Thermostat rant

[Eric Alan]

This is really interesting talk, but I find the second Tstat to be somewhat useless especially if it is of less quality then the primary one ?

It's less quality because its purpose is not to control the temperature continually - that's what the primary does. It's only purpose is to prevent severe injury in the event of a failure (in the on position) of the primary thermostat.

If it fails on "on" then if for some really bad luck the primary Tstat also fails you will still get the same problem ?

Exactly. It takes TWO failures for this to happen though, which is significantly less likely.

Would it not be simpler to make sure the Tstat goes off if it does break ?

Simple in theory, yes. In practice? Not so much... If it were, it would have been done already.