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Siber DF EVO

Modbus RTU
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Last updated: 03. 2026

Requires external gateway

Siber DFEVORFRS485

Siber DF EVO

The Siber DF EVO is a double-flow heat recovery ventilation unit (HRV/ERV) for residential applications, available in four models: DF EVO 1, 2, 3 and 4. The unit communicates wirelessly with the Siber DFEVORFRS485 RF-RS485 gateway, which converts the RF signal to Modbus RTU over RS-485 for integration with TapHome.

The TapHome template provides ventilation speed control with 7 positions, four temperature sensors (indoor, outdoor, supply, exhaust), airflow measurements, bypass position, defrost status, and filter lifecycle management.

Hardware connection

The Siber DF EVO unit does not have a direct RS-485 connection. Communication requires the DFEVORFRS485 gateway (sold separately), which pairs wirelessly with the ventilation unit and exposes Modbus RTU registers over a wired RS-485 bus.

Gateway setup
  1. Connect the DFEVORFRS485 gateway to the RS-485 bus (A+, B-, GND) and to TapHome Core
  2. Pair the gateway with the DF EVO unit following the Siber pairing procedure — during pairing, register H:41003 reports value 254 (“Binding mode active”)
  3. Once paired, the gateway bridges all sensor data and control commands between the ventilation unit and the Modbus bus

The RF communication between the unit and the gateway has a timeout — if no communication is received for 30 minutes, register H:40101 reports an error. Ensure the gateway is within range of the ventilation unit.

Configuration

Modbus connection parameters
ParameterValue
Baud rate19200
ParityEven
Stop bits1
Data bits8
Slave ID1 (default, configurable)
Error monitoring

The module ReadScript monitors register H:41003 for error codes and reports them in TapHome:

CodeMeaningTapHome severity
1Unspecified faultError
2Emergency stopWarning
3Supply fan 1 errorError
4Sensor X22 errorError
5Sensor X23 errorError
6Sensor X21 errorError
7Sensor X20 errorError
8Fan 2 errorError
254Binding mode activeWarning
255Device identification activeWarning

Device capabilities

Ventilation speed control

Ventilation Speed (H:41000 read / H:41500 write) is a multi-value switch with 7 positions:

  • Off — unit stopped
  • Minimum — absolute minimum (away mode)
  • Speed 1 — low
  • Speed 2 — nominal
  • Speed 3 — high
  • Auto — automatic speed regulation
  • Boost — maximum airflow

The read register uses complex mapping (temporary overrides, away mode) that the template normalizes to the 7-position switch. The write register accepts the position index directly.

Fan speed monitoring

Two sensors report the actual fan speed as a percentage (0–100%):

  • Inlet Fan Speed (H:41002) — supply fan speed
  • Exhaust Fan Speed (H:41001) — exhaust fan speed
Temperature monitoring

Four temperature sensors read LittleEndianFloat values across two holding registers each:

  • Indoor Temperature (H:41005–41006) — indoor air temperature
  • Outdoor Temperature (H:41007–41008) — outdoor air temperature, also used for anti-ice protection
  • Supply Temperature (H:41011–41012) — temperature of fresh air supplied to the home after heat recovery
  • Exhaust Temperature (H:41009–41010) — temperature of stale air exhausted from the home

A value of NaN indicates the sensor is unavailable. Values below -273°C indicate a sensor problem.

Airflow measurement

Two sensors read the volume flow rate in m³/h as LittleEndianFloat values:

  • Inlet Airflow (H:41019–41020) — supply air volume flow
  • Exhaust Airflow (H:41021–41022) — exhaust air volume flow

Airflow sensors may not be available on all internal board models (VMD-02RPS78/66). Special value 0x7FFF indicates “not available”.

Bypass and defrost status
  • Bypass Position (H:41016) — bypass damper position as percentage: 0% = closed, 100% = open. Values above 120% indicate an error. The bypass opens automatically based on indoor/outdoor temperature conditions for free-cooling
  • Defrost (H:41015) — anti-ice protection status. The unit engages progressive defrost at low outdoor temperatures
Filter management

Filter Status (H:41042) displays the remaining filter life as an inverted percentage (100% = new, 0% = needs replacement). The ReadScript also monitors H:41014 and adds a warning when the filter is dirty.

Two service attributes provide additional detail:

  • Days Until Filter Replacement (H:41040) — days remaining before the filter should be cleaned or replaced
  • Filter Replacement Interval (H:41041) — configured interval in days

A Reset Filter Timer service action (writes H:42000) resets the filter counter after cleaning or replacement.

