Vokara 29he

An audiologist won't help you at all with your hot water!

I'm assuming you mean heating? Brian I'm sure there is a joke here, but I'm also sure others will poke fun at it as its from Home owners clubs interface which is a joke in itself. Brian

Joking aside, this sounds like a blocked or scaled up DHW FPHE.

S.

Or possibly a flow switch? Should be easy to check whether the boiler responds to the call for hot water, most simply with the CH off.

Sounds reasonable. Running hot for 30 seconds when the CH is on sounds like residual heat in the heat exchanger and the boiler not firing at all when HW is called for.

We are assuming that HW is actually turned on at the boiler. :-) There are usually separate controls for CH and HW flow temperature, and often separate controls to enable CH and HW on the boiler; an alternative explanation could be that the boiler is accidentally configured not to supply hot water, only cold.

Always double check things like this first. On the lines of "Is it plugged in with the switch turned on? Can you see any lights?" when dealing with computers.

Cheers

Dave R