If you build air handlers or heat pumps, 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, without a glass-and-firmware project from zero.
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Alledio’s Room Unit is that class of device. It is designed and manufactured in Slovenia for HVAC original equipment manufacturers. The host 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 DHW, plus actuator-facing UIs. End markets include offices, schools, hotels and museums. Installers and system integrators cannot buy Alledio direct. The commercial model is high-MOQ OEM. The usual MOQ is 1,000 pcs, and it is negotiable. 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. Keep that split in the RFQ so purchasing does not mix a display with a controller.
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, and attach the mechanical drawing with the ICD.
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.
- An OEM wall UI flush mount in a 98 × 98 × 23 mm, IP20 housing, 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, who owns the register map, and who writes the slave ID plan. Ask for termination as a software setting, not a field modification. Specify the cable class you already pull (typically a shielded twisted pair) and the maximum stub length your BMS already allows. If several Room Units share one segment, write the addressing table in the RFQ so commissioning is not invented on site.
Also name the documents you want back: ICD, register list, mechanical drawing, and a short integration note for your controller team. That pack is what turns a pretty glass into a line item your plant firmware can use.
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.
On an AHU line, that usually means the board already certified for safeties keeps supply-air limits, frost, and fire-mode. On a heat pump, the outdoor unit and hydronic logic stay on your controller; the wall unit only publishes occupancy, setpoint, and sensor values. On a fan-coil or VAV box, fan and damper commands still leave your host, even if the occupant only ever touches the glass.
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.
Write the host contract in one page: which registers are read-only sensors, which are writable setpoints, and which bits are alarms. If the wall unit can enter an unoccupied or boost state, say whether that is a local timer or a request the host must honour. Ambiguity here is how field teams later “fix” a unit by writing plant logic into a display.
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.
Flush depth matters as much as the glass. The 23 mm body is meant to sit in a standard European wall box, not to hang as a surface brick. If your indoor unit already has a 98 mm cut-out language, you can keep that language across a hotel, an office, and a residential heat-pump controller without drawing a new fascia for each SKU.
The Room Unit was on the floor at Smart Building Expo Milan 2025 as a branded HVAC wall UI, not a DIY thermostat. How the room feels, not only how the glass looks, is also the thread of Beyond design: it’s how it feels.
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 (OEM Modbus relay thermostat / Room Controller). For a branded three-speed FCU face on that family, see the white label FCU thermostat.
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. If the RFQ says KNX, treat that as a separate firmware or hardware quote, not as a hidden checkbox on this page.
For Modbus itself, write the things that break commissioning: slave vs master, baud, parity, termination, and whether the host expects holding registers, input registers, or both. Alledio can ship a slave that matches a map you already use. It will not guess your map if the RFQ only says “Modbus.”
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 |
Those numbers are what you can put in a customer PDF today. Confirm any cell you cannot see on the current datasheet before you lock an RFQ. Comfort copy on the site is specific: the unit manages how the room feels (setpoint, fan, schedule, humidity and air-quality visibility) while the host and the plant do the energy work.
FAQ
What power does the Room Unit take?
12–42 V DC (24 V recommended) or 24 VAC ±25%. Do not copy a 230 VAC thermostat line into this RFQ. That is a different family.
Who owns the register map?
You do. Write slave vs master, baud, parity, termination, and the ICD in the RFQ. Alledio can match a map you already use. It will not guess if the RFQ only says “Modbus.”
Does the Room Unit run the plant?
No. It is host-driven. Occupants see setpoints and sensors on the glass. Sequences and safeties stay on your controller, unless you specified the Room Controller.
Can we get samples?
Yes. Samples are available with demo firmware or test firmware, under NDA. This is not a webshop SKU. Start the conversation on /oem.
What is the MOQ?
The usual MOQ is 1,000 pcs, and it is negotiable. If you order several different versions of Room Unit or Room Controller and the combined quantity is over 1,000 pcs, we can go down to 500 on a version.
Can an installer buy this from a webshop?
No. Alledio sells to OEMs. Installers and SIs get units through your channel.
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. That is the shortest path from an RFQ sentence to a wall UI that already speaks Modbus.
