ModBus RTU Gateway
The ModBus RTU Gateway allows two way communication from the Building Management System (BMS) to any of our electronic HIU's, using the ModBus Protocol. This allows the building manager to read any of the parameters being monitored by the HIU electronics, such that plantroom controls can be adjusted to optimise the efficiency of the entire district heating system.
In order to work with the ModBus RTU Master, the suitable ModBus software will be required. For testing purposes we have used 'Simply Modbus master', a demo of which can be downloaded here.
Documents
Installation Sheet
 | Installation sheet Installation sheet for the Modbus RTU-Zero Gateway . |
Modbus Registers for HIUs
Version 1
These are the standard registers used for Modbus connection to HIUs.
Holding registers:
1: Pr Flow Temp [C] [x10]
2: Pr Diff Pressure [bar] [x100]
3: State [0-10] (See below)
4: PowerUpCounter [x1]
5: ErrorCounter [x1]
6: PressureModeAuto [0/1]
10: Setpoint DHW [C] [x10]
11: WarmupBoost [l/m] [x10]
12: EcoMode [0/1]
13: DHWAntiLegionella [0/1]
14: DHWEcoHeatTemp [C] [x10]
15: DHWEcoHeatTime [minutes] [x1]
20: DHW Flow Rate [l/m] [x10]
21: DHW Output Temp [C] [x10]
22: Pr Rtn Temp DHW [C] [x10]
23: Valve Position DHW [0-270] [x1]
24: Pr Flow Rate DHW [l/m] [x10]
25: DHW Volume [l]
30: DHReturnLimit [C] [x10]
31: HESupply [C] [x10]
32: PumpTimeout [s]
33: DHReturnLimit Enable [0/1]
34: CentralHeatingControl [0/1]
40: Room Thermostat [0/1]
41: CH Output Temp [C] [x10]
42: Pr Rtn Temp CH [C] [x10]
43: Valve Position CH [0-270] [x1]
44: Pr Flow Rate CH [l/m] [x10]
45: CH System Pressure [bar] [x100]
46: CH Pump [0/1]
50: PrePayShutOff [0/1]
Modbus Setup
| Address | 17 |
| Baud | 9600 |
| Data Bits | 8 |
| Parity | None |
| Stop Bits | 2 |
| Data Type | 16INT |
| Function Codes | 3 (read), 6 (write) |
Description of Register 3 - State 0-10
| No | Status | Description |
|---|---|---|
| 0 | INIT | Standard state |
| 1 | INIT_WAIT | |
| 2 | STANDBY | Heating |
| 3 | WARMUP | Start of hot water request |
| 4 | STEADYSTATE | Controlling of hot water temperature |
| 5 | CLOSING | End of hot water request |
| 6 | HOME_STEPPER | |
| 7 | ERROR | |
| 8 | ERROR_WAIT | System stays in this state for 20 Secs, then returns to INIT |
| 9 | PREPAYSHUTOFF | |
| 10 | PREPAYSHUTOFF_WAIT |
Version 2
Version 2 is for Heating Only Sub-Stations. Details are as per version 1 except for register values as below.
Holding registers:
1: Pr Flow Temp [C] [x10]
2: Pr Diff Pressure [bar] [x100] (if available)
4: PowerUpCounter [x1]
5: ErrorCounter [x1]
6: Alarm Count [x1]
7: Warning Count [x1]
30: Primary Return Limit [C] [x10] tHoLimit
31: Central Heating Setpoint [C] [x10] tSetCH
32: Pump Timeout [s] pumpTimeout
33: Primary Return Limit Enabled [0/1] enableHoLimit
34: Central Heating Enabled [0/1]
35: Primary Flow Rate Limit [l/m] fHCHLimit
36: Primary Return Limit and [C] bandHoLimit default 2
37: Setpoint Approach Temperature [C] tApproachCH default 3
40: Room Thermostat [0/1]
41: CH Output Temp [C] [x10]
42: Pr Rtn Temp CH [C] [x10]
43: Valve Position CH [0-100] [x10]
44: Pr Flow Rate CH [l/m] [x10]
45: CH System Pressure [bar] [x100]
46: CH Pump [0/1]
50: PrePayShutOff [0/1]
