Buderus (Bosch Thermotechnology) · Boiler
SSB condensing boiler Modbus register map
Default configuration
- Protocol
- RS485
- Port
- 502
- Unit ID
- 1
- Addressing
- 0-based
- Byte order
- Big endian
- Word order
- High word first
- Baud rate
- 9600
- Parity
- None
- Data bits
- 8
- Stop bits
- 2
This device has an RS-485 interface. Reach it through a Modbus RTU-to-TCP gateway, configured with the factory serial settings above.
Register map
| Address | Count | Name | Type | Unit | Scale | Access |
|---|---|---|---|---|---|---|
| 98 | 1 | Unit selection Bit0: 0 = °C, 1 = °F. Bit1: 0 = bar, 1 = psi. Writing requires the write-enable bit in register 99. | UInt16 | - | 1 | RW |
| 99 | 1 | Control register Bit0 = write enable (cleared automatically after a write and after 4 s without communication). Bit14 = controller reset (only accepted in lockout). All other bits must be 0. | UInt16 | - | 1 | RW |
| 100 | 1 | State Burner state code; the document's state table (Tab. 10) lists the state numbers 0-23. | UInt16 | - | 1 | R |
| 101 | 1 | Status Operating-status code; the document's status table (Tab. 11) lists the status numbers (0, 10, 14-22). | UInt16 | - | 1 | R |
| 102 | 1 | Error code Current error number; the document's error table (Tab. 12) lists the lockout and blocking error numbers. 0 = no error. | UInt16 | - | 1 | R |
| 110 | 1 | CH pump Central-heating pump output, 0-100 %. | UInt16 | % | 1 | R |
| 111 | 1 | DHW pump Domestic-hot-water pump output, 0-100 %. | UInt16 | % | 1 | R |
| 112 | 1 | General pump General (system) pump output, 0-100 %. | UInt16 | % | 1 | R |
| 120 | 1 | Supply temperature Flow temperature, factor 10 in the document (value 650 = 65.0). Unit follows register 98 (0.1 °F when set to °F). | Int16 | °C | 0.1 | R |
| 121 | 1 | Return temperature Return-water temperature, factor 10 in the document. Unit follows register 98. | Int16 | °C | 0.1 | R |
| 122 | 1 | DHW temperature Domestic-hot-water temperature, factor 10 in the document. Unit follows register 98. | Int16 | °C | 0.1 | R |
| 123 | 1 | Flue gas temperature Flue-gas temperature, factor 10 in the document. Unit follows register 98. | Int16 | °C | 0.1 | R |
| 124 | 1 | System (heat exchanger) temperature Heat-exchanger temperature, if available. Factor 10 in the document. | Int16 | °C | 0.1 | R |
| 125 | 1 | Outside temperature Outdoor temperature, if available. Factor 10 in the document. | Int16 | °C | 0.1 | R |
| 140 | 1 | Firing rate (power output) Current firing rate, 0-100 %. | UInt16 | % | 1 | R |
| 142 | 1 | Flame (ionisation) current Flame ionisation current, factor 10 in the document. | UInt16 | µA | 0.1 | R |
| 200 | 1 | Successful ignition counter Number of successful ignitions, 0-65536, resolution 16 in the document. | UInt16 | - | 1 | R |
| 201 | 1 | Failed ignition counter Number of failed ignitions. | UInt16 | - | 1 | R |
| 202 | 1 | Flame failure counter Number of flame failures. | UInt16 | - | 1 | R |
| 203 | 1 | Burn hours CH Accumulated burner hours for central heating. | UInt16 | h | 1 | R |
| 204 | 1 | Burn hours DHW Accumulated burner hours for domestic hot water. | UInt16 | h | 1 | R |
| 220 | 1 | Lockout history 1 (oldest entry) Lockout error number of the first stored lockout, see the error table. | UInt16 | - | 1 | R |
| 221 | 1 | Lockout history 2 Second stored lockout error number. | UInt16 | - | 1 | R |
| 222 | 1 | Lockout history 3 Third stored lockout error number. | UInt16 | - | 1 | R |
| 223 | 1 | Lockout history 4 Fourth stored lockout error number. | UInt16 | - | 1 | R |
| 224 | 1 | Lockout history 5 Fifth stored lockout error number. | UInt16 | - | 1 | R |
| 225 | 1 | Lockout history 6 Sixth stored lockout error number. | UInt16 | - | 1 | R |
| 226 | 1 | Lockout history 7 Seventh stored lockout error number. | UInt16 | - | 1 | R |
| 227 | 1 | Lockout history 8 Eighth stored lockout error number. | UInt16 | - | 1 | R |
| 228 | 1 | Lockout history 9 Ninth stored lockout error number. | UInt16 | - | 1 | R |
| 229 | 1 | Lockout history 10 Tenth stored lockout error number. | UInt16 | - | 1 | R |
| 230 | 1 | Lockout history 11 Eleventh stored lockout error number. | UInt16 | - | 1 | R |
| 231 | 1 | Lockout history 12 Twelfth stored lockout error number. | UInt16 | - | 1 | R |
| 232 | 1 | Lockout history 13 Thirteenth stored lockout error number. | UInt16 | - | 1 | R |
| 233 | 1 | Lockout history 14 Fourteenth stored lockout error number. | UInt16 | - | 1 | R |
| 234 | 1 | Lockout history 15 Fifteenth stored lockout error number. | UInt16 | - | 1 | R |
| 235 | 1 | Lockout history 16 Sixteenth stored lockout error number. | UInt16 | - | 1 | R |
| 236 | 1 | Time after first lockout Hours between start-up and the first stored lockout. | UInt16 | h | 1 | R |
