Chapter 1 — General Information

### 1.1 Important Information

To ensure safety and correct operation, read and observe all instructions carefully before proceeding. This document is part of the product and should be kept accessible. Following commissioning, the document must be handed out to the operator.

**WARNING:** The electrical connection must be fully isolated from the power supply up to the final assembly!

### 1.2 Warning Instructions

Warning symbols used in this document:
- **DANGER** — Indicates dangers which will directly result in death or serious injury if the safety instruction is not followed.
- **WARNING** — Indicates dangers which will result in death or serious injury if the safety instruction is not followed.
- **CAUTION** — Indicates dangers which can result in injuries if the safety instruction is not followed.
- **ATTENTION** — Indicates dangers which can result in material damage if the safety instruction is not followed.

### 1.3 Safety Instructions

Special regulations apply for use, connection, operation, transportation and maintenance. Consultation is required in case of doubt. Further information can be found in the relevant standards and legal texts.

---

## Chapter 2 — Variables

### 2.1 Modbus Parameters

#### 2.1.1 Profile Priority

If more than one profile is active simultaneously, then the profile with higher priority will override the profile with lower priority.

**Example:** The fireplace function and boost ventilation profiles are both active at the same time => the fireplace function will override the boost ventilation due to its higher priority.

#### 2.1.2 Priority Order

1. Profile timer configurable input (assigned to digital inputs)
2. Profile fireplace function
3. Profile boost ventilation
4. Profile at home/away

#### 2.1.3 Supported Function Codes in the Modbus RTU

Modbus (RTU) Holding Registers are 16 bits long (unsigned word).

- **FC 03h: FCODE_READ_HOLDING_REGISTERS** — Reading setup values and configuration parameters
- **FC 10h: FCODE_WRITE_HOLDING_REGISTERS** — Writing setup values and configuration parameters
- **FC 06h: FCODE_WRITE_SINGLE_REGISTER** — Writing single setup values and configuration parameters

#### 2.1.4 Modbus Default Setting of the Unit

The Modbus default values can be changed via KWL-BE Touch or on the internal web server.

| Parameter | Default Value |
|-----------|--------------|
| Address | 1 |
| Baud rate | 19200 |
| Parity | even |
| Stop bit | 1 |

---

### 2.1.5 Unit Addresses — Complete Register Map

**External Modbus (Master): 19200-8-E-1, Ventilation unit (Slave): 1**

All registers are Holding Registers (FC03/FC06/FC10). Values are 16-bit unsigned words (Uint16).

**NOTE:** cK = CentiKelvin. 1 degree Celsius = 27315 CentiKelvin = 273.15 Kelvin (note: in range column, 1 degree Celsius = 27415 CentiKelvin per FR section clarification).

#### Sensor Readings (Read-Only)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 4353 | FAN_SPEED | R | 0 | 100 | % | Current fan speed |
| 4354 | TEMP_EXTRACT_AIR | R | 21000 | 33224 | cK | Temperature, extract, cell input |
| 4355 | TEMP_EXHAUST_AIR | R | 21000 | 33224 | cK | Temperature, extract, cell output |
| 4356 | TEMP_OUTDOOR_AIR | R | 21000 | 33224 | cK | Temperature, supply, cell input |
| 4358 | TEMP_SUPPLY_AIR | R | 21000 | 33224 | cK | Temperature, supply, heater output |
| 4363 | RH_VALUE | R | 0 | 100 | RH% | RH value, highest measurement read, 0 = No sensor |
| 4364 | CO2_VALUE | R | 0 | 10000 | PPM | CO2 value, highest measurement read, 0 = No sensor |
| 4369 | MULTISENSOR_TEMP | R | 0 | 65535 | 12BIT | Temperature from internal sensor |
| 4370 | MULTISENSOR_RH | R | 0 | 65535 | 12BIT | Humidity from internal sensor |

