HVAC OEMs that already run Modbus on the trunk do not need a BACnet gateway just to prove room air quality. A Modbus multi sensor OEM node puts temperature, humidity, VOC, CO2, pressure, and presence on one 87 × 87 mm wall device, with dew point, enthalpy, and density of moist air computed on board. The Alledio Multi-Sensor ANM line speaks Modbus RS-485 under your brand, is commissioned from a phone over NFC, and is built in Slovenia for OEM programmes - not webshop buyers.

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Who specifies a Modbus Multi-Sensor OEM node

This guide is for product managers, controls engineers, and BMS teams at HVAC and building-automation OEMs: AHU, VAV, fan-coil, heat-pump, and controls brands that already standardised on Modbus and need a branded room IAQ node. It is not written for installers buying a single sensor.

Alledio sells to OEMs only. The commercial model starts at MOQ 1,000 pcs, negotiable per programme, with sample devices for lab evaluation before production. There is no webshop; installers and integrators receive devices through the OEM brand that specifies them.

Write the protocol choice into the RFQ early. ANM is the Modbus-focused twin; ANB adds native BACnet MS/TP and BACnet/IP on the same sensing platform. Mixed estates that need both languages should open the BACnet wall multi-sensor guide instead of forcing a gateway onto a Modbus-only map.

What one Modbus multi sensor OEM node measures

The ANM line combines physical sensing and computed psychrometrics in a single wall housing. Which registers are populated depends on the variant you order, so the product code belongs in the specification, not in a later change request.

Measured values

Temperature (output range -40 °C to +125 °C, typical ±0.5 °C at 0–65 °C) and humidity (0–100 % RH, ±1.8 % RH at 30–70 %) are standard; ±0.2 °C and ±1 % RH are available on request. CO2 reads 0–5000 ppm at ±(50 ppm + 5 % of reading) between 400 and 2000 ppm, with automatic self-calibration every 7 days.

VOC is reported as a VOC Index from 1 to 500, where 100 is the learned 24-hour baseline of that room. Pressure covers 300–1200 hPa. Presence reports detected or not detected from about 1.0 m to 10.5 m. A THPM2.5 variant is listed on the product page, but PM2.5 is not yet in the current datasheet's variant or register table; ask for availability, register mapping, and accuracy data in the RFQ.

Computed values

Dew point, enthalpy, and density of moist air are calculated on the device from temperature, humidity, and pressure. That hands an AHU or VAV controller psychrometric inputs without extra PLC maths. The background is covered in our article on why enthalpy matters in AHUs.

The ANM family scales from a TH temperature and humidity node up to THPVCP, which adds pressure, VOC, CO2, and presence. When a sensing element is not fitted on a variant, its Modbus registers stay out of service rather than sending fake zeros to the trend log - document that behaviour in the ICD.

Commercial IAQ use cases on Modbus trunks

Offices and meeting rooms

Meeting rooms swing from empty to crowded in minutes. CO2 and presence together let the BMS run demand-controlled ventilation per room instead of a fixed schedule, while the VOC Index catches overnight cleaning and new-furniture off-gassing that CO2 alone misses.

Mount the node at about 1.5 m on an inside wall, away from direct supply-air blow, fan coils, and split units. Flush mounting fits a standard EU flush box (Ø 68 mm, 60 mm screw spacing, minimum 40 mm deep). The housing is rated IP30 for -10 °C to +50 °C and up to 85 % RH non-condensing.

VAV, AHU, and FCU zones

On VAV and AHU projects the same node feeds zone temperature and CO2 to the box controller and gives the air handler enthalpy and dew point for economiser and dehumidification logic. One device replaces separate temperature, humidity, and CO2 transmitters on the same wall.

The Multi-Sensor has no display. When occupants need a setpoint screen, add a separate wall UI such as the Room Unit or an OEM Room Controller with universal I/O, and keep the sensor where airflow is clean.

Retail, server rooms, and open offices

Retail floors, server rooms, and open offices use the same register map with different thresholds. Server rooms lean on temperature and humidity trends; retail and open-plan zones lean on CO2 and VOC. One SKU family keeps the BMS template identical across the portfolio.