| 237 | 1 | Time after second lockout Hours recorded with the second stored lockout. | UInt16 | h | 1 | R |
| 238 | 1 | Time after third lockout Hours recorded with the third stored lockout. | UInt16 | h | 1 | R |
| 239 | 1 | Time after fourth lockout Hours recorded with the fourth stored lockout. | UInt16 | h | 1 | R |
| 240 | 1 | Time after fifth lockout Hours recorded with the fifth stored lockout. | UInt16 | h | 1 | R |
| 241 | 1 | Time after sixth lockout Hours recorded with the sixth stored lockout. | UInt16 | h | 1 | R |
| 242 | 1 | Time after seventh lockout Hours recorded with the seventh stored lockout. | UInt16 | h | 1 | R |
| 243 | 1 | Time after eighth lockout Hours recorded with the eighth stored lockout. | UInt16 | h | 1 | R |
| 244 | 1 | Time after ninth lockout Hours recorded with the ninth stored lockout. | UInt16 | h | 1 | R |
| 245 | 1 | Time after tenth lockout Hours recorded with the tenth stored lockout. | UInt16 | h | 1 | R |
| 246 | 1 | Time after eleventh lockout Hours recorded with the eleventh stored lockout. | UInt16 | h | 1 | R |
| 247 | 1 | Time after twelfth lockout Hours recorded with the twelfth stored lockout. | UInt16 | h | 1 | R |
| 248 | 1 | Time after thirteenth lockout Hours recorded with the thirteenth stored lockout. | UInt16 | h | 1 | R |
| 249 | 1 | Time after fourteenth lockout Hours recorded with the fourteenth stored lockout. | UInt16 | h | 1 | R |
| 250 | 1 | Time after fifteenth lockout Hours recorded with the fifteenth stored lockout. | UInt16 | h | 1 | R |
| 251 | 1 | Time after sixteenth lockout Hours recorded with the sixteenth stored lockout. | UInt16 | h | 1 | R |
| 500 | 1 | CH mode Central-heating mode. Writing requires the write-enable bit in register 99. | UInt16 | - | 1 | RW |
| 501 | 1 | DHW mode Domestic-hot-water mode. Writing requires write enable (register 99). | UInt16 | - | 1 | RW |
| 502 | 1 | CH set-point Central-heating set-point, factor 10 in the document. Unit follows register 98. | Int16 | °C | 0.1 | RW |
| 503 | 1 | DHW set-point Domestic-hot-water set-point, factor 10 in the document. Unit follows register 98. | Int16 | °C | 0.1 | RW |
| 504 | 1 | Reset curve boiler design Heating-curve boiler design temperature. Factor 10 in the document. | Int16 | °C | 0.1 | RW |
| 505 | 1 | Reset curve boiler mild weather Heating-curve boiler temperature at mild weather. Factor 10 in the document. | Int16 | °C | 0.1 | RW |
| 506 | 1 | Reset curve outdoor mild weather Heating-curve outdoor temperature at mild weather. Factor 10 in the document. | Int16 | °C | 0.1 | RW |
| 507 | 1 | Reset curve outdoor design Heating-curve outdoor design temperature. Factor 10 in the document. | Int16 | °C | 0.1 | RW |
| 508 | 1 | Warm weather shutdown Outdoor temperature above which heating stops. Factor 10 in the document. | Int16 | °C | 0.1 | RW |
| 509 | 1 | Reset curve boiler maximum Maximum boiler temperature on the heating curve. Factor 10 in the document. | Int16 | °C | 0.1 | RW |
| 510 | 1 | Reset curve boiler minimum Minimum boiler temperature on the heating curve. Factor 10 in the document. | Int16 | °C | 0.1 | RW |
| 511 | 1 | Night setback Night-setback value. Factor 10 in the document. | Int16 | °C | 0.1 | RW |
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Notes
Source: Buderus (Bosch Thermotechnology) "Modbus for Buderus SSB boilers - Installation and Service Instructions for Contractors", document 6720818450 (2015/10) US, sections 3 (configuration), 4 (holding registers) and 5 (state/status/error tables), https://www.bosch-homecomfort.com/us/media/country_pool/service/technical_guides/6720818450_ssb_boiler_modbus_installation_instructions_en_10.2015_us_us.pdf. Factory serial settings from section 3: Modbus RTU, 9600 bps, 8 data bits, no parity, 2 stop bits, slave address 1 (address, baud rate and stop bits are configurable with 894PB or LabVision; 2 stop bits is the default). Addressing: the document prints decimal and hexadecimal addresses that agree (98 = 0x0062); it says a client whose numbering starts at 0 uses the printed address unchanged, so the seed is zero-based. Values are 16-bit; the document's data-type table gives factor 10 for temperatures, voltage, pressure and flame current, so those rows use scale 0.1. Readings follow the unit selection register 98 (°C/°F, bar/psi). Writing to holding registers requires the write-enable bit (bit 0 of register 99) and is only honoured within 4 s. Omitted on purpose: the blocking-error history (260-291) and the per-dependent-burner blocks (300-339) are not seeded; all 16 lockout codes (220-235) and their 16 time stamps (236-251) are. The document itself warns that the internal error history is not in chronological order.