Therm-Strap-On

Supported Applications

The ACI Thermistor Strap-On Series is a single point temperature sensor designed for use with electronic controllers in commercial heating and HVAC systems. It features a 1.5" square copper plate with the sensor encapsulated to the back side of the plate to improve the thermal conductivity between the pipe and the sensor. This makes the series the preferred choice when an immersion style sensor cannot be inserted into the pipe.

The strap-on clamp mounting adapts to a wide range of line sizes. The S configuration fits a 1.25" to 4" pipe size, while the S10 configuration fits a 2" to 10" pipe size. For the best thermal contact, clean the pipe with an emery cloth or file, apply thermal grease between the sensor plate and the pipe, and insulate the sensor from the effects of ambient air.

Each sensor terminates in two non-polarity sensitive lead wires, supplied as 14 inch Etched Teflon colored leads so the different sensor types can be differentiated. Do not run the wiring in any conduit with line voltage (24/120/230 VAC). When using a shielded cable, connect only one end of the shield to ground at the controller.

Operating Conditions & Performance

Sensor accuracy is specified across a 0 to 70 °C (32 to 158 °F) range. The response time is 30 Seconds nominal, and the operating humidity range is 10 to 95% RH, non-condensing. The wiring accepts 14 to 22 AWG twisted pair wires or shielded cable, with a nominal wire size of 22 AWG (0.65 mm). The series carries CE, RoHS2 and WEEE compliance.

The usable operating temperature is governed by the selected enclosure:

• Galvanized Steel (GD): -40 to 93 °C (-40 to 200 °F), rated NEMA 1 (IP 10).
• ABS Plastic (PB): -30 to 85 °C (-22 to 185 °F), UL94-HB, Plenum Rated.
• Polystyrene (4X): -40 to 70 °C (-40 to 158 °F), UL94-V2, NEMA 4X (IP 66).

The specified storage temperature range is -40 to 80 °C (-40 to 176 °F).

Configuration Options

The sensor series differ primarily by their nominal output resistance at 25 °C (77 °F), each identified by a distinct lead wire color pair:

• 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)

Accuracy also varies by series. Most sensors are rated to ±0.2 °C (±0.36 °F), while the A/10K-E1 Series is rated to ±0.3 °C (±0.54 °F) and the A/1.8K Series is rated to ±0.5 °C at 25 °C (77 °F). All thermistors use a Non-Linear, NTC (Negative Temperature Coefficient) curve with one sensing point and two non-polarity sensitive wires.

The enclosure choice determines the environmental protection: GD galvanized steel provides a NEMA 1 (IP 10) housing, PB plastic is plenum rated, and 4X delivers a NEMA 4X (IP 66) weather proof enclosure. A NIST option adds a 3 point calibration certificate.

Key Product Differences

Models follow the structure A/<SENSOR SERIES>-<CONFIGURATION>-<ENCLOSURE>-<NIST>, for example A/1.8K-S-PB-NIST. Each position is selected independently:

• Sensor Series: 1.8K, 3K, AN, AN-BC, CP, CSI, 10KS, 10K-E1, 20K, 50K or 100KS.
• Configuration: S = Strap-On (1.25" to 4" Pipe Size) or S10 = Strap-On (2" to 10" pipe size).
• Enclosure: GD = Galvanized, PB = Plastic or 4X = NEMA 4X Weather Proof.
• NIST: no certificate, or NIST = NIST Certificate (3 Points).

Representative catalog numbers include A/1.8K-S-GD, A/10K-E1-S-PB, A/AN-S10-4X, A/100KS-S-PB and A/CP-S10-PB-NIST. Compatible accessories are the A/HOSE CLAMP-2-5" (Item #142630) and A/HOSE CLAMP-2-12" (Item #142631) quick release worm gear stainless steel clamps, plus NSG HEAT TRANSFER PASTE 2OZ (Item #102595) and NSG HEAT TRANSFER PASTE 16OZ (Item #140574) silicone free thermal grease.