Paul,
It is recommended, that the temperature of Hot Water be no higher than 55*C(130*F), at the tap(Faucet) when it gets to it's hottest point.
Which is rather difficult to set up, because the thermostat controls the water in the Cylinder, not the tap temperature!.
Other side of the coin though, I saw heaps of cylinders that were wound right up to 90*C(195*F)!. [Linked Image]