"Mike Holmes" wrote in message
ups.com...

Note that if you have a 300L store at 75 degrees, and the PHE minimum
differential is say 5 deg that only give you 15 degrees, to play with or

Differential at 5C? Are you serious?

18.9MJ or about 4 mins. With real time replenishment from the boiler you
may extend that to 6 min. So long as the showers are thermostatically
controlled however you an cope with a much greater fall in store
temperature. Obviously the more modest the shower flow rate requirements
the better, and the more boiler power available the better.

Very good point about the capacity requirement for a high flow rate
like this - thanks for the heads-up on that. I shall have to invest
in a higher capacity tank for sure. My existing one is just
96litres! Good opportunity to get a direct cyclinder suited to the
job anyway... and the total cost is still a tiny fraction of the
Pandora equivalent... and only a little more than a decent pump which
can deliver a similar performance hot water pressure and flow rate...
which happens to use about 1.5kW of electricity when operational!!

Have two tappings at the bottom and run the CH off this. Have TRVs on all
rads and a use a Grundfoss Alpha on the CH circuit. Then no room t/stat
needed.