Combi Boiler & Mixer Tap/Shower

[markmcd]

Hi,

I am I having an issue with the mixer tap/shower in the house I have just moved into. The tap looks like the one below: -

http://www.sobathrooms.com/bathroom...bath-shower-mixer-taps-37193-16221_medium.jpg

I have changed the shower hose and head out for this: -

http://www.screwfix.com/p/swirl-xeron-shower-kit-modern-design-chrome/89437

The problem is that the tap works fine and will fill a bath of hot water from the Worcester Junior 24i boiler no problem. However when I change to the shower part the water only runs hot for 30 secs then the boiler switches off. I have since found that when I turn on the close by sink hot tap that the boiler will come on again and I will get a hot shower!

Is there some sort of minimum requirement regarding the flowrate or something that makes the combi boiler think that it no longer needs to heat the water? The water does not stop - just comes out the boiler cold.

Thanks in advance.

 

[ChrisR]

Usually it's sludge in the boiler, especially if the water heating eventually comes back on again. Low flow >> boiler overheats >> switches off.
Cleanable by a boiler man, DIY maybe.

Otherwise could be eg a flow switch.