Choosing a PTC
I. Introduction to PTCs
PTC electric heaters: A type of heater that uses a PTC thermistor element as a heat source. PTC thermistors are typically made of semiconductor materials, and their resistance changes dramatically with temperature. When the ambient temperature drops, the PTC's resistance decreases, while the heat output increases accordingly. Based on the material, PTC thermistors can be categorized into two types: ceramic PTC thermistors and organic polymer PTC thermistors. Ceramic PTC thermistors are used in auxiliary electric heaters for air conditioners. Because PTC thermistor elements increase or decrease in resistance with changes in ambient temperature, PTC heaters offer energy-saving, constant temperature, safety, and a long service life. Currently, there are two types of PTC heaters: air heating and water heating. Water heating is more expensive and complex, but is safer than air heating.
There are many types of electric heaters. Several PTC specifications are listed below:
II. PTC Installation Location in HVAC Systems
1. The PTC must be installed behind the heater core; otherwise, its heat exchange performance will be reduced.
2. The PTC surface temperature can reach 160°C, while the plastic housing can only withstand a maximum temperature of 110°C. Therefore, contact between the two should be avoided. It is generally fixed to the housing with screws, and the heating surface should not come into contact with other plastic parts.
3. The distance between the PTC and the heater core should be greater than 4mm. A certain angle (0-10°) is acceptable. If the PTC is very small and the voltage drop needs to be improved, it should be placed as shown in the figure below. The first method should not be used because it may generate eddy currents.
Automotive HVAC air PTC heaters are an indispensable heating component in current new energy vehicles, and their technology is quite mature. Their successful application relies on careful layout design (integration into the HVAC assembly's internal air duct), a reliable integration solution (high-voltage power supply and refined PWM control), and strict adherence to key considerations.
Safety is the cornerstone of their design, ensured by the PTC material's self-limiting temperature characteristics and multiple electrical protections. Efficiency is the biggest challenge, directly affecting the electric vehicle's winter range. Optimization focuses on control strategies and system-level energy management.
Looking ahead to 2025 and beyond, despite facing 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 "heat pump + PTC" architecture. Technological innovation will continue to focus on integration, intelligence, and efficiency, ensuring that PTC technology maintains its place in future automotive thermal management systems.
