Morning Al,
We have 3 children, 6, 4 and 2, so there are showers and baths most if not every day, the bath as noted earlier is a larger size and holds around 365litres, these days my wife doesn't have many baths (theres no time!) but we shower daily as do the kids, sometimes twice for the kids depending on circumstances
Typically showers use a lot of water - plug in the bath shows that water level will be a a quarter to a third full for parents and normally half full for the kids (thats three kids all showered together) its less than a 8th when single kid is "emergency" washed.
Shower is direct feed thermostatic from mains pressure lpg boiler which is a Worcester bosh 28kW condensing boiler- no hot water cylinder, 22mm dia copper pipe work feeds the bath and shower.
To give you an idea of the flow we have the boiler cannot heat the water fast enough to fill the bath with water above 18degrees C if the tap is opened fully, so we have to throttle the flow by around half to a third to get water at "hot" bath temps.
So while we don't bath often I need to ensure in future that the system can fill the bath adequately so that when the day comes that my wife can have a relaxing bath again - that its available through the ASHP system. As the mother of three very active boys thats the least I can do for her.
Thats where the 300ltr direct unvented hot water cylinder requirement came from which I think also benefits the heat pump which like to run low temperature but for long cycles?
Then add in to that the fact that the cottage is small by modern standards and the HWC would need to be outside in a lean to next to the ASHP through necessity.
I have looked at the Areston Nuos and similar systems before but I believe the system relies on the warm air drawn from the interior of a building to compliment a smaller ASHP to get the temperatures required - this could still be done with some 5" vents cored through the cottage walls noting that the wall in that section is slate and a solid 3ft 6" thick plus another 6" EWI. These systems with clever adaptation of the vent lines and valves can direct cold air outside in winter and inside in summer to provide cooling, I have no feel for how these units compare with the split systems in terms of reheat times. They also look simple to plumb in from my limited plumbing experience and so a local plumber would be able to do all the pipework to and from.
The only detraction I see is that they would cause a pressure drop in the house and therefore a potential increase in draughts around feet from air ingress leakage paths.
The split systems come in larger sizes (if reheat is an issue) don't induce draughts in the house but also don't offer cooling in summer - is that a real problem - doe we get enough hot summers in North West Wales to worry about this ?
Thats about the sum of my thinking so far other than we are West facing with a southern Gable end for the system to be mounted, air temperatures range from 5 to 18 degrees average with peaks in the low 20's and in winter we get perhaps 5 days of zero or sub zero temperatures.
minus three last night for instance.
Moxi