On 03/11/2018 16:55, George wrote:
On Saturday, 3 November 2018 13:56:29 UTC, George wrote:

snip

Also, on a different subject I have been living in a Mobile Home
where I have my workshop and there is a gas heated water heater and
I bought a water pump that comes on when I open any tap, this works
fine except in the shower and as the pump starts and stops the hot
water varies between boiling hot to freezing cold and I use a lot
of gas and water dodging in and out of the water spray. Does
anyone know the answer to this as the only thing that impoves the
situation is by having the demand relay operating very quickly,
which cannot be good for the relay contacts?

Thanks George.

Thanks Bill, The pump came with a tank with a diaphagm but I have
lost the instructions to set it up so I pumped it up to 20psi not
really knowing what it should be set up, - the switches seem to vary
the pressure between 10 psi and about 30, that was with no water
pressure in the system, what do you think it should be? The water
temperature which varies with the pressure, seems to be all over the
place and I have to continually adjust this. Regards George.

A solution is to use an accumulator (expansion vessel) and pump, but
then to use a pressure reducer to cope with the fluctuations of
pressure. You might have to step up the pressure switch and make sure
the accumulator can cope.

I would set the accumulator pressure to be just below the expected
minimum water pressure, ie when the pump kicks in. 10 to 30psi is a very
wide range. I would expect less than a 2:1 range.