Worcester Hot Water suddenly started to not heat

[James1979]

I have a 18 motnh-old Bosch Worcester boiler. It works brilliantly and both heating and hot water have been in constant supply whenever needed. (no heating required at the moment of course!)

Two nights ago I noticed the water from the bath hot water tap was very hot (as usual) to begin with but very quickly turned cold - well, lukewarm at best.

This was the first time this had happened so I check the boiler and the pressure had dropped to 0. It has an integral charging link so I re-pressurised the boiler and thought all was well.

The boiler has kept it's pressure. The shower water continues to heat perfectly (it is also heated from boiler - not electric) but I still have the same problem with the taps for the bath and all sink taps including kitchen. It starts off very hot and after a few seconds turns to lukewarm water and doesn't heat up again.

I'm guessing the pre-heat feature is what's heating the water to start but why is it losing heat when the shower is still working?! Could be it be too hot and the cut-out is operating?

Any geniuses out there who could help?

Much appreciated.

 

[gigz]

Turn your bath tap on then go to the boiler, does the green light stay on where the flame symbol is ? Or does it keep going off and on ?

 

[James1979]

Thanks for the reply - yes, the boiler fires correctly when there's demand and the light stays lit the whole time the tap's on.

After some more fiddling around today I discovered something odd that may help - if you are running the hot bath (or sink) tap and the hot has turned lukewarm which it does after 30 seconds or so and then also turn the shower on at the same time, the shower water is hot as it always but the bath tap water also becomes scolding hot at the same time!

I thought it might have been due to the taps having too much pressure and the boiler not being able to heat it in time but that can't be true if it can heat the shower and tap simultaneously! Just very bizarre it needs the shower turned on at the same time to heat it.

Does that help diagnose?

Many thanks again,