Daikin Altherma 3 H HT ETVH16S18E6V7

Air-to-water heat pump

Daikin's combination table pairs the ETVH16S18E6V7 indoor unit with EPRA14DV37 and lists DCOM-LT/MB as an option. The accessory translates a compatible Altherma controller's P1P2 connection into Modbus RTU. Use its input registers for read-only operating telemetry, and independent heat and electricity meters for measured performance.

Daikin Altherma 3 H HT indoor and outdoor heat pump units
  • Modbus RTU

Air-to-water heat pump

Ask an engineer

Compatibility

Compatible with EpiSensor Edge over Modbus RTU through a DCOM-LT/MB adapter

Daikin's ETVH16-E7 combination table lists EPRA14DV37 and DCOM-LT/MB for this exact indoor variant. Daikin's DCOM-LT/MB manual documents the P1P2-to-Modbus RTU interface and its read-only input-register map.

Confirm the ETVH16S18E6V7 and EPRA14DV37 nameplates, compatible Altherma LT master controller, fitted DCOM-LT/MB, P1P2 ownership, DCOM operating mode and available inputs. Do not substitute the older non-E7 ETVH16UE6V or assume a Daikin HomeHub EKRHH configuration shares this register map.

Connect it with

The exact E7 pairing and a compatible Altherma LT master controller have a commissioned DCOM-LT/MB in normal monitoring mode

  • Wired
  • Edge
  • Platforms
Air-to-water heat pump
Interface
Gateway
Edge
Output
Altherma 3 H HT ETVH16S18E6V7ETVH16S18E6V7 indoor controller
DCOM-LT/MBDaikin P1P2-to-Modbus RTU interface
ZGW-20 GatewayHosts Edge locally
EpiSensor EdgeModbus client + register map
Customer platformMQTT · API · files
P1P2
Modbus RTU over EIA-485
Runs locally
Optional onward data
DCOM-LT/MB is the Modbus slave, not the heat pump itself. Connect its P1P2 terminals to a compatible Altherma LT master controller and its three-wire EIA-485 side to a protected Modbus bus. Configure a unique DCOM address, 9600 baud, 8 data bits and one stop bit; read only input registers with FC04. Verify operating mode before interpreting the map. The customer-platform output is optional; Edge remains the local system of record.

Models

Download
ModelsInterfaceRoute into Edge
ETVH16S18E6V7E7 indoor hydronic unit with 180 litre domestic hot-water tankConnect the approved DCOM-LT/MB to a compatible Altherma master, then read its Modbus inputs.
EPRA14DV37Paired 14 class outdoor unit in Daikin's combination tableThe outdoor unit is not the Modbus endpoint in this arrangement.
DCOM-LT/MBP1P2 input, separate 15–24 VDC supply and EIA-485 Modbus RTU slave outputTreat its register map and commissioning mode as the source of controller telemetry. It can also write controls; this guide approves reads only.

Specifications

The Daikin combination table names the ETVH16S18E6V7 indoor unit, EPRA14DV37 outdoor unit and DCOM-LT/MB accessory. This exact E7 suffix matters: a similarly named older indoor variant is not the same interface case.1

System identity
ETVH16S18E6V7 indoor plus EPRA14DV37 outdoor, as listed in the combination table1
Interface accessory
DCOM-LT/MB on compatible controller P1P2; separate 15–24 VDC supply12
Field bus
Two-wire EIA-485 Modbus RTU, 9600 baud, 8 data bits, one stop bit; DCOM is the slave2
Worked read
FC04, zero-based input offset 31: compressor run, 0 off or 1 on, in standard mode2
Temperature decode
FC04 input offset 42: signed 16-bit return-water temperature divided by 100 °C, in standard mode2
Invalid values
32767 unsupported; 32766 unavailable; 32765 waiting for value2
Performance boundary
Independent heat and electricity meters are needed for measured COP or SPF2

Interface

Documented measurements and integration boundaries for Altherma 3 H HT ETVH16S18E6V7.

