Transmitter-Immersion

Supported Applications

The ACI Immersion Series is a family of single-point immersion temperature sensors and transmitters for commercial heating and cooling building management systems. Each unit is designed to read the temperature of a fluid or gas inside a pipe, tank or duct and report it to an electronic controller or building automation system (BAS). The wetted probe is 304 Stainless Steel, and units are offered for Air/Gas/Steam and Water media.

Installation is into a ½" NPT (National Pipe Tapered) male thread or ½" NPS (National Pipe Straight) female thread, typically through a Threadolet or Tee, and a machined thermowell option isolates the sensor from the process. Thermal grease (ACI Item #102595) is applied to the probe tip before insertion into a thermowell. The "INW" version can be ordered without the thermowell where higher corrosion resistance is required. ACI advises that wiring never share a conduit with line voltage (24/120/230 VAC).

Operating Conditions & Performance

Transmitter models output 4-20 mA (2-Wire) with an optional voltage output of 1-5 VDC or 2-10 VDC (3-Wires), and are powered from an unregulated or regulated 8.5 to 32 VDC supply (reverse-polarity protected). Maximum load resistance depends on supply voltage: a 250 Ω load needs +13.5 to 32 VDC and a 500 Ω load needs +18.5 to 32 VDC. Transmitter response time is 8 Seconds nominal.

The platinum RTD element is a positive temperature coefficient (PTC) type with a single sensing point conforming to DIN EN 60751 (IEC 751), offering 100 Ω nominal (A/TT100, A/TTM100) or 1 KΩ nominal (A/TT1K, A/TTM1K) output referenced at 0°C (32°F), with a tolerance of ±0.06% Class A. The probe is 0.250" (6.35mm) 304 Stainless Steel. The unit operates over an ambient range of -40 to 85 °C (-40 to 185 °F), stores at -40 to 85 °C (-40 to 185 °F), and tolerates 0 to 90% RH non-condensing humidity.

Immersion length options are 2.5" (63.50 mm), 4.0" (101.60 mm) and 6.25" (158.75 mm), corresponding to overall probe lengths of 4.31" (109.47 mm), 5.81" (147.57 mm) and 7.81" (198.37 mm). Welded-thermowell pressure ratings for 304/316 SS run from 982 PSI (67.7 Bar) at 70°F down to 290 PSI (20.0 Bar) at 1200°F, while the high-temperature configuration is rated to a maximum of 2900 PSI at 1000°F (537.8°C) for Air/Gas/Steam and 5700 PSI for Water.

Configuration Options

The Immersion family covers both RTD and thermistor sensing. Beyond the platinum RTD elements, thermistor options include A/1.8K (1.8 KΩ nominal), A/3K (3 KΩ nominal), A/10K and A/CSI (10 KΩ nominal), A/20K (20 KΩ nominal), A/50K (50 KΩ nominal) and A/AN-BC (5.238 KΩ nominal), each identified by a distinct lead-wire color pair. Thermistor accuracies vary by type, for example ±0.2 °C (+/-0.36 °F) on the tighter grades.

Sensor construction distinguishes the standard immersion probe from the "INW" no-thermowell build and from the high-temperature series, which uses a three-wire assembly with Nickel Fiberglass lead wires and a 316 Series stainless steel probe in a machined 304 SS thermowell. The high-temperature transmitter carries a calibrated accuracy of +/- 0.2% for temperature spans under 500°F (260°C) and +/- 0.5% for spans over 500°F (260°C).

Enclosure choice determines rating and material: the Galvanized Steel -GD is NEMA 1 (IP10) rated for -40 to 121 °C (-40 to 250 °F); the ABS Plastic -PB is UL94-HB plenum rated for -30 to 90 °C (-22 to 194 °F); the Aluminum bell-box -BB is NEMA 3R (IP 14); and the Polystyrene -4X is UL94-V2, NEMA 4X (IP 66), rated for -40 to 70°C (-40 to 158°F).

Key Product Differences

Standard part numbers follow the pattern A/xx-I-<LENGTH>-yy-zz, while the no-thermowell build uses A/TTxx-INW-<length>-yy-zz. Every part is assembled from sensor series, immersion length, output/wiring and enclosure.

• Sensor type: platinum RTD (TT100 = 100 Ω, TT1K = 1 KΩ, plus matched TTM100 / TTM1K) or thermistor (A/1.8K, A/3K, A/10K, A/20K, A/50K and related curves).
• Immersion length: 2.5" (63.50 mm), 4.0" (101.60 mm) or 6.25" (158.75 mm).
• Output / wiring: 4-20 mA (2-Wire) current or 1-5 VDC or 2-10 VDC (3-Wires) voltage for transmitters; two- or three-wire flying leads for bare sensors.
• Enclosure: Galvanized Steel (-GD), ABS Plastic (-PB), Aluminum bell box (-BB) or Polystyrene NEMA 4X (-4X).

Representative catalog part numbers include A/TT100-I-2.5"-1-4X, A/TT100-IM-4"-4-GD and A/TT100-INW-2.5"-2-BB. The high-temperature line adds high-temp, configuration, thermowell insertion length and NIST fields, following the pattern A/1K-3W-HT-IM-4"-GD-NIST.