If you build air handlers, heat pumps, fan-coil or rooftop packages, the wall device is the last thing a building owner touches and the first thing they blame. A generic thermostat under your logo rarely survives an RFQ. An OEM Modbus room unit is the other path: a branded, host-driven wall UI that already speaks RS-485 and can sit on your BMS or cloud stack without you starting a glass-and-firmware project from zero.
Alledio’s Room Unit is that class of device. It is designed and manufactured in Slovenia for HVAC original equipment manufacturers, not for one-off installer purchases. The host (your controller, AHU board, or BMS) still runs the plant. The wall unit is the face, the sensors, and the bus citizen.
Who this is for
This article is for OEM product managers, controls engineers, and BMS device makers who need a branded wall interface at production volume.
Typical applications map to real OEM lines: air handling units, residential and commercial heat pumps, VAV and rooftop units, ductless mini-splits, VRV, chillers, boilers and domestic hot water, plus actuator-facing UIs. Offices, schools, hotels and museums are named end markets. Installers and system integrators cannot buy Alledio direct. The commercial model is high-MOQ OEM (the site cites an order of magnitude around 5,000 units). A sample is an NDA conversation, not a webshop.
If you need standalone I/O and application logic in the same family, that is the Room Controller, not this SKU.
How to write the RFQ for an OEM Modbus room unit
Buyers lose months when the RFQ mixes “pretty thermostat,” “room controller,” and “IAQ sensor.” Use language the factory can quote.
Ask for:
- A slave Modbus RTU device on RS-485 (half-duplex), baud rates you already use (Alledio lists 9600 through 115200, parity none/even/odd, software-defined termination). Master mode only if you truly need it.
- Host-driven architecture: setpoints, fan, schedule and alarms on the glass; plant algorithms on your board.
- Default T/RH, with optional VOC, CO2, pressure and presence as orderable variants.
- Power that matches your wall: 12–42 V DC (24 V recommended) or 24 VAC ±25%. Do not assume 230 VAC. That is the thermostat family.
- Housing 98 × 98 × 23 mm, IP20, 3.5" capacitive LCD (480 × 320), ABS plus scratch-resistant glass.
- Branding scope: exterior logo, UI colours, widgets, firmware, and whether Wi-Fi (2.4 GHz) and partner MQTT/REST are in scope.
- Compliance you can defend: RED 2014/53/EU including the cybersecurity delegated act, RoHS, and a 10-year security-update window.
State MOQ, sample count, NRE for firmware, and who owns the register map. Ask for the ICD with the mechanical drawing.
Host vs wall: who runs the plant
An OEM Modbus room unit is not a miniature DDC. The wall device shows temperature and humidity, takes a setpoint, exposes fan speed or Auto, can hold a weekly schedule, and can surface notifications. Recuperation views or a sanitary hot-water shortcut are firmware options, but they are still requests to a host unless you specified the Room Controller.
That split is the point. You keep control IP, sequencing and safety on the board you already certify. Occupants get a 3.5" panel that feels like your brand. Wi-Fi is for OTA and, for verified partners, MQTT or REST. Bluetooth 5 LE is ready; the GATT map is yours. None of that replaces Modbus RTU on the copper pair.
Why a 3.5 inch OEM HVAC touch panel belongs on the wall
A 3.5 inch OEM HVAC touch panel is large enough for temperature, humidity, air quality and a one-tap absence, and small enough to stay in a 98 mm square. Capacitive touch plus a brightness sensor keeps the glass readable in a lobby and quiet in a bedroom.
Colourways (white, black, silver, plus custom) let the same electronics follow a hotel, school or heat-pump indoor line. OEM customisation covers logo, UI, widgets, hardware and firmware. You pay for the delta, not for reinventing a certified radio and a mould.
The Room Unit was on the floor at Smart Building Expo Milan 2025 as a branded HVAC wall UI, not a DIY thermostat.
Protocols that actually ship
On the Room Unit: Modbus RTU over RS-485 (slave default; master on request); Wi-Fi 2.4 GHz (STA/AP), OTA, HTTPS; Bluetooth 5 LE per client spec; REST and MQTT for authorised partners. The product page also lists a 0–10 V analogue output as a connectivity option for valves, dampers or EC fans.
Not a catalogue SKU here: native BACnet on this product (native BACnet lives on the Multi-Sensor family); KNX; 230 VAC relays (Thermostat / Room Controller).
If the RFQ says “BACnet wall UI,” do not force this SKU. Budget an OEM protocol add-on, or use the Multi-Sensor for field sensing and keep the Room Unit as the occupant display.
Product proof
| Topic | Published spec |
|---|---|
| Display | 3.5" LCD, 480 × 320, capacitive touch, auto brightness |
| Sensors (standard) | Digital temperature and humidity |
| Sensors (optional) | VOC, CO2 (400–5000 ppm), pressure, presence |
| Bus | RS-485 Modbus RTU, 9600–115200 baud |
| Power | 12–42 V DC or 24 VAC ±25%; ~0.3 W at 50% brightness |
| Mechanics | 98 × 98 × 23 mm, 150 g, IP20 |
| Origin | Slovenia, EU |
| Security support | 10-year update window |
FAQ
Can an installer or systems integrator buy one from a webshop?
No. Alledio sells to OEMs. Installers and SIs get devices through the OEM’s channel. OEMs ask for a sample under NDA.
Does the Room Unit run the plant?
No. It is host-driven. Sequences and safeties live on your controller unless you specified the Room Controller.
Is there a KNX catalogue SKU?
KNX is not listed as a shipping protocol on alledio.com. Other buses are OEM firmware or hardware work, quoted separately.
What to do next
Start on the Alledio Room Unit page, then open an OEM conversation for logo, UI, firmware and samples. Bring baud rate, power, sensor options and MOQ.
