Line voltage relay wiring advice

[lleo]

So I have two separate circuits. To keep it simple, lets say one circuit is a ceiling light with a switch leg. The second circuit has its separate load, and I would like to have this load on whenever the light is on. Among others this can be achieved with a line voltage relay turning on the second circuit whenever the first one is energized.
 
The cables from the two circuits are running adjacent to each other in my unfinished basement, so easy access.
But what are the wiring practices to install a line voltage relay in the joist space of a basement ceiling?
I imagine that this will have to be in an electrical box, but what about the relay, are there any wiring sockets for line voltage relays?
Is this to be mounted inside the box or outside? Also what are the issues around two circuits in one electrical box?
Any pointers, suggestions are welcome, and thanks!
 

 

[RAL]

You need to mount the relay inside an electrical wiring enclosure.   Something like this one.
 
You don't really need a socket for the relay.  Just get a contactor that has screw terminals and/or spade lugs and is meant for this sort of thing.
 
Here's one example.
 
When I have two circuits in one enclosure, I label that fact on the enclosure to make sure people are warned.

 

[az1324]

Functional Devices - RIB01P + Handy Box

 

[lleo]

Thanks you both, this was helpful, exactly the info and clues I needed.