Therm-Duct-No-box

Supported Applications

The ACI Thermistor Duct No Box Series consists of single-point temperature sensors designed for use with electronic controllers in commercial heating and cooling building management systems. These duct style sensors are intended for installation within air handling ducts to monitor process temperatures.

Sensors feature a double encapsulation process using high-quality, thermally conductive epoxy to eliminate the effects of moisture on sensor performance. The series includes an insulation pad designed to seal the mounting hole in the duct and dampen vibration during operation.

Operating Conditions & Performance

The series supports a measurement range from -40 to 115°C (-40 to 239°F) for thermistor elements, with an operating ambient temperature of -40 to 85°C (-40 to 185°F). Storage temperatures are rated up to -40 to 115°C (-40 to 239°F), while the plastic box enclosure variant is limited to a storage range of -30 to 90°C (-22 to 194°F).

• Response time: 10 Seconds nominal (63% step change)
• Humidity rating: 10 to 95% RH, non-condensing
• Power dissipation constant: 3 mW/°C for most series; 1 mW/°C for A/1.8K Series; 2 mW/°C for A/10K-E1 Series

Accuracy varies by sensor element type:

• A/1.8K Series: +/- 0.5°C @ 25°C (77°F) and (+/-1.0°C) (+/-1.8°F)
• A/10K-E1 Series: +/- 0.3°C (+/- 0.54°F)
• All other thermistors: +/- 0.2°C (+/- 0.36°F) at 0-70°C (32 - 158°F)

For Platinum RTD options, accuracy is Class A with a tolerance formula of +/- °C = (0.15 °C + 0.002 * |t|). BALCO sensors offer +/- 1% at 21.1°C (70°F), while Nickel sensors range from +/- 0.17°C (+/- 0.34°F) to +/- 1.52°C (+/- 2.73°F) depending on temperature.

Configuration Options

The series is configurable across multiple sensor elements, probe lengths, and lead wire options to accommodate specific duct dimensions and controller requirements.

Sensor Elements & Output Signals

• A/1.8K: 1.8 KΩ nominal (Red/Yellow)
• A/3K: 3 KΩ nominal (White/Brown)
• A/AN (Type III): 10 KΩ nominal (White/White)
• A/AN-BC: 5.238 KΩ nominal (White/Yellow)
• A/CP (Type II): 10 KΩ nominal (White/Green)
• A/CSI: 10 KΩ nominal (Green/Yellow)
• A/10KS: 10 KΩ nominal (White/Blue)
• A/10K-E1: 10 KΩ nominal (Gray/Orange)
• A/20K: 20 KΩ nominal (Brown/Blue)
• A/50K: 50 KΩ nominal (Brown/Yellow)
• A/100KS: 100 KΩ nominal (Black/Yellow)

Probe & Mounting Options

Sensors feature a 0.250" (6.35 mm) diameter probe constructed of 304 Stainless Steel with a Galvanized Steel flange for duct mounting via a 3/8" hole. Available insertion lengths include 4", 6", 8", 12", and 18".

Lead Wire Configurations

• Standard: Etched Teflon (PTFE) Colored Leads, MIL-W-16878/4 (Type E), rated -55°C (-67°F) to 200°C (392°F)
• Plenum Rated CL2P: FEP insulation, suitable for indoor and outdoor wet locations; oil, gas, sunlight, abrasion, and acid resistant
• Plenum Rated CMP: Low Smoke PVC, UL Listed C(UL)US CMP, rated 0°C (32°F) to 75°C (167°F); suitable for indoor use only
• Cable lengths available in standard configurations or extended options including 6', 10', and 20' plenum cables.

Approvals & Certifications

The series carries UKCA, CE, RoHS2, and WEEE approvals. Optional NIST certificates are available for specific configurations requiring traceable calibration data (must specify 3 points).

Key Product Differences

Variants within the Therm-Duct-No-box series differ primarily by sensor resistance curve, probe insertion length, and lead wire insulation type.

• Sensor Series: Distinct model codes define the nominal resistance at 25°C (77°F) or specific temperature points for Platinum, BALCO, and Nickel elements. Lead wire colors correspond to each series code.
• Probe Length: Selection of 4", 6", 8", 12", or 18" insertion lengths allows the probe tip to reach the approximate center of ducts with varying widths or diameters.
• Cable Options: Standard PTFE leads are suitable for general indoor/outdoor wet locations. CL2P cables offer enhanced resistance to oil, gas, and UV exposure, while CMP cables provide low smoke characteristics but are restricted to indoor applications without UV light exposure.

Installation notes specify that the sensor should be placed 3 to 4 duct segments down from bends or obstructions. Mounting on the top or sides of duct work is required; mounting on the bottom risks damage due to moisture accumulation.