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SETECNA
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Rev. 01
Alessandro
Page: 8 di 10
14/09/2016
23/09/16 17.56
Gateway MODBUS-to-Opentherm MB-OTG
Technical manual
The mapping between Register/Coil and OpenTherm function is the following:
Readable Modbus Registers
(by using MODbus function 0x03)
Corresponding
Opentherm ID
Format
Register Number (address)
NOTES
Slave Config
3
2
Fault Flag (OEM Fault Code)
5
3
RBP Flags
6
4
Maximum boiler capacity (kW) /
Minimum Modulation Level (%)
15
5
Relative Modulation Level (%)
17
tenth of %
6
Water Pressure in CH Circuit (bar)
18
tenth of bar
7
Boiler Flow Water Temperature (°C)
25
tenth of °C
8
DHW Temperature (°C)
26
tenth of °C
9
Outside Temperature (°C)
27
tenth of °C
10
Return Water Temperature (°C)
28
tenth of °C
11
Boiler Exhaust Temperature (°C)
33
tenth of °C
12
Boiler Fan Speed Setpoint and Actual
Value
35
13
Electrical current through burner
flame (uA)
36
14
DHW Setpoint bounds
48
tenth of °C
15
CH Setpoint bounds
49
tenth of °C
16
Burner operation hours
120
integer number
17
CH Pump operation hours
121
integer number
18
Number of Communication Error on
Opentherm side
n/a
integer number
22
Opentherm communication failed
n/a
If=1,
communication KO
23
Writable MODbus register
(by using MODbus function 0x05)
CH Water temperature setpoint
1
tenth of °C
25
DHW Setpoint
56
tenth of °C
26
Maximum relative modulation level
setting
14
tenth of %
27
Readable Coils
(by using MODbus function 0x01)
Bit of Opentherm ID 0
Coil Number (address)
Fault indication
0 (reading)
0
CH Mode
1 (reading)
1
DHW Mode
2 (reading)
2
Flame Status
3 (reading)
3
Writable Coils
(by using MODbus function 0x05)
CH Enable
0 (writing)
48
DHW Enable
1 (writing)
49
