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How to choose temperature sensors in the HVAC industry? Understand 4 key points in 5 minutes
2026-04-21
Choosing the wrong temperature sensor can lead to inaccurate temperature measurement, or even cause the entire building automation system to malfunction. The selection of Temperature Sensors in the HVAC industry (central air conditioning, heating, ventilation) is not that complicated - mastering these 4 core points is sufficient.
🌡️ First, determine: What medium to measure?
| Medium | Recommended Sensor Type | Key Requirements |
|---|---|---|
| Water / Ethylene Glycol Solution | Insert-type with protective sleeve Temperature Sensor | Sleeve material: Brass or 304 stainless steel |
| Air (Ventilation Pipe) | Ventilation pipe type temperature sensor | Probe length should reach 1/3 to 1/2 of the width of the ventilation pipe |
| Indoor Environment | Wall-mounted temperature sensor | Aesthetically pleasing appearance, avoid direct sunlight position |
| Outdoor Environment | Rainproof wall-mounted type | Protection level ≥ IP65 |
Summary in one sentence: Use insert-type for water, ventilation pipe type for air, wall-mounted for indoor environment, and rainproof wall-mounted for outdoor environment.
⚡ Additional Selection: Temperature Measuring Elements and Output Signals
The most commonly used temperature measuring element in the HVAC industry is Pt100 (platinum thermoresistor), which has high accuracy, good stability, and a favorable cost-performance ratio.
How to select the output signal? Refer to this table:
| Output Signal | Transmission Distance | Applicable Scenarios |
|---|---|---|
| Pt100 resistance signal (three-wire system) | ≤50 meters | Controller has its own temperature measurement module, with the highest accuracy |
| 4-20mA | ≤500 meters | Most common, strong anti-interference, suitable for long-distance transmission |
| 0-10V | ≤100 meters | Common in building automation systems (BAS) |
| RS485 Modbus | ≤1200 meters | Used in intelligent buildings, suitable for multi-sensor networking |
Selection suggestion:
Connect to DDC controller → 0-10V or 4-20mA
Connect to PLC → 4-20mA is the most reliable option.
Uncertain → 4-20mA, the most versatile option
🔩 Key Details: Sheathing and Precision
🛡️ Regarding the sheathing (protective sleeve)
For water pipe Temperature Sensors, it is recommended to always use a sheathing. The benefits are:
- Protect the sensor from being corroded by the medium.
- The system can be operated without stopping to replace the sensors.
- Material: Regular brass for water systems, 316L stainless steel for corrosive media
🎯 Regarding accuracy
The Pt100 is classified into Grade A and Grade B according to national standards:
| Accuracy Grade | Error at 0℃ | Applicable Scenarios |
|---|---|---|
| Grade A | ±0.15℃ | Hospital clean rooms, data centers, precise control |
| Grade B | ±0.30℃ | Ordinary offices, shopping malls, residences |
Selection suggestion: For most HVAC projects, Grade B is sufficient. For cooling and heating measurement, Grade A is recommended.
📋 Quick Reference Table for Selection (For Direct Comparison)
| Application Scenario | Thermometer Element | Output Signal | Installation Method | Precision |
|---|---|---|---|---|
| Chilled Water Supply and Return Water | PT100 | 4-20mA | Type + Sheath | B Class |
| Hot Water Heating | PT100 | 4-20mA | Insertion Type + Sheath | B Class |
| Air Conditioning Supply/Return Air | PT100 | 0-10V | Chamber Type | B Class |
| Indoor Temperature | PT100 | Resistance / 0-10V | Wall-mounted Type | B Class |
| Outdoor Temperature | PT100 | 4-20mA | Wall-mounted Rainproof Type | B Class |
💡 Remember These 3 Sentences Before Purchasing
- 1 Determine Installation Based on Medium: Insertion Type for Water, Chamber Type for Air.
- 2 Distance setting signal: Use resistance for short distances, and 4-20mA for long distances.
- 3 Pipe with protective sleeve: Saves money and is convenient, allowing maintenance without stopping operation.
🏢 About Us
Weilian Electronic Technology specializes in temperature sensors for HVAC and industrial applications. Our products cover:
- Water pipe / ventilation pipe / indoor and outdoor temperature sensor
- Pt100 / 4-20mA / 0-10V / RS485 output
- Support customizable cable length and probe size
Plug-in HVAC temperature sensor
