# Choice of AC/DC power supply for PTC heater with inrush current

I want to power 2x PTC heaters mounted in parallel with a 24VDC power supply (this one). If possible I would like to avoid using a current-limiting system to handle the inrush currents. The specs of each heater is:

• 24VDC
• Inrush current: 8A
• Stable current: 0.2A

For 2x heaters I'm then expecting:

• Inrush current: 16A
• Stable current: 0.4A

This PSU is rated for 24VDC/10A. The specs sheet says:

Inrush current[A] - ACIN 230V - 40 typ (I0=100%)(at cold start Ta=25 degrees C). The value is primary surge. The current of input surge to a built-in EMI/EMC Filter (0.2ms or less) is excluded.

I believe "40 typ" means 40 * current rating = 40 * 10A = 400A? This PSU could then handle a 400A inrush current from the load? If yes, for how long?

Is my reasoning correct? Thanks for any hint

• AC inrush of 240V*40A = 9600Wp with a DC inrush of 384 W and a steady-state load of 9.6W with a \$100 power supply , that's a 100x start surge. for a 60 Ohm load when hot. What's wrong with this picture? Can you design a better solution or are you in a rush. ? pun intended ;) Dec 4, 2021 at 4:50