Power Shower Cold, Tap Still Hot!

[exparrot]

I've got a Bristan 1000xt power shower which draws from a vented hot water cylinder and cold water storage tank, which will happily run doing its thermostatic thing excellently for at best 10 minutes. However, after that it starts to quickly get cooler until the icy chill forces you to abandon all hope of ever feeling warmth again, never mind any body else being able to use the shower immediately afterward.

Now, I wouldn't have a problem if the root cause was depletion of the hot water cylinder resulting from the immense flow of this mighty power shower. Alas, the 1000xt is spec'd at a flow rate of 10l/min (of which hot would be expected to be ~6l/min), so it's not exactly feasible that it is getting through an entire cylinder's worth of hot water in that time. This is additionally evidenced by the continued presence of hot water when turning on the bathroom tap.

Given that the shower and taps share the same outlet from the hot water cylinder, I can only fathom that there is an issue with the thermostatic control on the power shower. Does anybody have experience with similar issues or any other thoughts?

 

[muggles]

I'd suggest looking for a partial blockage or airlock in the hot supply to the shower. It should be a dedicated supply from the cylinder

 

[plastic_peanut]

We had a similar issue at our last house although no lt to the same extent with temperature. Our bath never got particularly hot but the taps could take your skin off some times.
After a lot of checking and head scratching I swapped out the caleffi thermostatic valve fitted off the hot water cylinder. The old one was full of sludge and didn’t adjust particularly well. It cured the problem but still odd I’d didn’t effect all outlets. Maybe something to do with flow?