#### External Sensor Readings (Read-Only)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 4373 | RH_SENSOR_0 | R | 0 | 65535 | RH% | RH value from sensor 0, 65535 = No sensor |
| 4374 | RH_SENSOR_1 | R | 0 | 65535 | RH% | RH value from sensor 1, 65535 = No sensor |
| 4375 | RH_SENSOR_2 | R | 0 | 65535 | RH% | RH value from sensor 2, 65535 = No sensor |
| 4376 | RH_SENSOR_3 | R | 0 | 65535 | RH% | RH value from sensor 3, 65535 = No sensor |
| 4377 | RH_SENSOR_4 | R | 0 | 65535 | RH% | RH value from sensor 4, 65535 = No sensor |
| 4378 | RH_SENSOR_5 | R | 0 | 65535 | RH% | RH value from sensor 5, 65535 = No sensor |
| 4379 | CO2_SENSOR_0 | R | 0 | 65535 | PPM | CO2 value from sensor 0, 65535 = No sensor |
| 4380 | CO2_SENSOR_1 | R | 0 | 65535 | PPM | CO2 value from sensor 1, 65535 = No sensor |
| 4381 | CO2_SENSOR_2 | R | 0 | 65535 | PPM | CO2 value from sensor 2, 65535 = No sensor |
| 4382 | CO2_SENSOR_3 | R | 0 | 65535 | PPM | CO2 value from sensor 3, 65535 = No sensor |
| 4383 | CO2_SENSOR_4 | R | 0 | 65535 | PPM | CO2 value from sensor 4, 65535 = No sensor |
| 4384 | CO2_SENSOR_5 | R | 0 | 65535 | PPM | CO2 value from sensor 5, 65535 = No sensor |

#### Temperature & Optional Sensors (Read-Only)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 4389 | TEMP_OPTIONAL | R | 20000 | 33224 | cK | Optional external temperature sensor |

#### State & Control Registers (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 4609 | STATE | R/W | 0 | 1 | — | General state [0 = Home, 1 = Away] |
| 4612 | BOOST_TIMER | R/W | 0 | 65535 | MIN | Remaining time Timer boost ventilation (note data point 21766, 65535 = Duration active) |
| 4613 | FIREPLACE_TIMER | R/W | 0 | 65535 | MIN | Remaining time Timer fireplace mode (note data point 21767, 65535 = Duration active) |
| 4615 | WEEKLY_TIMER_ENABLED | R/W | 0 | 1 | — | Weekly timer state [0 = off, 1 = on] |
| 4616 | CELL_STATE | R | 0 | 3 | — | Cell state [0 = heat recovery, 1 = cool recovery, 2 = bypass, 3 = defrosting] |

#### Date/Time Registers (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 4849 | MINUTE | R/W | 0 | 59 | MINUTES | Minutes of the current time |
| 4850 | HOUR | R/W | 0 | 23 | HOURS | Hours of the current time |
| 4851 | DAY | R/W | 1 | 31 | DAYS | Days of the current date |
| 4852 | MONTH | R/W | 1 | 12 | MONTHS | Months of the current date |
| 4853 | YEAR | R/W | 0 | 99 | YEARS | Years of the current date |
| 4854 | WEEKDAY | R | 1 | 7 | WEEKDAY | Weekday [1 = Mon, 2 = Tue, 3 = Wed, 4 = Thu, 5 = Fri, 6 = Sat, 7 = Sun] |

#### Network & Addressing (Read-Only)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 8194 | GW_ADDRESS_1 | R | 0 | 65535 | — | Gateway address (0xAABB) |
| 8195 | GW_ADDRESS_2 | R | 0 | 65535 | — | Gateway address (0xCCDD) |
| 8196 | MASK_ADDRESS_1 | R | 0 | 65535 | — | Mask (0xAABB) |
| 8197 | MASK_ADDRESS_2 | R | 0 | 65535 | — | Mask (0xCCDD) |
| 8212 | IP_ADDRESS_1 | R | 0 | 65535 | — | IP address first two bytes (0xAABB) |
| 8213 | IP_ADDRESS_2 | R | 0 | 65535 | — | IP address last two bytes (0xCCDD) |

#### Fireplace Mode Settings (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 20487 | FIREPLACE_EXTR_FAN | R/W | 0 | 100 | % | Extract fan speed at fire place mode |
| 20488 | FIREPLACE_SUPP_FAN | R/W | 0 | 100 | % | Supply fan speed at fire place mode |