Siber recommends checking filters every 3 months, cleaning every 6 months, and replacing at least once a year.

Additional capabilities

The DF EVO also exposes registers for indoor and outdoor humidity (requires optional DFEVOHR wireless sensor), CO2 level (requires optional DFEVOCO2 sensor), air quality index, preheater and post-heater power levels, and per-speed fan percentage configuration. Temporary speed override timers (up to 18 hours) and frost protection setpoints are also available via Modbus. These can be added in a future template update.

Troubleshooting

No Modbus communication
  1. Verify the DFEVORFRS485 gateway is powered and paired with the ventilation unit
  2. Check the RS-485 wiring between the gateway and TapHome Core (A+, B-, GND)
  3. Confirm TapHome is configured for 19200 baud, even parity, 1 stop bit
  4. Check register H:40101 — value 1 indicates RF communication loss between the gateway and the unit (no communication for 30+ minutes)
Sensor readings show NaN or extreme values
  1. NaN indicates the sensor is unavailable — check the physical sensor connection inside the unit
  2. Values below -273°C indicate a sensor hardware problem
  3. Airflow values of 0x7FFF mean the flow sensor is not available on the installed board model
Filter warning in TapHome
  1. The warning “Filter je spinavy” appears when H:41014 reports the filter is dirty
  2. Clean or replace the filter following the Siber maintenance procedure
  3. After replacing the filter, use the Reset Filter Timer service action in TapHome to clear the warning and reset the counter

Available devices

Siber DF EVO Module

Siber DF EVO

Read (module)
switch(modbusr(H, 41003, Uint16),
1, ADDERROR("Nespecifikovana chyba"),
2, ADDWARNING("Nudzove zastavenie"),
3, ADDERROR("Chyba vstupneho ventilatora 1"),
4, ADDERROR("Chyba senzora X22"),
5, ADDERROR("Chyba senzora X23"),
6, ADDERROR("Chyba senzora X21"),
7, ADDERROR("Chyba senzora X20"),
8, ADDERROR("Chyba ventilatora 2"),
254, ADDWARNING("Parovaci rezim je aktivny"),
255, ADDWARNING("Identifikacia zariadenia je aktivna"),
NaN
)
Bypass Position Analog Input Read-only

Heat exchanger bypass damper position — 0% closed, 100% open

Register: H:41016 UInt16 Unit: % numeric

Bypass Position

Read input level
MODBUSR(H, 41016, Uint16) / 100
Filter Status Analog Input Read-only

Air filter remaining life — 100% new, 0% needs replacement; warns when filter is dirty

Register: H:41042 UInt16 Unit: % numeric
Service Attributes
Days Until Filter Replacement
Filter Replacement Interval
Service Actions
Reset Filter Timer

Filter Status

Read (module)
if modbusr(H, 41014, Bool)
	ADDWARNING("Filter je spinavy");
end
Read input level
linear(MODBUSR(H, 41042, Uint16) / 100, 0, 1, 1, 0)
Service Attributes
Cas do vymeny filtra [dni]
modbusr(H, 41040, Uint16)
Interval na vymenu filtra [dni]
modbusr(H, 41041, Uint16)
Service Actions
Vymena filtra
modbusw(H, 42000, Uint16, 0)
Defrost Reed Contact Read-only

Anti-ice protection status — active when low outdoor temperatures require defrost

Register: H:41015 Bool

Defrost

Read
MODBUSR(H, 41015, Bool)
Indoor Temperature Temperature Sensor Read-only
Register: H:41005 LittleEndianFloat Unit: °C numeric

Indoor Temperature

Read temperature
MODBUSR(H, 41005, LittleEndianFloat)
Inlet Airflow Variable Read-only

Supply air volume flow rate in m³/h

Register: H:41019 LittleEndianFloat Unit: m³/h numeric

Inlet Airflow

Read
MODBUSR(H, 41019, LittleEndianFloat)
Exhaust Airflow Variable Read-only

Exhaust air volume flow rate in m³/h

Register: H:41021 LittleEndianFloat Unit: m³/h numeric

Exhaust Airflow

Read
MODBUSR(H, 41021, LittleEndianFloat)
Ventilation Speed Multi-value Switch

Ventilation speed selector — Off, Minimum, Speed 1–3, Auto, Boost

Register: H:41000 → H:41500 UInt16 multi-value
Values / States: ${level_0Of4} · Minimum · Automatika · Boost

