The IntesisBox General System Control is a Modbus RTU gateway template for controlling generic HVAC systems through an Intesis (HMS Networks) IntesisBox protocol translator. The gateway bridges proprietary HVAC communication protocols to Modbus RTU over RS-485, exposing five holding registers (H:0 through H:4) for system power control, temperature monitoring, and operating mode selection.
The template covers the base control set for any IntesisBox-connected HVAC system: system ON/OFF switching, outdoor ambient temperature, outgoing (supply) and ingoing (return) water temperatures, and a 6-mode operating mode selector supporting None, Heat, Heat/Tank, Tank, Cool/Tank, and Cool.
Hardware connection
Gateway overview
The IntesisBox gateway acts as a protocol translator between the HVAC system’s native communication bus and Modbus RTU. The gateway connects to the HVAC unit via the manufacturer’s proprietary interface and provides a standard RS-485 Modbus RTU interface for TapHome.
Technical specifications
- Protocol: Modbus RTU Slave, RS-485
- Baud rate: 9600, no parity, 1 stop bit, 8 data bits
- Default Slave ID: 1 (configurable via import parameter)
- IP Address parameter: 192.168.0.1 (for Modbus TCP bridging scenarios)
RS-485 wiring
Connect the IntesisBox RS-485 terminals to TapHome using a 3-wire connection:
- A+/D+ on IntesisBox to A+/D+ on TapHome RS-485
- B-/D- on IntesisBox to B-/D- on TapHome RS-485
- GND to GND on TapHome power supply (mandatory)
Cable specification:
- Type: twisted pair, shielded recommended
- Max length: 500 m (RS-485 standard)
- Use a twisted pair for A+/B- and a third wire for GND
Important – Grounding
The GND wire must be connected between the IntesisBox gateway and the TapHome power supply. Without proper grounding, communication errors may occur.
Configuration
Slave ID
The default Modbus Slave ID is 1. During template import in TapHome, the Slave ID can be changed via the import parameter. If multiple IntesisBox gateways are on the same RS-485 bus, each must have a unique Slave ID.
MAPS configuration software
The IntesisBox gateway is configured using the Intesis MAPS software (v1.5+). MAPS allows mapping additional registers beyond the base H:0–H:4 set depending on the specific HVAC protocol being bridged (BACnet, KNX, LonWorks, etc.). The TapHome template covers only the standard 5-register control set.
Device capabilities
System power control
- System ON/OFF (H:0) – turns the HVAC system on or off. Uses write-not-equal logic (MODBUSWNE) to avoid unnecessary writes when the state has not changed.
Temperature monitoring
The template provides three temperature readings from holding registers:
- Outdoor Temperature (H:1) – outdoor ambient temperature in degrees C. Read/write capable – the write function can provide an external temperature reference to the HVAC system. Uses Int16 data type to support negative temperatures.
- Outgoing Water Temperature (H:2) – supply water temperature in degrees C from the HVAC system. UInt16 data type (no negative values expected for supply water).
- Ingoing Water Temperature (H:3) – return water temperature in degrees C from the HVAC system. UInt16 data type (no negative values expected for return water).
Operating mode
- Operating Mode (H:4) – selects the HVAC operating mode with 6 available values:
| Value | Mode | Description |
|---|---|---|
| 0 | None | No active mode |
| 1 | Heat | Heating only |
| 2 | Heat/Tank | Heating with domestic hot water tank |
| 3 | Tank | Domestic hot water tank only |
| 4 | Cool/Tank | Cooling with domestic hot water tank |
| 5 | Cool | Cooling only |
The mode selector is typical for heat pump systems with domestic hot water (DHW) tank support, allowing combined heating/cooling with tank operation.
Additional capabilities
The IntesisBox MAPS configuration software allows mapping additional registers beyond H:0–H:4 depending on the specific HVAC protocol being bridged. These extended registers are not part of the current TapHome template but can be added as custom Modbus devices if needed.
Troubleshooting
No Modbus communication
- Check RS-485 cables:
- A+/D+ correctly connected to A+/D+ on TapHome
- B-/D- correctly connected to B-/D- on TapHome
- GND connected to TapHome power supply ground – most common issue
- Verify the Modbus Slave ID matches the import parameter in TapHome
- Confirm TapHome is set to: 9600 baud, no parity, 1 stop bit
- Check that the IntesisBox gateway is powered and the HVAC system is connected
Temperature readings showing incorrect values
- Verify the HVAC system is providing data to the IntesisBox gateway via the proprietary bus
- Check the MAPS configuration for correct register mapping
- Note that Outdoor Temperature uses Int16 (supports negative values) while water temperatures use UInt16 (positive only)
Operating mode not changing
- Confirm the HVAC system supports the selected mode (not all systems support all 6 modes)
- Check for mode conflicts – some HVAC systems may reject mode changes while actively operating
- Verify the IntesisBox gateway has write access to the HVAC system (some configurations may be read-only)
