If you look at the picture there is a U shaped depression on the right side
There should be one on the bottom too
This is the same size a electrical conduit ("pipe" you run wires in )
Would recommend you surface mount timer exactly as you show in the picture but run the wires in conduit instead of loose
There should even be a fitting (which Murphy's law says your local hardware store will not have) that sits in the place of the old switch with a conduit adapter opening facing upwards
@SHL Thanks for your help.
I did as you described and it works great.
I ended up just putting the timer directly above the switch and rubbed down a small hole in the top of the switch for the wires to come out and go directly into the timer w/o being exposed...
One question..
The IN wires for the heater were not long enough to reach the timer to double on to the IN screws. Also, the wires are thick and it looks like I wouldn't be able to fit 2 wires under one screw.
Can I simply take the 2 IN wires and have them split off to the heater (before they enter the timer)? So half would go to the boiler timer and half to the heater (Like a "Y")
In other words.. I would take the brown and blue wires that run from the wall into the IN of the timer, and cut them halfway. Then attach the 2 halves of the blue as well as the blue for the heater all together so everything has power (and then do the same for the brown).
I'm not sure if I am explaining myself well. LMK...
Thanks!!