Products catalog

Home/Product Catalog/HVAC control solutions for heating and ventilation/HVAC automation/Sensors and detectors/Temperature sensors and thermostats
  • New item   Duct temperature sensor | NTC 1.8 kΩ | passive resistive | for air ducts

    Duct temperature sensor | NTC 1.8 kΩ | passive resistive | for air ducts

    Code: NTC 1.8 kOm
    Inquire about this item
    Price 24.20 € VAT incl.
    ( 20.00 € VAT excl. )
    Want another price? Suggest yours!

    The duct NTC 1.8 kΩ temperature sensor measures air temperature in a ventilation duct and passes it to the controller as a change in resistance. It suits only controllers whose input is configured for an NTC 1.8 kΩ sensor.

  • Product description

    Duct temperature sensor NTC 1.8 kΩ for air ducts

    The NTC 1.8 kΩ duct temperature sensor measures air temperature in ventilation and air conditioning ducts. The probe is inserted into the duct, and the NTC thermistor inside changes its resistance with air temperature. The controller converts this resistance into temperature and uses it to control heating, cooling or fan operation.

    ⚠ The sensor works correctly only with a controller whose input is intended for an NTC 1.8 kΩ sensor. An NTC of a different value, a PT100, PT1000 or Ni1000 sensor on the same input will show a wrong temperature.
    Key point:
    This is a simple passive sensor: it needs no power supply, has no electronics that could fail, and the signal is just resistance. The key is to choose the same value the controller expects. NTC 1.8 kΩ is a less common value, so this sensor is usually bought to replace an identical sensor already installed or to meet the requirement of a specific controller.
    Element
    NTC thermistor
    Nominal resistance
    1.8 kΩ
    Signal
    passive, resistive
    Mounting
    in the duct

    Operating principle

    The resistance of an NTC (Negative Temperature Coefficient) thermistor falls as temperature rises and increases as temperature drops. The nominal resistance – in this case 1.8 kΩ – is usually specified at 25 °C.

    The controller passes a small measuring current through the sensor, measures the resistance and calculates the temperature from the NTC curve stored in it. The curve depends not only on the nominal value but also on the thermistor B constant, so it must match the controller setting.

    The probe of the duct sensor is inserted through an opening in the duct wall and fixed so that the sensing part sits in the air stream. This is how supply, extract, outdoor or recirculation air temperature is measured.

    Why use a duct NTC 1.8 kΩ sensor?
    It lets you restore control quickly when a sensor of the same type fails: no need to change controller settings or reprogram the system. A passive sensor needs no power supply, so wiring is simple – two wires to the controller input.

    Technical specifications

    Product type Duct temperature sensor
    Manufacturer / model Not specified / NTC 1.8 kΩ
    Sensing element NTC thermistor
    Nominal resistance 1.8 kΩ (usually specified at 25 °C)
    Temperature coefficient Negative – resistance falls as temperature rises
    Signal type Passive resistive, no power supply needed
    Mounting location Ventilation / air conditioning duct

    Main functions

    • Air temperature measurement in the duct – the controller receives the actual air stream temperature
    • Passive resistive signal – no power supply or additional converters required
    • NTC 1.8 kΩ value – direct replacement for a sensor of the same value
    • Supply air control – heater or cooler control to the set supply air temperature
    • Extract and outdoor air monitoring – data for heat recovery and frost protection
    • Simple wiring – an NTC thermistor has no polarity, so wires cannot be swapped wrongly
    • No active electronics – fewer components that could fail

    How does it differ from similar products?

    NTC 2.2 / 10 / 20 kΩ sensors Same operating principle but different resistance and curve. Not interchangeable – the controller will show a wrong temperature.
    PT100 / PT1000 Platinum sensors with a positive, almost linear coefficient (100 Ω / 1000 Ω at 0 °C per IEC 60751). Require a controller with a PT input.
    Ni1000 Nickel sensor with a positive coefficient (1000 Ω at 0 °C). A different controller input type.
    Active 0–10 V / 4–20 mA sensors Have electronics and a power supply and send a standard signal. The NTC sensor is passive and connects directly to an NTC input.

    Where is it used?

    • Supply air ducts of air handling units
    • Extract (exhaust) air ducts
    • Outdoor air intake ducts
    • Air conditioning and cooling systems
    • Control of heat recovery units and air heaters
    • Building automation (BMS) systems where the controller has an NTC 1.8 kΩ input

    Use by need

    Beginner.
    Check which sensor is installed now or what the controller manual specifies. If it says NTC 1.8 kΩ, this sensor fits.
    Experienced installer.
    Before replacing, measure the old sensor resistance with a multimeter and compare it with the duct temperature – this confirms the value matches.
    Energy engineer / designer.
    In the specification, state not only the NTC value but also the curve (B constant) required by the controller manufacturer, so that NTC sensors from different manufacturers are not mixed up.