#### Threshold & Limit Settings (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 20490 | RH_BASIC_LEVEL | R/W | 0 | 65535 | % | RH basic level, 65535 = not calculated |
| 20491 | CO2_THRESHOLD | R/W | 500 | 2000 | PPM | CO2 threshold |

#### Profile: Away Settings (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 20499 | AWAY_RH_CTRL_ENABLED | R/W | 0 | 1 | — | RH control in use, away [False, True] |
| 20500 | AWAY_CO2_CTRL_ENABLED | R/W | 0 | 1 | — | CO2 control in use, away [False, True] |
| 20501 | AWAY_SPEED_SETTING | R/W | 0 | 100 | % | Fan speed at away state |
| 20502 | AWAY_AIR_TEMP_TARGET | R/W | 27815 | 29815 | cK | Supply air target temp at away state |

#### Profile: Home Settings (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 20505 | HOME_RH_CTRL_ENABLED | R/W | 0 | 1 | — | RH control in use, home [False, True] |
| 20506 | HOME_CO2_CTRL_ENABLED | R/W | 0 | 1 | — | CO2 control in use, home [False, True] |
| 20507 | HOME_SPEED_SETTING | R/W | 0 | 100 | % | Fan speed at home state |
| 20508 | HOME_AIR_TEMP_TARGET | R/W | 27815 | 29815 | cK | Supply air target temp at home state |

#### Profile: Boost Settings (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 20511 | BOOST_RH_CTRL_ENABLED | R/W | 0 | 1 | — | RH control in use, boost [False, True] |
| 20512 | BOOST_CO2_CTRL_ENABLED | R/W | 0 | 1 | — | CO2 control in use, boost [False, True] |
| 20513 | BOOST_SPEED_SETTING | R/W | 0 | 100 | % | Fan speed at boost state |
| 20514 | BOOST_AIR_TEMP_TARGET | R/W | 27815 | 29815 | cK | Supply air target temp at boost state |

#### Filter & Maintenance (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 20537 | FILTER_CHANGE_INTERVAL | R | 30 | 365 | days | Interval for filter change indicator (reload value) |
| 20543 | RH_LEVEL_MODE | R/W | 0 | 1 | — | RH control mode [0 = Automatic level update, 1 = Manual] |
| 20544 | BOOST_TIME | R/W | 1 | 65535 | min | Boost timer load value |
| 20545 | FIREPLACE_TIME | R/W | 1 | 65535 | min | Fireplace timer load value |
| 20546 | FILTER_CHANGED_DAY | R/W | 1 | 31 | days | Last filter change date (day) |
| 20547 | FILTER_CHANGED_MONTH | R/W | 1 | 12 | months | Last filter change date (month) |
| 20548 | FILTER_CHANGED_YEAR | R/W | 0 | 99 | years | Last filter change date (year) |

#### Timer Enable Registers (Read/Write)

| Address | Variable Name | R/RW | Min | Max | Type | Description |
|---------|--------------|------|-----|-----|------|-------------|
| 21766 | BOOST_TIMER_ENABLED | R/W | 0 | 1 | — | Boost timer enabled [off, on] |
| 21767 | FIREPLACE_TIMER_ENABLED | R/W | 0 | 1 | — | Fire place timer enabled [off, on] |
| 21772 | EXTRA_TIMER_ENABLED | R/W | 0 | 1 | — | Timer configurable input activated [off, on] |

---

## 2.2 Connection

### Wiring Diagram

The connection diagram shows a Modbus RTU bus topology with:
- **MODBUS Master** at the top
- **MODBUS Slave 1, 2, ... n** daisy-chained below
- Each unit connects via its terminal block (MB_A, MB_B for RS-485 data lines)
- **Termination resistor R = 120 Ohm** required on the last device in the chain
- RS-485 connections: MB_A (Data+), MB_B (Data-)
- Additional terminals visible: NTC, GND, +24V, RS_A, RS_B, +11V, AW1, SW1, +24V, GKZ, RMC

---

## Chapter 3 — Other/Notes

All external names, trademarks, WWW links used are the property of the respective companies and are in no way connected to Helios Ventilatoren GmbH + Co KG, hereinafter Helios.

Helios accepts no liability for textual errors, figures and the information is non-binding. The right is reserved to make technical changes without notification.

**ATTENTION: Use of the protocol Modbus is at the user's own risk.**