An ESP32 component to communicate with Broan, Nutone, Venmar, and VanEE ERVs via their rs485 interface.
The protocol is documented here
Currently this project is stable, but may be missing some advanced features from certain models. If there is a feature you'd like added, please open an issue. We may need packet capture from a unit with this functionality.
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We currently don't have a good range of what does and don't work, but it's currently believed that all Broan, Nutone, and VanEE ERVs that have rs485 inputs probably work. The easiest way to check is to see if your unit supports the VTTOUCHW (All three brands have a version of this interface, they are all presumed to be the same)
HRVs have been reported to work as well, but tend to support fewer features. You can safely remove sensors from the yaml that your device does not support.
- You will need an esphome device that can communicate over rs485. Some devices come with this out of the box (waveshare esp32-s3-relay-6ch), or you can just buy an external tranceiver and wire it to the uart of your choice. Note that the waveshare device listed earlier is much easier to use than most, as it has automatic flow control and can be powered directly from the 12v output on your ERV. If you use a different device and make a working, stable configuration, please open an issue so we can start building a list with configuration files.
- This library does not coexist with other serial wall remotes. This is a software limitation on the ERV itself, it will only ever respond to one device on the bus. It's theoretically possible to MITM a remote but that's outside the scope of this component.
- You will ideally want to power this directly from the 12v output on the erv itself. this isn't a hard requirement, but it simplifies things a lot. If the ERV completes the handshake with the esp32 and it later goes away, the ERV will eventually drop into an error state and shut down, so it's just one less point of failure.
Near the control interface on the ERV, look for a green terminal block that has D+, D-, and GND on it (typically a 6 terminal block that includes 12V, LED, and OVR). Connect the D+, D-, and GND connectors to your RS485 tranceiver. Ideally you can also use the +12v but very few ESP32s are set up to handle input voltages above 5V to check with your spec sheet first. If not, just use a USB cable and wall charger. If you go this route, you may need to additionally run a wire from the GND terminal on the ERV to the GND pin on the esp32, but this will depend on how your rs485 tranceiver is set up. Only do this if you're getting unexplained communication errors or crashes.
Some rs485 trancevers have a jumper for the terminating resistor, some do not. In my case I found I did not need a termination resister, but you may need one. Try enabling this, or adding a resistor manually across the terminals on the ESP32 side, if you have communication issues. You'll know if you flip these because you'll see a bunch of spew about alignment errors and unknown commands.
Also be aware some RS485 devices will label their pins A and B instead of D+ and D-. Somewhat confusingly, A is D- and B is D+
- Setting fan mode (Standby, Min, Max, Intermittent, Turbo, Override, and Med, which is treated as manual control)
- Setting fan speed in manual mode
- Humidity control mode
- Intake temperature
- Filter life left
- Fan CFM
More features will be added as time allows. I've documented many fields that aren't supported yet. If there's a specific feature you want prioritized, open an issue. This project is at a point where it "works for me" so I don't have a lot of guiding light on what else should be added without external input.
In Humidity Control Mode, the controller sets a target humidity level and the ERV automatically runs if the humidity is above this level. The ERV does not have a humidity sensor - the current humidity reading is sent periodically from the controller. Since we are replacing the original controller, we need to send current humidity readings from the ESP device. This can be done from a lambda in your ESPHome config calling the setCurrentHumidity() function. For an example configuration, see the humidity_control_sample.yaml configuration in the examples directory.
To use humidity control mode once it is enabled, set the desired humidity with "Humidity Setpoint", and then turn on the Humidity Control switch.
Q: I see errors about failed communication
A: This could be a lot of things.
- If you're getting timeouts, it's probably the yaml being misconfigured. A lot of rs485 devices want a flow control pin, which needs to be specified (check your device's datasheet)
- If you see it getting data but complaining about alignment and unknown commands, it's likely either you swapped the +/- wires, or the communication is very weak. Double check that you wired up the ground wire correctly, and try adding or removing esp side termination.
Q: Why doesn't it support X?
A: Not everything is actually exposed via the rs485 interface. I may need dumps from a unit with the feature you're requesting, or it might already be mapped and just needs to be plumbed though to Home Assistant. Feel free to open an issue or PR
Q: What if I still want wall controls?
A: You can use the aux remotes, those use the dry contact interface which is a hard override. The fan mode will indicate "ovr" (override) when these controls are used. This is how Broan bypasses the protocol limitation. Alternatively, look at something like the Sonoff NSPanel and control the device via Home Assistant instead.
Add this to an existing config.
external_components:
- source:
type: git
url: https://github.com/nspitko/broan_erv_uart
ref: main
components: [ broan ]
uart:
id: rs485
tx_pin: GPIO17 # Change these to match your rs485 tranceiver. 17/18 is txd1/rxd1
rx_pin: GPIO18
baud_rate: 38400
rx_buffer_size: 2048
#debug:
# direction: BOTH
# dummy_receiver: false
# sequence:
# - lambda: UARTDebug::log_hex(direction, bytes, ' ');
broan:
uart_id: rs485
select:
- platform: broan
fan_mode:
name: "fan mode"
number:
- platform: broan
# Speed as a ratio of min vs max speed. Eg, if your MIN is 20 CFM and your MAX is
# 40 CFM, 50% means medium rill be at 30 CFM
fan_speed:
name: "fan speed"
# How many seconds ON per hour in int mode (eg, a value of 20 means the ERV will run
# 20 minutes on 40 minutes off every hour )
intermittent_period:
name: "Intermittent Period"
sensor:
- platform: broan
# As reported by the ERV, in watts
power:
name: Power draw
# Intake air temperature. This will generally read high
temperature:
name: Temperature
# In Days
filter_life:
name: Remaining Filter life
# CFM values as reported by the ERV
supply_fan_cfm:
name: "Supply fan CFM"
exhaust_fan_cfm:
name: "Exhaust fan CFM"
# Fan motor RPM values
supply_fan_rpm:
name: "Supply fan RPM"
exhaust_fan_rpm:
name: "Exhaust fan RPM"
# Not all ERVs have these sensor, remove if you don't get readings from it.
# Exhaust air temperature.
temperature_out:
name: Temperature Out
text_sensor:
- platform: broan
# If there is a major fault, it will be indicated here. Else "OK"
fault_code:
name: "Fault code"
# Same as above, but for warnings.
warning_code:
name: "Warning code"
# Active mode. Indicates what the fans are currently doing
active_mode:
name: "Active Mode"
# Potentially useful for development
#model: { name: "Model" }
#firmware: { name: "Firmware" }
#firmware_version: { name: "Firmware Version" }
#hardware_revision: { name: "Hardware Rev" }
button:
- platform: broan
# Resets filter life to 7884000 seconds / 3 months (Default behavior)
filter_reset:
name: Filter reset