Electric Fan on/off temps

[Lippyp]

As I'm putting the engine back together I want to install a thermostatic control for my electric fan, at the moment its just controlled by a manual switch on the dash which is OK unless I get forgetful. Initially to turn the crappy plastic japanese one thats now on the rad and then to run the new bigger Volvo T5 fan that will be going on as soon as I can bend up a shroud for it.

I'm going to use one of these



Its a billet anodised hose adaptor from a company over here that makes them for Landrovers, it will fit in the top hose and then take a standard radiator electric fan switch (22mm thread) that I can buy for a couple of quid at various temp ranges from any parts place over here. My top hose is already cut in half with a bit of old exhaust pipe in the middel at the moment so its n o hassle at all to replace that with this better looking piece and then wire it up to a relay and boom, thermostatic switch. I might also wire it up to an led in the cab and an override switch so I can pre-empt it if I get into heavy traffic and just put it on permanently.

What I need to know is what temperature it should switch on and off at? Like I say its going in the top radiator hose and its a mild 350, top temperatures over here tend to be mid to late 20c's maybe low 30c's for a few days each summer. (sorry, thats Metric we haven't used F here since I was a kid)

My new 9well junkyard) fan