Duct Temperature Sensor NTC 20K (Passive)

Passive NTC 20K sensor for measuring supply, return and fresh air temperature in air ducts and air handling units. Combined with an EPL-SS stainless steel sensor well it can also be used as an immersion sensor on pipework. Connects directly to the NTC 20K inputs of DDC, PLC and fan-coil controllers. KEY FEATURES • TDK (EPCOS) NTC 20 kΩ element, R25 tolerance ±1 % (≈ ±0.2 K at 25 °C) • Ø6 mm stainless steel probe, epoxy filled • ABS housing with PG7 cable gland, screw terminals (0.5 … 2.5 mm²), IP67 • Quick mounting on the duct wall with 2 screws; a rubber seal closes the hole airtight • Passive, 2-wire, non-polarised: no power supply needed PROBE LENGTH OPTIONS • 100 mm — matching well EPL-SS-100 • 150 mm — matching well EPL-SS-150 Please state the probe length when ordering. Choose the 150 mm probe for wide ducts. TECHNICAL SPECIFICATIONS Sensing element: NTC thermistor, epoxy-coated disc (TDK EPCOS) Resistance: R25 = 20 kΩ · B25/100 = 4300 K (R/T curve 2904) Tolerance: R25 ±1 % → ≈ ±0.2 K @ 25 °C Operating temperature: −30 … +80 °C (element −55 … +155 °C) Measuring current: ≤ 0.1 mA (recommended) Self-heating: ≈ 4 mW/K (element) → ≈ 0.05 K at 0.1 mA Output: Passive resistance, 2-wire, non-polarised Connection: 2-pole screw terminal, 5.0 mm, PA66 UL 94 V-0 Wire size / strip length: 0.5 … 2.5 mm² / 8 mm · tightening torque 0.5 N·m Cable gland: PG7 Probe: Stainless steel, Ø 6 mm, epoxy filled Probe length: 100 / 150 mm Housing: ABS Mounting: 2 screws on the duct surface Weight (ready to install): 67 g Degree of protection: IP67 (EN 60529) Environment: Non-condensing Protection class: III — safety extra-low voltage (SELV/PELV) circuits only Element approval: UL (E69802) Conformity: CE · WEEE 2012/19/EU (not household waste) RESISTANCE VALUES (EXAMPLES) 0 °C: 71,126 Ω · 25 °C: 20,000 Ω · 50 °C: 6,673 Ω · 70 °C: 3,061 Ω Thanks to the high resistance of NTC 20K, cable resistance has very little effect: even on a 100 m run of 2 × 0.5 mm² the error is only −0.01 K at 25 °C, so no offset correction is normally needed. WIRING AND INSTALLATION • On the controller, set the NTC 20K input to the B25/100 = 4300 K curve. The common "NTC 20K B3950" curve is different; selecting it can shift the reading by 1.5–2 °C. • Drill a hole in the duct wall sized for the rubber seal; the probe tip should sit in the middle third of the duct cross-section. • Fix the housing to the duct with 2 screws, with the PG7 gland facing down. Strip the wires 8 mm, connect them to the terminal (0.5 N·m) and tighten the gland to seal the cable entry. • Do not mount directly downstream of heating or cooling coils or humidifiers; choose a point where the air is fully mixed. • For pipework (water) applications, use it together with an EPL-SS well of the matching length. • Connect the sensor only to the low-voltage sensor input of a controller; never connect it to 230 V mains. Wiring must be done by qualified personnel with the power off; do not run the sensor cable in the same duct or conduit as 230 V power cables. SCOPE OF DELIVERY 1 × sensor, 2 × mounting screws and wall plugs