110v SSR Bed PWM setting in marlin

Installing 500w 110v silicone heater and read somewhere I should set PWM freq. to lowest setting for this set up. Also saw this commented in Marlin but where is the actual setting? right in front of my face I'll assume. What should I set it at?

Disregard. I dont think anything needs to be changed. Its doing very well as is (see attachment). Probably need to run an autotune on the hotend again though. On a side note Im trying some 12v 50w heaters
i got off ebay which are the same dimensions as the 30w. These things kick butt. 25-370c in a little over 2.5 minutes. 25-160c in 2 minutes for new bed heater. No more waiting for temps .........yippee