    Practical use

    An air handling unit starts showing an unrealistic supply air temperature, and the controller menu specifies an NTC 1.8 kΩ sensor. After disconnecting the old sensor and measuring its resistance, the circuit turns out to be open. With a new NTC 1.8 kΩ duct sensor fitted in the same duct position, no controller settings need to be changed – the temperature is displayed correctly again.

    Pros / advantages

    • No power supply needed – simpler wiring
    • No active electronics
    • Large resistance change per degree – easy for the controller to measure
    • Direct replacement for an identical NTC 1.8 kΩ sensor
    • No polarity
    • Suits most duct mounting points in ventilation systems

    Cons / limitations

    • Suits only a controller with an NTC 1.8 kΩ input
    • The curve is non-linear and depends on the B constant – NTC sensors from different manufacturers may differ
    • On long lines with interference, a passive resistive signal is more sensitive than 4–20 mA
    • Manufacturer data (range, IP, probe length) are not stated for this product – confirm before ordering

    Safety and installation notes

    • ⚡ If wiring in a controller panel that contains 230 V circuits, disconnect the power before work. Installation must be carried out by a qualified electrician.
    • ⚠ Do not connect the sensor wires to supply voltage – this will damage the thermistor.
    • Insert the probe so that the sensing part is in the air stream, not against the duct wall.
    • Install the supply air sensor downstream of the heater or cooler, far enough for the air to be mixed.
    • Route the signal cable separately from power cables so that interference does not distort the measurement.
    • Seal the duct opening to prevent air leakage and condensation.

    Quick selection guide

    NTC 1.8 kΩ
    Passive resistive
    For ducts
    No power supply
    Suitable when you need to:
    • replace a failed NTC 1.8 kΩ duct sensor
    • connect air temperature measurement to a controller with an NTC 1.8 kΩ input
    • control supply air temperature in an air handling unit
    • use a simple passive sensor without a separate power supply
    Check before choosing:
    • which sensor type and value the controller manual specifies
    • whether the controller NTC curve (B constant) matches the sensor
    • the required probe length for the duct size
    • measuring range and protection rating – ask us before ordering
    Important reminder: An NTC sensor cannot be replaced with a sensor of a different value or type (PT100, PT1000, Ni1000) without changing the controller settings – otherwise the controller will display and control to a wrong temperature.
    ☝ Elsprendimai.eu recommends:

    FAQ

    Can I replace an NTC 1.8 kΩ sensor with NTC 10 kΩ or another value?
    No, if the controller is configured for an NTC 1.8 kΩ sensor. A sensor of a different value gives a different resistance and the controller will show a wrong temperature.
    How do I check whether the old sensor is NTC 1.8 kΩ?
    Measure its resistance with a multimeter at a known temperature: at about 25 °C an NTC 1.8 kΩ sensor should read close to 1.8 kΩ. As temperature rises, resistance must fall.
    Does the sensor need a power supply?
    No. It is a passive resistive sensor – the measuring current is supplied by the controller input.
    Does wire polarity matter?
    No, an NTC thermistor has no polarity, so the two wires can be connected either way.
    Are all NTC 1.8 kΩ sensors the same?
    The nominal value is the same, but the curve also depends on the B constant. If the controller manufacturer specifies a particular curve, it should be checked.
    What range and IP rating does this sensor have?
    These data are not stated in the description because they could not be confirmed by manufacturer documents. Contact us before ordering and we will confirm.

    Sources: General NTC thermistor operating principles; PT100 / PT1000 for comparison – IEC 60751. A manufacturer datasheet for this product could not be confirmed. Checked 2026-10-18.

    Duct temperature sensor NTC 1.8 kΩ – replacement for HVAC controllers

    The duct NTC 1.8 kΩ temperature sensor measures air temperature in ventilation and air conditioning ducts and passes it to the controller as a passive resistive signal. It suits only controllers with an NTC 1.8 kΩ input, so check the controller manual before ordering.

    Illustrative image may have been created using AI. The appearance of the product may differ slightly from the image shown. Please refer to the technical specification.

  • Alternative products

    Flexible aluminum air duct | for ventilation | ventilation systems | D100mm | 3m | silver | LAO100  
    Flexible aluminum air duct | for ventilation | ventilation systems | D100mm | 3m | silver | LAO100
    Code: 653
    Price 3.50 € VAT incl.
    ( 2.89 € VAT excl. )
    Add to cart 

  • Subscribtion to new arrivals

    privacy policy

    Information