Selection and Placement of PTC Heaters
in Air Conditioning
PTC Electric Heaters: Heaters that use PTC thermistor elements as the heat source. PTC thermistors are usually made of semiconductor materials, and their resistance changes drastically with temperature. As ambient temperature decreases, PTC resistance decreases, and heat generation increases accordingly. They can be classified by material into ceramic PTC thermistors and organic polymer PTC thermistors. Ceramic PTC thermistors are used in auxiliary electric heaters for air conditioning. Because PTC thermistor elements have the characteristic of increasing or decreasing resistance with changes in ambient temperature, PTC heaters are energy-saving, temperature-controlled, safe, and have a long service life. Currently, there are two types of PTC heaters: air-cooled and water-cooled. Water-cooled heaters are more expensive and have a more complex structure, but they are safer than air-cooled heaters.
PTC Installation Location in HVAC Systems
1. The PTC heater must be installed after the heating element; otherwise, its heat exchange performance will be reduced.
2. The PTC surface temperature can reach 160°C, while the plastic casing can only withstand a maximum temperature of 110°C. Therefore, contact between the two should be avoided. Generally, it is fixed to the casing with screws, and the heating surface should not come into contact with other plastic parts.
3. The power consumption of the PTC should not be too high. Taking the PSAX7 as an example, its specified power consumption should not exceed 1000W, and the airflow passing through the PTC should not be less than 250kg/h.
4. The distance between the PTC and the heating element should be greater than 4mm. A certain angle (0-10°) is acceptable. When the PTC is very small, the pressure drop needs to be improved; it should be placed as shown in the diagram below. The first method cannot be used because it may generate eddies.
Summary
Automotive HVAC air PTC heaters, as an indispensable heating component in current new energy vehicles, have mature technology. Their successful application relies on careful layout design (integrated into the internal air duct of the HVAC assembly), reliable integration solutions (high-voltage power supply and refined PWM control), and strict control over various key considerations.
Safety is the cornerstone of its design, ensured by the self-limiting temperature properties of PTC materials and multiple electrical protections. Efficiency is its biggest challenge, directly impacting the winter range performance of electric vehicles; optimization focuses on control strategies and system-level energy management.
Looking ahead to 2026 and beyond, despite fierce competition from high-efficiency heat pump technologies, PTC heaters, with their unparalleled low-temperature performance and cost advantages, will play a crucial supporting role in the integrated architecture of "heat pump + PTC". Technological innovation will continue to focus on integration, intelligence, and efficiency, ensuring that PTC technology maintains its place in future automotive thermal management systems.
