Westaflex WAC 350 & 351
Controls Westaflex ventilation systems via Modbus RTU
This template connects Westaflex WAC 350 and WAC 351 ventilation units to ModbusCloud via Modbus RTU. It reads temperatures, humidity, fan level, and alarm states while allowing control of supply air temperature and target temperature setpoints.
- Protocol
- Modbus RTU
- Connection
- RS485, 19200 baud
- Registers
- 20, read and write
- Brand
- Westaflex
- Key readings
- Outside temperature · Supply air temperature · Extract air temperature · Exhaust air temperature · Extract air humidity · Fan level
- Available commands
- Supply air temperature · Target temperature
- Compatible models
- WAC 350 · WAC 351
- Last updated
Registers (20)
20 read, 2 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| outside temperature | °C | Read | |||
| extract air temperature | °C | Read | |||
| supply air temperature | °C | Read and write | |||
| extract air humidity | % | Read | |||
| fan level | % | Read | |||
| target temperature | °C | Read and write | |||
| Alarm extract sensor | Read | ||||
| fan | Read | ||||
| Alarm set temperature | Read | ||||
| fire Alarm | Read | ||||
| filter Message | Read | ||||
| Frost protection | Read | ||||
| Alarm fan | Read | ||||
| Alarm supply voltage | Read | ||||
| Alarm exhaust air sensor | Read | ||||
| Alarm return water | Read | ||||
| Alarm outdoor sensor | Read | ||||
| reheating | Read | ||||
| exhaust air temperature | °C | Read | |||
| outdoor air flap | Read |
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Use cases
- Monitor supply and extract air temperatures on a live dashboard to verify heat recovery performance.
- Adjust target temperature setpoints remotely when building occupancy changes seasonally.
- Create an alert when extract air humidity exceeds a threshold to detect moisture problems early.
- Track fan level changes over time to identify unusual ventilation patterns or filter degradation.
- Set up notifications for frost protection or fire alarm states to respond quickly to critical events.
- Compare outside and exhaust air temperatures to evaluate heat exchanger efficiency over time.
Installation
Wire the Modbus RTU connection (A and B terminals) from the Westaflex WAC 350 or WAC 351 to the RS-485 port on your ModbusCloud Gateway.
Set the baud rate on the gateway to 19200 to match the default communication settings of the Westaflex unit.
Configure a unique Modbus slave address on the ventilation unit if multiple devices share the same RTU bus.
Import the Westaflex WAC 350 and 351 template from the ModbusCloud template library into your project.
Assign the correct slave address in the template settings to match the address configured on the ventilation unit.
Verify communication by checking live readings for outside temperature and fan level in the ModbusCloud dashboard.
Things to watch for
Why do I get incorrect values when reading certain registers?
The WAC 350 and WAC 351 share some register addresses for different functions. For example, address 0 serves both supply air temperature and frost protection. Make sure you are using the correct Modbus function code to distinguish between read and write operations on these shared registers.
The gateway cannot communicate with the ventilation unit. What should I check?
Verify that the baud rate is set to 19200 on both the gateway and the ventilation unit. Also confirm the RS-485 wiring polarity (A to A, B to B) and check that the configured slave address matches on both sides.
Can I connect multiple Westaflex units on one RTU bus?
Yes, as long as each unit has a unique Modbus slave address. Assign distinct addresses on each ventilation unit and create a separate template instance for each device in ModbusCloud.
Do I need a termination resistor on the RS-485 bus?
If the Westaflex unit is at the end of the bus or the cable run exceeds a few meters, it is recommended to enable or install a 120 ohm termination resistor at both ends of the bus to ensure reliable communication.
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