Ventilation Speed

Read switch state
var read := MODBUSR(H, 41000, Uint16);
switch(read,
1, 2,
2, 3,
3, 4,
11, 1,
12, 2,
13, 3,
21, 1,
23, 7,
24, 5,
0)
Write switch state
MODBUSW(H, 41500, Uint16, Mu)
Inlet Fan Speed Variable Read-only

Actual supply fan speed as percentage

Register: H:41002 UInt16 Unit: % numeric

Inlet Fan Speed

Read
MODBUSR(H, 41002, Uint16)/200
Exhaust Fan Speed Variable Read-only

Actual exhaust fan speed as percentage

Register: H:41001 UInt16 Unit: % numeric

Exhaust Fan Speed

Read
MODBUSR(H, 41001, Uint16)/200
Outdoor Temperature Temperature Sensor Read-only
Register: H:41007 LittleEndianFloat Unit: °C numeric

Outdoor Temperature

Read temperature
MODBUSR(H, 41007, LittleEndianFloat)
Supply Temperature Temperature Sensor Read-only

Temperature of fresh air supplied to the home after heat recovery

Register: H:41011 LittleEndianFloat Unit: °C numeric

Supply Temperature

Read temperature
MODBUSR(H, 41011, LittleEndianFloat)
Exhaust Temperature Temperature Sensor Read-only

Temperature of stale air exhausted from the home before heat recovery

Register: H:41009 LittleEndianFloat Unit: °C numeric

Exhaust Temperature

Read temperature
MODBUSR(H, 41009, LittleEndianFloat)
Connection: Modbus RTU • 19200 baud• 8E1 • Slave ID: $[SlaveId]
Possible improvements (24)
  • H:41004 Remaining Override Time — Minutes remaining for temporary speed override; only valid when actual speed = 11/12/13 (timer override modes)
  • H:41013 Preheater Level — 0%=off, 100%=maximum, EFh=not available; preheater power level for anti-ice protection
  • H:41017 Indoor Humidity — Relative humidity %, requires optional wireless humidity sensor (DFEVOHR); EFh=not available
  • H:41018 Outdoor Humidity — Not available on VMD-02RPS78/66 models (value=EFh)
  • H:41023 Air Quality — 0%=poor, 100%=excellent; not available on VMD-02RPS78/66 (value=EFh); requires optional sensor
  • H:41024 Air Quality Basis — Bitmask: bit0=VOC, bit1=CO2, bit2=RH; not available on VMD-02RPS78/66
  • H:41025 CO2 Level — ppm, requires optional CO2 sensor (DFEVOCO2); 7FFFh=not available
  • H:41026 Post Heater Level — 0%=off, 100%=maximum, EFh=not available; post-heater power level
  • H:41027 Speed Capability Bits — Bitmask: preheater/postheater available, night/timer/auto/boost/OFF capable, speed 4–10 capable
  • H:41501 Override Time Speed 1 — Write-only, minutes; triggers temporary override to speed 1 (max 18h = 1080 min)
  • H:41502 Override Time Speed 2 — Write-only, minutes; triggers temporary override to speed 2 (max 18h = 1080 min)
  • H:41503 Override Time Speed 3 — Write-only, minutes; triggers temporary override to speed 3 (max 18h = 1080 min)
  • H:42001 Standby Speed Supply — R/W, 0–40%, supply fan speed in standby mode
  • H:42002 Standby Speed Exhaust — R/W, 0–40%, exhaust fan speed in standby mode
  • H:42003 Low Speed Supply — R/W, 0–80%, supply fan speed at low setting
  • H:42004 Low Speed Exhaust — R/W, 0–80%, exhaust fan speed at low setting
  • H:42005 Medium Speed Supply — R/W, 0–100%, supply fan speed at medium setting
  • H:42006 Medium Speed Exhaust — R/W, 10–100%, exhaust fan speed at medium setting
  • H:42007 High Speed Supply — R/W, 0–100%, supply fan speed at high setting
  • H:42008 High Speed Exhaust — R/W, 10–100%, exhaust fan speed at high setting
  • H:42009 Frost Protection Preheater Setpoint — R/W, FLOAT, -20–50°C; temperature setpoint for frost protection preheater activation
  • H:42011 Preheater Setpoint — R/W, FLOAT, -20–50°C; preheater target temperature setpoint
  • H:42013 Free Ventilation Heating Setpoint — R/W, FLOAT, 0–30°C; bypass heating mode activation temperature
  • H:42015 Free Ventilation Cooling Offset — R/W, FLOAT, 1–10 K; bypass cooling mode temperature offset
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