Belimo 22UTH-550X : Active Outdoor Humidity + Temperature Sensor with Radiated Heat Shield, Modbus RTU RH, Active Temp Output, NFC Config, Modbus RTU, 24 VAC/VDC, 5-Yr Warranty

What does the 22UTH-550X measure and output?

It measures outdoor air humidity and temperature and outputs both as analog signals. The humidity output is Modbus RTU (RS-485) with 0–10V analog backup outputs; the temperature output is an active analog signal matching the humidity output type. The humidity channel is also configurable via NFC to output absolute humidity, dew point, or enthalpy instead of %RH.

How do I configure the humidity output mode?

Tap an NFC-equipped phone with the Belimo Duct Sensor Assistant App against the housing. The app reads the current configuration, lets you switch the humidity output between %RH, absolute humidity, dew point, or enthalpy, and writes the new configuration back to the sensor — all without removing the sensor or disconnecting wires. Default is %RH. The app is free for iOS and Android.

Why does this SKU have an active temperature output instead of a passive RTD?

This variant ships with both outputs as ACTIVE analog signals — the temperature output matches the humidity output type (Modbus RTU). For a PASSIVE RTD temperature output (Pt 1000, Ni 1000 JCI, NTC 10K Type II, NTC 10K Type III, or NTC 20K) instead, choose the appropriate suffix variant — e.g. 22UTH-510B (Pt 1000), 22UTH-510L (NTC 10K II). Active outputs are simpler to wire (two signal pairs); passive RTDs are necessary when your controller's temperature input is wired for a specific resistance curve.

Does the Modbus RTU version still expose analog outputs?

Yes. The Modbus RTU version exposes all sensor values as bus objects AND maintains 2× 0-10V analog backup outputs (humidity + temperature). You can wire the analog outputs as a redundant feed, leave them unconnected, or use them to drive non-bus equipment (e.g. an analog damper actuator) while the BAS reads the bus values. This is useful for migration scenarios where the BAS is bus-native but field equipment is still analog.

How do I configure the Modbus RTU address and baud rate?

Use the Belimo Duct Sensor Assistant App via NFC. The app exposes all communication parameters — address, baud rate, parity (Modbus), MAC address (BACnet), device instance (BACnet) — and writes them to the sensor without taking it offline. For Modbus, the address is also writable via Modbus register 0x5401 once initial discovery is complete.

Why does this variant have a radiated heat shield?

The radiated heat shield is a curved white plate that protects the sensor elements from rain AND from radiated heat off rooftops, south-facing walls, and reflective surfaces. Without a shield, an outdoor sensor mounted near a black asphalt roof or a south-facing wall can read 5-15°F higher than true ambient on summer afternoons. The radiated shield variants are essential for any rooftop or sun-exposed install. For shaded or north-facing mount locations, the basic-shield variants (22UTH-51 or 22UTH-53) are sufficient.

What is the difference between humidity, dewpoint, and enthalpy as control inputs?

Relative humidity (%RH) tells you how saturated the air is at its current temperature — the most common input for indoor humidity control and dehumidification. Absolute humidity (g/m³) gives the total moisture content regardless of temperature — useful for mass-balance ventilation calculations. Dewpoint tells you the temperature at which moisture will start condensing — ideal for chilled-surface condensation prevention. Enthalpy (kJ/kg) is the total energy content of the air (sensible + latent) — the preferred input for ASHRAE-compliant economizer changeover, where the comparison should be energy-based rather than dry-bulb-temperature-based. Configure the output to match your control sequence.

Does it need 24V power?

Yes. Power is 24 VAC or 24 VDC. Power consumption is 4.3 VA AC / 2.3 W DC (higher than analog-only variants due to the active bus interface).