I have a Worcester Bosch Highflow 400 combi, about 8 years old.
All was well until after we came back after a fortnight away. Now when a hot tap is turned on, the water flows hot after a few seconds, as you'd expect, but only for a second or three. It then goes tepid and takes another ninety seconds or so to regain the required temperature.
So, what's going on? Duff thermostat, thermostat phial, or what?
I have an even older one (21) and get a similar issue - It is due to the DHW temp overshooting due to the heat in the exchanger transferring into the heatbank after the thermostat has shut down. It then takes a while to realise that the gas should be turned on again due to the thermal inertia. (Well - that is what I think.) It seems more noticeable at low temp settings.
In message , John writes
Thanks for the input.
Does anyone know the way to fix it?
Have you tried a higher setting on the DHW Stat? A low setting seems to make mine a bit slow to realise some DHW has been drawn off. I guess boilers with a flow sensor are better in this respect.
another thought - I wonder if some conductive heatsink compound in the thermostat pocket would aid heat transfer to the phial. I have often thought of trying it but haven't got a round tuit
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