Combi / shower overheat / trip?

[GCarnegi]

Hi there. Our family have a number of showers in the morning, and I'm finding that after a 20 minute run of our shower (Aqualisa Quartz Digital), when we restart the shower for the next cycle, it starts fine, then runs super cold for a minute or more before re-stabilising.
I guess that means that the hot water in the lines, when the shower switches off, is temporarily overheating the shower, causing it to trip to the cold setting.

I'm thinking that the boiler runs hot while the shower is running, then when the shower turns off, the boiler passively "super-heats" the now static water in the heat exchanger with residual heat, which then moves along the pipes to the digital shower when the next cycle starts, causing the shower to "panic" and trip to cold.

The above assumption may be completely wrong, but any thoughts would be welcome.

 

[Madrab]

It could be .... Alternatively ...... the combi boiler will always take time to catch up and heat the water.

You will get the hot water that was left in the pipes from the first shower to start with and then that will then run cool for a time until the combi catches back up, heats the H/E sufficiently and that hot water then gets to the shower.

 

[dilalio]

I take it that your quartz digital is either non-pumped or has had the pumped setting disabled for combi use? Was it installed prior to/at the same time/or following your combi?

 

[Madrab]

Yes indeedy ....

GC, I took it for granted that it was the combi - high pressure variant of the AL Digital but D's quite right, I should know better and should have checked