DM-OT2 – The OpenTherm/plus converter

The DM-OT2 is a converter of the RS485 interface (with MODBUS RTU or ARION protocol) to the OpenTherm/plus (OT/+) interface. The converter operates as a control unit with the OpenTherm interface in the master role and enables control of several types of boilers. The converter communicates with the boiler continuously, independently from the communication with the control system.

Up to 63 DM-OT2 converters can operate at the same time in an RS485 network. With the MODBUS protocol selected, the converter allows reading or writing any available DATA-ID offered by peripherals to the OpenTherm/plus network.

This converter replaces both older versions – DMM-OT (MODBUS) and DM-OT (ARION).


Conversion type RS485 <-> OpenTherm
Mounting 35-mm DIN rail
RS485 communication protocol MODBUS RTU / ARION (selectable)
Transfer rate 9,600 bps to 115,200 bps
Galvanic isolation of RS485 Yes
Number of stations per RS485 network 63
Power 20 V DC to 30 V DC
Operation temperature -40 °C to 70 °C
Dimensions (w × h × d) (54 × 90 × 61) mm
Document File
DM-OT2 Data sheet dm-ot2_d_en_100.pdf
Drawing symbol
ePLAN macro
Operation manual dm-ot2_g_en_103.pdf

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