Combi boiler hot water probs ...

Hi all

I'm baffled (not hard, I know !) My daughter has an Alpha CB24X -

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boiler in her house, which is a retrofit in place of an original indirect storage system. It was done before she bought the house. Unit is wall mounted in the kitchen and has two large-bore pipes heading up through the ceiling (CH flow and rtn ??) and four 15mm pipes heading down ( gas in, cold in, overflow and hot water out it would seem from the manual).

House is typical smallish semi from about 15 years ago, and the bathroom is just above and to one side of the kitchen, so pipe runs to upstairs not long - probably 5m max.

So she calls me tonight and says that her shower is only warm (it's an in-wall thermo mixer fed from the hold and cold feeds to the bath taps) and that she tried a bath the other night, and that too was only warm. I asked her where she had got the hot water thermostat set on the boiler, and she said right up at No9, but that she used to only have it at No5, and the shower was fine. Neither she nor her husband normally take baths, and the shower was in when they bought the house, and has been fine up until now. A few months back, we fitted a new bath with new taps, and also a new basin and taps, but all the existing pipework was left intact, the only change being that the bath and basin tap feeds were just cut a few inches below the original taps, and flexi tap connector to push fits installed to make the connections to the new taps. No service valves were fitted in these feeds, and everything has worked fine since the job was done, until this problem developed.

I then asked her how the kitchen water was, and she said that it was too hot to hold your hand in. Initially, I thought that she might be looking at an issue with the temperature of the incoming water, but the fact that the downstairs water was very hot seemed to knock that one on the head.

I went over there to have a look, and she is dead right. The downstairs water is blisteringly hot, the bathroom water - shower, bath tap and basin tap - is best described as feebly warm. Given that there only appears to be one hot water outlet from the boiler, which presumably splits somewhere under the kitchen worktop into downstairs and upstairs feeds, what on earth could be causing this odd symptom ?

Any suggestions gratefully received ... d:-\

Puzzled Arfa