Thermostatic shower - quick sanity check.

Static pressure 3.0 bar.

Flow from cold outside tap ~17l/min.

Accepted that there will have to be flow restriction on the cold taps in the house to prevent loss of hot water pressure.

Just looking at mixer valves.

"Water minimum flow rate For best performance within the specified running pressure range a minimum flow of 8 litres per minute should be available to both inlets."

Now does this mean that you need a total flow of 16 litres per minute evenly distributed between the hot and cold?

In which case it is just in spec. with a 17litres per minute total flow.

Or does it mean 8 litres per minute shared between the two outlets which is well within spec.

I think it is total flow of 16 litres per minute, but just double checking.

Cheers

Dave R

8 litres per minute, the appliance MUst be capable of raising the water temperature to 52°C (minimum).

IME bar mixers are not that "thirsty"... If you look at the graph at the end of the instructions it certainly suggests that an inlet pressure of

3 bar will yield 18 lpm of output - but that is qualified with "Flow control fully open, Open outlet - no hose or showerhead connected".

So in reality I would expect it to need at most 10 lpm (and probably a bit less) of total water flow hot and cold combined. That ought to be doable on a 24kW combi.

Note you can get some odd interactions with combis, when they are at their limit power wise - these can introduce some large "dead" zones where the temperature control does not seem to do much. The boiler will be able to do around 10 lpm of hot water mid winter when running flat out - but that will be at about final use temperature, and not the 55 deg that the shower maker is recommending. However asking for less water will allow it to do it at closer to the suggested 55. (a quick calculation suggests that it should be able to provide nearly 7 lpm at

55 deg with the inlet water at 5 deg (assuming the 24kW is genuine output power and not just inlet)

I suspect it will "just work". If you have any problems, then throttling the shower slightly (or fitting a more restrictive shower head) will fix em.