Nickel-Immersion

Supported Applications

The ACI Nickel Immersion Series is a single-point Nickel RTD temperature sensor for use with electronic controllers in commercial heating and cooling building-management systems. It uses a ¼" diameter stainless-steel probe with two 22 AWG etched-Teflon colored lead wires, and installs into a ½" NPS female thread — typically through a Threadolet or Tee, or into a thermowell.

Because it reads temperature directly in the flowing medium, the series suits air, gas, steam and water piping. ACI's double-encapsulation process and thermally conductive epoxy protect the element from moisture and speed thermal response. For accurate readings the thermowell tip should sit in the middle of the pipe and be installed against the flow where the medium is well mixed, and thermal grease should be applied to the probe before insertion into a thermowell.

Operating Conditions & Performance

The sensor is a Nickel RTD with a positive-temperature-coefficient (PTC) curve, a nominal output of 1000 Ohms at 21.1°C and Red/Red leads. It conforms to DIN 43760 with a temperature coefficient of 6370 ppm/°C and operates over -40 to 121°C.

Accuracy is ±1.52°C at -40°C, ±0.4°C at 0°C, ±0.17°C at 21.1°C, ±0.56°C at 54.4°C and ±1.25°C at 121°C. Response time is 8 Seconds nominal, self-heating is 0.3°C/mW in still air, the maximum operating current is 5 mA, and long-term stability is ±0.05% after 1000 Hours at 150°C.

The probe is 304 stainless steel with a 6.35 mm diameter and 22 AWG (0.65 mm) wire. When used with a two-part fabricated/welded thermowell, the 304/316 SS assembly is pressure-rated from 982 PSI (67.7 Bar) at 70°F (21.1°C) down to 290 PSI (20.0 Bar) at 1200°F (648.9°C). Storage is rated -40 to 85°C, humidity 10 to 95% RH non-condensing, and the series is CE, RoHS2 and WEEE compliant.

Configuration Options

All variants share the Nickel RTD element and accuracy; they differ by insertion length, configuration and enclosure:

• Insertion length — probes are offered from 1" up to 24", with standard immersion lengths such as 2.5" (63.50 mm), 4.0" (101.60 mm) and 6.25" (158.75 mm) reaching the middle of pipes of different diameters.
• Configuration — the I, IM and INW configuration codes cover direct-immersion and thermowell-mounted arrangements.
• -GD Galvanized — galvanized steel, -40 to 121°C, NEMA 1 (IP10).
• -PB Plastic box — ABS plastic, UL94-HB, -30 to 90°C, plenum rated.
• -BB Bell box — aluminum, -40 to 121°C, NEMA 3R (IP 14).
• -4X enclosure — polystyrene plastic, UL94-V2, -40 to 70°C, NEMA 4X (IP 66).

Enclosure choice also sets the housing size; the plastic box (-PB) measures 91.44 mm x 121.55 mm x 59.80 mm, while the galvanized enclosure (-GD) measures 58.67 mm x 106.17 mm x 43.37 mm.

Key Product Differences

Models follow the scheme A/1K-NI-<configuration>-<insertion length>-<enclosure>, for example A/1K-NI-IM-4"-4X-NIST. Representative variants include:

• A/1K-NI-I-2.5"-GD, A/1K-NI-I-4"-PB and A/1K-NI-I-6"-4X — direct-immersion (I) variants.
• A/1K-NI-IM-2.5"-BB, A/1K-NI-IM-4"-GD and A/1K-NI-IM-6"-PB — IM-configuration variants.
• A/1K-NI-INW-2.5"-4X, A/1K-NI-INW-12"-GD and A/1K-NI-INW-18"-PB — INW-configuration variants spanning the longest 12" and 18" insertions.

Each combination can be ordered with or without a NIST Certificate, letting the sensor be matched to the pipe size, mounting method, enclosure environment and traceability required.