Grumpy_Mike:
So from the power rating the heater element has a resistance of 38.4 ohms.
Apply that with 24V and you get 0.625 Amps. That is a power of 15 watts.
And that's exactly what we should expect with a fixed resistance load. If you only apply 1/10th of the voltage you get 1/10th of the current and since power still equals V x I you get 1/100th of the power (15W vs 1500W).
Steve