@John_Ridley Indeed. Good point about the duty cycle while heating. PCB heaters have limitations though much of what users have issues with are power supplies. The cheap supplies just can’t keep up.
@John_Ridley Re: 24V and the 11A Polyfuse: The voltage rating only comes into effect when there is a short (ie: the full supply voltage ends up across the PTC). In such a condition, the PTC gets way too hot before tripping (a PTC takes ~20 sec to trip from cold), which can actually make the PTC catch fire!
This is why I hate PTC’s, because they are supposed to do their job in a fault situation. If anything is out of spec then the behaviour may not be as you expect, and the definition of a fault is “out of spec” IMO. As it is, ~20 to trip in the presence of a fault is too long also IMO.