Modbus RTU vs Modbus TCP wall nodes

ANM ships as a Modbus RS-485 (RTU) wall node on RS-485. That is the default copper path for most OEM HVAC controllers that already poll room sensors as slaves. Baud is selectable from 9600 to 115200 with optional 120 Ω termination; twisted pair with drain wire is the field standard.

Modbus RTU on the wall keeps wiring, addressing, and spare parts identical to the rest of your copper plant. Slave address, parity, and register map belong in the same ICD as the sensing variant. For Modbus RTU, plan on about 31 devices per segment as the typical recommendation, with more possible depending on cable quality and configuration; isolated RS-485 up to 1 kV is available on special request.

Modbus TCP on the wall is a different network design: it needs an Ethernet or Wi-Fi path to a TCP gateway or native TCP master, plus IT agreement on addressing and VLANs. Alledio's ANM focus for this article is the RS-485 RTU wall node. If your programme truly needs TCP end-to-end at the glass, document the gateway or IP path as a separate line item - do not assume the copper SKU speaks TCP without that pack.

Programmes that also require native BACnet objects should specify the ANB twin (covered in the OEM BACnet wall multi-sensor article) rather than inventing a dual-stack claim on ANM. For Modbus-only estates, ANM keeps one protocol, one spare SKU.

NFC commissioning and calibration

There are no DIP switches. Tap an Android or iOS phone on the case, and NFC opens a local web app in the browser over a hidden Wi-Fi link that works within about 2 m and switches off after 15 minutes.

From that app the commissioning engineer sets Modbus address and line parameters, and per-sensor offsets against a reference instrument. Firmware update and rollback run from the same menu.

After first power-up, allow 30–45 minutes of initial auto-calibration before setting offsets. For CO2, the room should see roughly 400–500 ppm at least once a week so the 7-day self-calibration stays accurate; put that in the O&M notes for 24/7 spaces.

Product proof and OEM branding

Published proof for a Modbus IAQ programme is the combination of RS-485 Modbus sensing, computed psychrometrics, and NFC setup in one EU-made wall node. The design was recognised with a Red Dot award in 2026.

Not claimed here: a BTL listing, a KNX SKU, native BACnet on ANM, installer webshop pricing, or Modbus TCP as the default wall copper SKU. Confirm every cell against the current datasheet and manual before you lock the RFQ.

OEM customisation covers logo, finish (bright white or blurred black), packaging, Modbus defaults, and firmware. For larger programmes Alledio can integrate further sensors such as lux, sound level, or formaldehyde, validated on your chosen protocol through OEM engineering.

The sensor was shown to HVAC and refrigeration buyers at Refrigera 2025 in Bologna. Compliance starts from RED 2014/53/EU, including Delegated Regulation (EU) 2022/30, and RoHS; ask for the EU Declaration of Conformity with the sample. More on about Alledio.

FAQ

Is this Modbus native or through a gateway?
Native Modbus RTU on RS-485 for the ANM line. No protocol gateway is required between the sensor and a Modbus master that already speaks RTU.

How is ANM different from ANB?
ANM is the Modbus-focused twin. ANB adds native BACnet MS/TP and BACnet/IP on the same sensing platform. Pick the code that matches the trunk you certify.

Can an installer buy one sensor from a webshop?
No. Alledio sells to OEMs. Installers and integrators get devices through the OEM brand that specifies them.

Does the sensor run the plant from the wall?
No. It is a sensing node. Control sequences, safeties, and setpoints stay in the BMS or your OEM controller, which reads the Modbus registers.

Is there a KNX SKU or a BTL listing?
No KNX catalogue SKU is published, and a BTL listing is not claimed. Ask for the current protocol documentation in the RFQ if your tender requires it.

What is the MOQ and can we get samples?
MOQ starts at 1,000 pcs and is negotiable. Samples ship with demo or test firmware so your lab can check addressing, registers, and offsets before production firmware and branding are locked.

Can we specify PM2.5?
A THPM2.5 variant is listed on the product page but is not yet in the current datasheet's variant or register table. Ask for availability, mapping, and accuracy data in the RFQ.

What to do next

Start on the Alledio OEM Multi-Sensor page, then open an OEM conversation for ANM variant code, finish, branding, Modbus defaults, and samples. Bring the zone list, RS-485 trunk plan, address range, and target volume. That is the shortest path from an RFQ line to a branded Modbus IAQ node on your customers' walls.