I would surely like to find some that did NOT have automatic zero-crossing switching.
Well all scr/triac based SSR are going to be zero-crossing switching from on to off state as that is the only way to turn off a triggered and conducting scr. However the the turn-on can be either random or zero based I guess on the design of the triggering circuit of the device. Not sure if it is always clearly stated in many SSR datasheets or not what the turn-on charactristic are of the device. I would assume that lots of high power random switching would generate a lot of harmonic garbage in the local power wiring?
Lefty