FYI I asked this same question in TouTube before I found this page!
Electronoobs this is AWESOME!! Thanks for putting this up and it's exactly what I am looking for to make a homemade candy maker and keep the candy at temp to increase my working time by keeping the candy hot in a hopper.
One question is I am in the US and 120VAC. I think this will work if I understand because the photocoupler should find the zero cross point no matter the AC voltage. The one thing I know I would have to change is 'maximum_firing_delay' to my electric. Is that correct? If not what would you change for 120VAC? The BTA16 TRIAC maybe?