In message .com,
charlieB writes
I presume the duty cycle is in the shower instruction manual.

The duty cycle almost certainly originates from the safety
certification of the shower. As part of the safety testing the
temperature of all the internal components and insulation is measured
and checked that it doesn't get too hot. most high power domestic
electrical equipment is operated on a duty cycle, this gets written
into the instruction manual and then the duty cycle is followed during
safety testing

the limiting temperature is the worst case component at the highest
ambient (air)operating that the shower is in - which will be warmer
than your typical bathroom temp

Unless you're running the shower for a very long time on a hot day I
wouldn't have thought you'd have a problem - other than electic showers
are usually crap :-)

THe OP isn't talking about an electric shower now, they are talking
about a power shower. We have a power shower that has a similar duty
cycle - a Aqualisa aquastream . This is one of the all in one type, with
the pump a small low voltage unit inside it.

In normal use we wouldn't go over that anyway.

But I would imagine that if this was really an issue, then a standalone
pump unit would have a much 'better' duty cycle
--
Chris French