Duct Mounting Humidity Temperature Monitor

Description

The duct mounting humidity and temperature transmitter (AI-RHTx-D) is suited for mounting in HVAC ducts in a rugged IP65-rated plastic enclosure with an adjustable duct clamp. The instrument features a polymer capacitive sensor that reliably measures temperature and humidity with high accuracy. The capacitive basic sensor is not affected by condensation & gives top-of-the-line long-term stability. The AI-RHTx-D is a high accuracy solution with customizable measuring ranges. The duct transmitter provides dual 4-20mA outputs, 1 each for humidity and temperature.

Applications include humi-temp monitoring in offices, retail spaces, educational institutions, industries in HVAC systems and is well suited with 4-20mA output for the monitoring of smart buildings and smart industrial applications.

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AHU Supply Air Monitoring

Positioned in the supply ductwork downstream of an air handling unit, the monitor verifies that the AHU is delivering correctly conditioned air against design supply temperature and humidity setpoints. This confirms the AHU is performing as intended before conditioned air reaches occupied spaces, supporting supply air quality expectations referenced in ASHRAE 62.1, and giving facility teams an early indicator if cooling, heating, or humidification isn't tracking to setpoint.

Return Air Monitoring

Installed in the return duct, the monitor measures the temperature and humidity of air being drawn back from occupied spaces before it re-enters the AHU. Understanding what conditions buildings are exhausting helps facility teams optimise AHU operation, informing decisions on mixed air ratios, economiser operation, and overall system efficiency based on actual building conditions rather than supply-side assumptions alone.

HVAC Humidification Control

In systems with active humidification, the monitor's duct RH measurement can directly control humidifier output, maintaining supply air humidity at the design setpoint. As duct RH drifts below target, the humidifier increases output; as it approaches setpoint, output tapers accordingly. This closed-loop approach keeps supply air humidity stable regardless of changing outdoor conditions or building load.

Features

• Polymer capacitive sensing for humidity and temperature measurement
• Durable ABS duct mounting plastic enclosure
• No effect of condensation on output & stability
• Optional display

Applications

• AHU Supply Air Monitoring: Verifies conditioned air leaving the AHU meets design temperature and humidity setpoints before reaching occupied zones
• Return Air Monitoring: Measures conditions being exhausted from occupied spaces, informing AHU mixed air and economiser operation
• Humidification Control: Drives humidifier output based on real-time duct RH measurement, maintaining supply air humidity at setpoint
• Multi-Zone Commercial HVAC: Supports verification across AHUs serving multiple zones with varying supply air requirements
• HVAC Commissioning and Diagnostics: Provides direct duct-level T/RH data useful for verifying system performance during commissioning or troubleshooting

Installation Guide

The probe is inserted through the duct wall at a point in the airstream that avoids turbulence from nearby fans, elbows, or branch takeoffs, ensuring the sensor captures a representative reading of the conditioned air. Insertion depth should be sized to the duct's dimensions so the sensing tip sits within the main airflow rather than near the duct wall boundary layer, where temperature and humidity readings can be less representative of the bulk airstream.

Frequently Asked Questions (FAQs)

1. What is the AI-RHTx-D Duct Mounting Temperature Humidity Monitor?

The AI-RHTx-D is a duct-mounted temperature and humidity monitor designed to continuously measure the temperature and relative humidity of air flowing through HVAC ducts. It provides real-time environmental data to Building Management Systems (BMS), PLCs, and HVAC controllers, helping optimize indoor air quality, occupant comfort, and HVAC energy efficiency.

2. What does the AI-RHTx-D measure?

The monitor continuously measures:

• Temperature
• Relative Humidity (RH)

These measurements help monitor the performance of HVAC systems and maintain the desired indoor environmental conditions.

3. Why is temperature and humidity monitoring needed in HVAC ductwork?

The Air Handling Unit (AHU) is responsible for heating, cooling, humidifying, or dehumidifying supply air before it is distributed throughout the building.

By continuously monitoring the temperature and humidity of the supply air, the AI-RHTx-D verifies that the AHU is delivering air at the required design conditions. If the supply air becomes too warm, too cold, too humid, or too dry, the Building Management System can automatically adjust the AHU operation to restore the desired setpoints.

Monitoring return air also provides valuable information about actual building conditions and identifies opportunities for energy recovery and HVAC optimization.

