We had a similar issue after about 5 years with a T80i: switches kept burning out. Solution: replace the switches, and add (in the wall cavity behind the shower unit) a couple of industrial contactors to handle the 40 amp loads. The original heating coil wires were taken to the contactor trigger circuit, the contactor switched power was returned to the heating coils. This results in all the Triton swiches and circuits handling only a miniscule triggering current: the contactors do the heating coil switching. Shower has run trouble free ever since. Show this to your friendly local electrician and s/he will understand it.
Wayne, June 2006