  • In the manual's standard mode, FC04 input offset 31 reports compressor run and offset 32 reports booster-heater run. Confirm each against the installed controller before accepting a point.
  • Standard-mode input offsets 40 and 42 report leaving-water and return-water temperatures. Decode signed temp16 values as degrees Celsius divided by 100; validate them against the controller display.
  • The DCOM manual uses zero-based register offsets, not 3xxxx labels. Unsupported, unavailable and waiting values are 32767, 32766 and 32765 and must not enter a temperature or energy calculation.
  • Controller values do not establish delivered heat or whole-system COP. Independently meter thermal output and all electrical loads included in the chosen system boundary.
  • No operation-mode, setpoint, DHW, weather compensation or smart-grid write is approved here. DCOM's writable holding registers remain under the commissioned heating controller.

Assessment

ETVH16S18E6V7 with EPRA14DV37, compatible Altherma master and installed DCOM-LT/MB in standard mode. No write or flexibility control is approved.

InteroperabilitySupported with conditions
The exact E7 combination table includes DCOM-LT/MB, whose documented RTU inputs are readable by a Modbus master.12
AccuracyLimited
Operating temperatures and states are available; heat output and complete electricity require external meters for COP.2
SecurityLimited
The physical EIA-485 bus can be kept within the plant room, but the Modbus RTU link has no documented authentication and writable functions must be excluded.2
ReliabilitySupported with conditions
The DCOM documents master-synchronisation status and explicit unsupported, unavailable and waiting return values for quality handling.2
RuggednessNot yet assessed
The DCOM manual gives environmental limits, but no installation location or enclosure evidence was supplied.2
ScalabilityLimited
The RTU bus permits multiple addressed devices, but each heat pump's controller, DCOM and independent meter boundary need a commissioned design.2
LifecycleSupported with conditions
Daikin publishes both the E7 accessory combination and a DCOM register/manual contract, which can be checked against later revisions.12

Setup

Read return-water temperature from DCOM-LT/MB

The DCOM-LT/MB reference manual lists return-water temperature at input-register offset 42 in standard mode. This is a single read from the DCOM slave, not a command to the heat pump.

Target
Fitted DCOM-LT/MB slave address; 9600 baud, 8 data bits, no parity, one stop bit
Function
FC04 Read Input Registers
PDU start
42 decimal (0x002A) as a zero-based offset; Modicon 30043
Length
1 register
Decode
Signed 16-bit temp16 divided by 100, in degrees Celsius; 0x108B would mean 42.35 °C
Unavailable
32767 unsupported, 32766 unavailable, 32765 waiting; exclude all three before scaling

Acceptance: Compare the returned temperature with the local controller at the same moment. If the code is unavailable or waiting, check DCOM standard mode and its P1P2 synchronisation before adjusting the address. This is a manual-based starting read, not a physical test by EpiSensor.

  1. Verify the installed pair

    Record the ETVH16S18E6V7 and EPRA14DV37 nameplates, indoor controller revision, installed accessories and site heating-control owner. Use Daikin's combination table for this exact E7 configuration.

  2. Check the DCOM topology

    Confirm the fitted DCOM-LT/MB, its separate power supply, short P1P2 link to a compatible Altherma LT master and three-wire EIA-485 bus. Record its DIP-selected slave address and operating mode.

  3. Commission a bounded read

    With the heating contractor present, read standard-mode FC04 input offset 31 for compressor state and offset 42 for return-water temperature. Confirm the client uses zero-based offsets, compare both with local operation and reject unavailable or waiting codes.

  4. Measure performance separately

    Select the heat and electricity meter positions before reporting COP or SPF. Include pumps and auxiliary heaters when they fall inside the declared electrical boundary; align sampling periods.

Common questions

Does ETVH16S18E6V7 have a native Modbus port?
The documented path uses the separate DCOM-LT/MB accessory on a compatible controller's P1P2 connection. The DCOM is the Modbus RTU slave; do not connect Edge to the heat pump as if the outdoor unit were a Modbus server.12
Which DCOM registers are safe to read first?
In the manual's standard mode, FC04 offset 31 reports compressor run and offset 42 reports return-water temperature as signed hundredths of a degree Celsius. Check the DCOM mode and zero-based addressing, then compare the readings with local operation.2
Can the DCOM values prove heat-pump COP?
No. The DCOM map supplies controller operating values. Meter delivered heat and the chosen electrical boundary independently over the same periods before calculating COP or SPF.2

Sources

  1. Altherma 3 H MT and HT combination table and options, ECPEN22-767A (opens in a new tab) (PDF) Daikin
  2. DCOM-LT/MB reference manual (opens in a new tab) (PDF) Daikin
  3. DCOM-LT/MB product information (opens in a new tab) Daikin

Further reading

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