4. Where should the duct temperature and humidity sensor be installed?

For accurate measurements, the sensing probe should be installed in a straight section of ductwork where airflow is well mixed.

Recommended installation locations include:

• At least 10 duct diameters downstream from bends, dampers, diffusers, or other airflow disturbances.
• In the main supply air duct after the Air Handling Unit (AHU) outlet damper for supply air monitoring.
• In the main return air duct before the AHU for return air monitoring.

Correct installation ensures representative temperature and humidity measurements.

5. Where is the AI-RHTx-D commonly installed?

Typical applications include:

• Air Handling Units (AHUs)
• Supply air ducts
• Return air ducts
• Commercial buildings
• Hospitals
• Pharmaceutical manufacturing facilities
• Cleanrooms
• Laboratories
• Data centers
• Hotels
• Shopping malls
• Educational institutions
• Industrial HVAC systems

6. Can this sensor control a humidifier?

Yes. The AI-RHTx-D communicates with the Building Management System through RS485 Modbus.

The BMS compares the measured duct humidity with the desired humidity setpoint and automatically adjusts the humidifier output to maintain the required supply air humidity. This closed-loop control ensures stable humidity levels despite changes in outdoor weather or building occupancy.

7. What accuracy can I expect from the temperature and humidity sensors?

The AI-RHTx-D uses high-quality factory-calibrated sensors.

Typical performance is:

• Relative Humidity Accuracy: ±3% RH (within the 10-90% RH range)
• Temperature Accuracy: ±0.3°C

Both sensors are calibrated against traceable standards to ensure reliable and repeatable measurements.

8. Can the AI-RHTx-D be integrated with a Building Management System (BMS)?

Yes. The monitor supports industry-standard communication options, including:

• RS485 Modbus communication
• 4 - 20 mA output
• 0 - 10 V output (depending on model)

These outputs allow seamless integration with Building Management Systems, PLCs, SCADA systems, and HVAC automation controllers.

9. Can the AI-RHTx-D improve HVAC energy efficiency?

Yes. Continuous monitoring of supply and return air temperature and humidity allows the Building Management System to optimize heating, cooling, humidification, and dehumidification based on actual operating conditions. This reduces unnecessary energy consumption while maintaining occupant comfort.

10. Is the AI-RHTx-D suitable for continuous monitoring?

Yes. The AI-RHTx-D is designed for reliable 24×7 continuous operation in commercial, industrial, healthcare, pharmaceutical, and institutional HVAC applications.

11. Does the monitor require calibration?

The AI-RHTx-D is factory calibrated before shipment to ensure accurate measurements. Periodic verification is recommended for applications requiring high measurement accuracy, particularly in pharmaceutical manufacturing, cleanrooms, laboratories, and regulated environments.

12. Is installation easy?

Yes. The duct-mounted probe is designed for straightforward installation through the duct wall using standard mounting hardware, making it suitable for both new HVAC systems and retrofit projects.

13. What are the advantages of using the AI-RHTx-D?

Key benefits include:

• Continuous temperature and humidity monitoring
• Accurate supply and return air measurement
• Improved HVAC performance
• Supports humidifier and dehumidifier control
• Better indoor air quality
• Improved energy efficiency
• Easy BMS and PLC integration
• Reliable industrial-grade performance

14. Who typically uses the AI-RHTx-D?

The AI-RHTx-D is widely used by:

• HVAC contractors
• Building automation integrators
• Facility managers
• Hospital engineering teams
• Pharmaceutical manufacturers
• Cleanroom consultants
• Laboratory managers
• Data center operators
• Industrial maintenance engineers

15. Why choose ACE Instruments?

ACE Instruments has over 30 years of experience in manufacturing HVAC and environmental monitoring solutions. Customers choose our products for their high measurement accuracy, industrial-grade reliability, easy BMS integration, multiple communication options, calibration support, responsive technical assistance, and proven performance across commercial, healthcare, pharmaceutical, and industrial facilities.

16. How do I choose the right Duct Mounting Temperature Humidity Monitor?

Selecting the right AI-RHTx-D depends on your HVAC application, duct size, communication requirements, output signal, installation location, and environmental conditions.

Our application engineers can help you select the most suitable AI-RHTx-D configuration for supply air monitoring, return air monitoring, cleanrooms, pharmaceutical facilities, commercial buildings, or any HVAC application requiring accurate duct temperature and humidity measurement.

Specifications