Therm-Outdoor-Air

Supported Applications

The ACI Thermistor Outside Air Series is a single-point outdoor temperature sensor designed for use with electronic controllers in commercial heating and cooling building-management systems. Each sensor uses a weatherproof enclosure with a water-tight cord-grip fitting, and the sensing element is built with ACI's double-encapsulation process to eliminate the effects of moisture ingress, making it well suited to permanent outdoor mounting.

The series is offered with a wide choice of thermistor curves so it can be matched to nearly any controller input, and with several enclosure styles for different mounting and environmental needs. Correct siting is important: mount the sensor out of direct sunlight on the north side of a building, in shade, below the eave and above the ground, and away from chimney walls, windows, vents, doors, and dampers so that thermal radiation does not affect the reading. Signal wiring must be kept separate from low- and high-voltage wiring and must not share conduit with line voltage (24/120/230 VAC).

Operating Conditions & Performance

The sensor operates over -40 to 70°C (-22 to 158°F), with the same range applying to storage. Accuracy across 0-70°C (32-158°F) is ±0.2°C (±0.36°F) for most series, ±0.3°C (±0.54°F) for the A/10K-E1 series, and ±0.5°C @ 25°C (77°F) for the A/1.8K series, which is also specified at (±1.0°C) (±1.8°F). The sensor is a non-linear NTC thermistor with a single sensing point and a nominal response time of 25 seconds (63% step change).

Operating humidity is 10 to 95% RH, non-condensing. The element terminates in two non-polarity-sensitive 14” (35.6 cm) 22 AWG (0.65 mm) etched Teflon (PTFE) colored leads, whose colors identify the sensor type. The sensors are CE marked and RoHS2 compliant.

Three enclosure styles are available. The “-EH” Euro enclosure is ABS/PC-ASA plastic with a UV protectant, rated UL94-V0. The “-4X” enclosure is polystyrene plastic, rated UL94-V2 and IP66 (NEMA 4X). The “-BB” Bell Box enclosure is aluminum, rated IP32 (NEMA 3R). Representative widths are 4.00” (101.57 mm) for the Euro enclosure, 2.55” (64.77 mm) for the NEMA 4X enclosure, and 2.95” (75 mm) for the Bell Box.

Configuration Options

Every model follows the pattern A/ - Sensor Series - Configuration - NIST (for example, A/CP-O-EH), so a code selects three independent capabilities:

• Sensor series (nominal resistance @ 25°C): A/1.8K is 1.8 KΩ, A/3K is 3 KΩ, A/AN (Type III) is 10 KΩ, A/AN-BC is 5.238 KΩ, A/CP (Type II) is 10 KΩ, A/CSI is 10 KΩ, A/10KS is 10 KΩ, A/10K-E1 is 10 KΩ, A/20K is 20 KΩ, A/50K is 50 KΩ, and A/100KS is 100 KΩ. The lead-wire color pair differs for each series to make them easy to tell apart.
• Configuration (enclosure): O-EH selects the Euro housing, O-BB selects the aluminum Bell Box, and O-4X selects the NEMA 4X enclosure, which sets the enclosure material and NEMA/IP rating as described above.
• NIST: models can be ordered with or without a NIST calibration certificate; the -NIST suffix adds the certificate.

Because accuracy, power-dissipation constant, and lead-wire colors are tied to the sensor series, selecting the series sets both the electrical characteristic the controller expects and the sensor's specified accuracy grade.

Key Product Differences

The series is offered in the following configured models:

• A/1.8K-O-4X, A/1.8K-O-BB, A/1.8K-O-EH
• A/3K-O-4X, A/3K-O-BB, A/3K-O-EH, A/3K-O-EH-NIST
• A/10KS-O-4X, A/10KS-O-BB, A/10KS-O-EH
• A/10K-E1-O-4X, A/10K-E1-O-BB, A/10K-E1-O-EH, A/10K-E1-O-EH-NIST
• A/20K-O-4X, A/20K-O-BB, A/20K-O-EH
• A/50K-O, A/50K-O-4X, A/50K-O-BB
• A/100KS-O-4X, A/100KS-O-BB, A/100KS-O-EH
• A/AN-BC-O-4X, A/AN-BC-O-BB, A/AN-BC-O-EH, A/AN-O-EH-NIST
• A/CP-O-4X, A/CP-O-4X-NIST, A/CP-O-BB, A/CP-O-EH, A/CP-O-EH-NIST
• A/CSI-O-4X, A/CSI-O-BB, A/CSI-O-EH

NIST-certified variants add a NIST calibration certificate to the corresponding base model.