"David W.E. Roberts" wrote in message
...
Hi,

how to get the most power from your power shower:

Target temperature (for argument's sake) 38 degrees C (red stop on
thermostatic control).

(1) There are two pressurised feeds, hot and cold
[Obvious]

(2) Maximum flow should be when both are used equally.
[Logically, if the hot water is at 38C then no cold will be added, and
shower will only have 50% of the potential water flow available]

So optimum set up is when (Cold Temperature) + (Hot Temperature) / 2 = 38C

(CT + HT) / 2 = 38
(CT + HT) = 76
HT = 76 -CT

Assume mid winter cold tank temperature is 4C.

HT = 76 - 4 = 72

Assume mid-summer cold tank temperature is 15C

HT = 76 - 15 = 61C

Loads of variables, though.

This assumes your cold tank is reasonably insulated and normalises through
the night for the morning shower.
This ignores the drop in summer cold tank temperature as fresh water flows
in from the underground main.
This ignores the fact that the pump can probably deliver more water than
the
shower can accept.

Conclusions:

(a) To ensure best shower performance, make sure the flow rate of the pump
is higher (I would guess 30%-40% higher) than the maximum flow rate of the
shower.
(b) There are potential benefits in raising the hot water temperature in
winter, but beware of scalding at the taps.
(c) Strange what you think about in the shower

Cheers
Dave R

P.S. the truly sophisticated will have a hot tank thermostat which also
has
a sensor in the cold header tank and will maintain a differential rather
than an absolute temperature





This doesn't take in the fact of losses through transfer from water storage
tanks and the variable temperature of the hot and cold water storage tanks
refilling from their respective supply when water is drawn from them. This
can never be taken as constant.

A shower outlet will only allow a certain amount flow rate no matter at what
supply pressure (all the little holes in the head can only take so much) so
the shower should be set to allow optimum flow from the actual outlet. This
reduces the effect of it actually choking itself with excessive push back
forces (the equal and opposite forces thing).

The temperature of the hot supply should be set 12 to 15 degrees C above
normal body temperature (37degrees C or 98.6 F) to allow for blending and to
give a variable control for differing personal needs and wants, but never
being allowed to get to the point of being able to scald the skin. As we
age, we lose the ability to regulate temperature properly, so it is safer to
have the maximum temperature of the supply set to a safe and with standable
level. This applies to children as well.

The pump used should be fixed to allow an output of only a third of the
volume of the water that is supplied to feed it. This reduces the
possibility of the pump ever running dry by emptying the supply tanks. The
tanks should also be set to allow an output of only a third of the volume of
the its supply. Pumps should always be supplied from tanks which allow the
water to settle and become still before being drawn off to the pump. The
stops the effects of aerated water being drawn into the pump and causing
spluttering of the water at the outlet due to the build up of trapped air
within the impeller. This also reduces the build up of scale within the
pump and mixing valve by keeping a constant flow of water and not a mixture
of air and water.

Yes, you're right, it is amazing what you think of while standing in the
shower. :-))