I've read that the low voltage wires should be rated for 600V, if in the same box.
I'm sure there is a 'right' and better way to do this, though, as I've seen relays mounted on the outside of line voltage junction boxes.
It's difficult for me to determine which relay you are using, from that spec sheet link.
If you don't get an answer here, call Automation Direct for some guidance or additional literature. They were very helpful with me choosing terminal al blocks.
TB A+ Partner Believe nothing, no matter where you read it, or who said it, no matter if I have said it, unless it agrees with your own reason and your own common sense. -Buddha
