Immersion boiler timer

Hi,

I have just ordered a timeguard timer switch, 16a up to 3.68kw timer. 
 

I have wired it up to the 3 kw immersion element

This runs off a 16a breaker at the fuse box.

There is an isolated on off switch which I have kept then taken a wire to the live, one to the neutral and then earth to the switch input 
 

wired the live and neutral to the switch output. And joined the two earths and wired into the earth in the switch.

All seems to be fine and working.

My question is about volt free switching. The timer has the option of being volt free, (by removing the link I think). Then it would have to wired it differently.  
 

does the immersion element on the boiler need to be volt free. I tried to figure out this but I’m not sure. 
 

thanks I’m advance for any advice, I just want to check I have this correct. 

No, what you’ve done sounds correct. 

Thanks for your response, I think I have worked out where you would use the contact free switching.

if you had the timer on the mains, but the electric circuit you were switching on was on a different voltage.

you can open and close that circuit with the switch, but the mains would never power that circuit, only the switch. That circuit would have its own power source set at a different voltage to the mains.  Like a 12v lighting Circuit or something similar.